Radial Truck Tire And Retread Service Manual · PDF fileForward This manual was prepared as a...

Radial Truck Tire

And Retread

Service Manual

Section Title Page1. Radial Truck Tire Terms 5

Cross-Sectional View of Typical Tire 62. Tire Selection 8

Tire Selection Process 9Tire Selection Process Work Sheet 16

3. Mounting Procedure 19Safety Instructions 20Wheel Inspection Guidelines 20Lubrication 20Tire and Rim Cleaning 21Tubes and Flaps 22Assembly of Tire Tube Flap 22Tubeless Tire Mounting 23Installation 23Demounting 24Matching of Duals 25Spacing of Duals 26Spacers 26Proper Matching of Rim Parts 27Safety Precautions 28Mounting and Inflation 29Operation 31Servicing Tire and Rim 31Inspection Procedures 31

4. Collecting and Storing Tire Information 34Branding Tires 35Radio Frequency Identification Tags 36RF Tag Usage 36

5. Inflation 37Underinflation 40Do’s and Don’ts for Maintaining Proper

Inflation Pressure 42Nitrogen Inflation 42

6. Total Vehicle Alignment 43Steer Axle Alignment 45Loaded vs. Unloaded Alignment Settings 45Toe 46Camber 46Caster 46Ackerman Steering Effect on Tire Wear 47Drive Axle Alignment 48Trailer Axle Alignment 49In-Service Alignment Recommendations 49

7. Factors Affecting Treadwear 50Steer Tire Wear 52Setback Steer Axles 53Drive Tires 54Bearing Adjustment 55Environmental Effects 56How Speed Affects Tire Wear 57

Section Title Page8. Ride Disturbance 58

Ride Test Tips 60Ride Diagnostics: Tires/Wheels 60Balance Related Vibration 60Run-Out Related Vibration 60Mesuring Radial Run-Out 61

9. Factors Affecting Truck Fuel Economy 63Vehicle and Engine Design 64Vehicle Operation 67Tire Selection and Maintenance 70Environmental Conditions 74Tire Description & Specifications 76Summary 77Appendix 78

10. Tire Repairs 80Nail Hole Repair Procedures 82Section Repair Limits in

Sidewall and Shoulder Area 84Application of Center-Over-Injury

Section Repairs 85Radial Ply Tires 85Crown Repair Limits 85

11. Retreading 86Introduction 87Planning A Retread Plant Visit 87Plant Inspection 87Definitions 90Retread Plant Inspection Checklist 92

12. Miscellaneous 94Use of Chains on Radial Truck Tires 95Tire Siping 95Dynamometer Tests 96Mixing Radial and Bias Ply Tires 96Noise 97Tire Storage Recommendations 99When Does The Warranty End? 100Tire Sealants And Balance Materials 100

13. Standards and Regulations 101Federal Motor Vehicle Safety Standards

Testing and Certification 102Federal Motor Carrier Safety Regulations 102Inspection 103Minimum Tread Depths 104Commercial Vehicle Safety Alliance (CVSA) 104Regrooving/Tire Siping 105

Load Ratings and Inflation Data 107Truck Type and Weight Class 108Index 109

CONTENTS

ForwardThis manual was prepared as a

guide to the selection, operation,

and maintenance of Goodyear

radial truck tires.

The subjects covered are all

essential to good tire performance.

Detailed explanations on selection,

mounting, air pressure, vehicle

alignment, and other important

issues are supported by illustrations

for clarity.

Use this manual often as a

reference. It will help you get

extended fuel economy, treadwear,

and casing life from your Goodyear

radial tires.

Radial

Truck Tire

Terms

S E C T I O N O N E

5

Radial Truck TireNomenclature

S E C T I O N O N E

6


Tire ComponentsA. Liner — A layer or layers of rubber in tubeless tires that resists air diffusion. The liner in the tubelesstire replaces the innertube of the tube-type tire.

B. Bead Core — Made of a continuoushigh-tensile wire wound to form a high-strength unit. The bead core is themajor structural element in the plane oftire rotation and maintains the requiredtire diameter on the rim.

C. Chafer — A layer of hard rubber thatresists rim chafing.

D. GG Ring — Used as reference forproper seating of bead area on rim.

E. Apexes — Rubber pieces with selected characteristics used to fill in the bead and lower sidewall area andprovide smooth transition from the stiff bead area to the flexible sidewall.

F. Sidewall — The sidewall rubber mustwithstand flexing and weathering andprovide protection for the ply.

G. Radial Ply — The radial ply, togetherwith the belt plies, withstands the loads of the tire under operating pressure. The plies must transmit all load, driving,braking and steering forces between thewheel and the tire tread.

H. Belts — Steel cord belt plies providestrength, stabilize the tread, and protectthe air chamber from punctures.

I. Tread — This rubber provides theinterface between the tire and the road.Its primary purpose is to provide tractionand wear.

Tire Areas1. Crown — Area of the tire that contacts the road surface.

2. Shoulder — Transition area betweenthe crown and tread skirt.

3. Tread Skirt — Intersection of treadand sidewall.

4. Sidewall — Area from top of bead tothe bottom of the tread skirt.

5. Stabilizer Ply — A ply laid over theradial ply turnup outside of the bead andunder the rubber chafer that reinforcesand stabilizes the bead-to-sidewall transition zone.

6. Bead Heel — Area of bead that contacts the rim flange, the “sealingpoint” of the tire/rim.

7. Bead Toe — The inner end of thebead area.

1.Crown

2.Shoulder

3. Tread Skirt

5. Stabilizer Ply

H. Belts

G. Radial Ply

F. Sidewall

E. Apexes

D. GG Ring

C. Chafer

B. Bead Core

A. Liner

6. Bead Heel

7. Bead Toe

4. Sidewall

ITread

UnisteelRadial

S E C T I O N O N E

7


• Aspect Ratio (AR) — The sectionheight divided by the section width,expressed as a percentage (SH/SW x 100 percent).

• Loaded Section (LS) — The width of the cross section at the Tire and Rim Association’s dual tire load and inflation pressure.

• Static Loaded Radius (SLR) — The distance from the road surface to the horizontal centerline of the wheel, under dual load.

• Minimum Dual Spacing — The minimum dimension recommended from rim centerline to rim centerline for optimum performance of a dualwheel installation.

• Net/Gross Ratio — Tread patterncontact area to total tread area.

• Outside Diameter (OD) — The unloaded diameter of the tire/rim combination.

• Section Width (SW) — The maximumwidth of the tire section, excluding anylettering or decoration.

• Section Height (SH) — The distancefrom the rim to the maximum height ofthe tire at the centerline.

Definition• Footprint — The surface of the tire incontact with the road surface at anygiven load and inflation pressure.

• Tread Width — Distance across tread surface.

• Non-Skid — Tread depth from treadsurface to bottom of major grooves.

• Undertread — Gauge of rubberbetween top of belt package and bottom of grooves.

• Turn Radius — Curvature of the tread face from shoulder to shoulder.

The Tire & RimAssociation Yearbook

The Tire & Rim AssociationYearbook provides essentialinformation for the interchangeability of tire,wheel and rim products forcars, trucks, buses, cycles,off-the-road, agricultural and industrial vehicles.

To obtain a copy, write or call:

The Tire & Rim Association, Inc.175 Montrose West Ave.

Suite 150Copley, OH 44321

330-666-8121www.us-tra.org

Section

Width (SW)

Static LoadedRadius (SLR)

FlangeHeight

Rim Width

OutsideDiameter

(OD)

Section Height (SH)

Minimum Dual Spacing

Loaded Section(LS)

Tire Selection

S E C T I O N T W O

Selecting the proper tire size, load range and

design is very important to insure satisfactory

performance. The best guide is to follow

past experience and use the advice of

professionals who are familiar with the types

of tires used in service conditions similar to

yours. Goodyear representatives are trained

to aid you in this important decision. The

following will provide basic guidelines for

proper tire selection.

*Information courtesy of The Maintenance Council (TMC)

— Recommended Practices Book

8

Tire Selection

S E C T I O N T W O

9

Tire Selection

PurposeThis Recommended Practice is

intended to make the tire purchaser, fleetoperator, or maintenance manager awareof major items for consideration, and toprovide a step-by-step thought processfor selecting the best type of tire for theapplication. The following sections provide a brief explanation of the varioustire selection criteria that must beaddressed. A summary of considerationsis also listed to enable the decision-makerto identify advantages and disadvantagesof each of the selection criterion.

If higher steer tire pressures arerequired, this may mean you’ll be usingdifferent inflation pressures for drive andtrailer tires.

While the considerations may not be all-encompassing, they point out themajor issues that should be dealt withbefore selecting a tire. Because of thepace of technology change in the tireindustry, certain considerations maybecome less important while new onesmay arise from time to time.

IntroductionThe process of determining which

tire to select for a particular job or operation may sometimes seem difficultor complex. Indeed, the proper selectioninvolves a myriad of decisions concerningthe size, the type, and the tread designof the tire based upon the intendedapplication. Other considerations are the manufacturer of the tire, the tiredealer, price, availability, and the warrantycoverage which comes with the product.However, there is a logical method forselecting which kind of tire would bemost appropriate depending upon anassessment of the many considerationssurrounding the fleet operation.

Be aware that all tire use selectionswill have advantages and disadvantagesdepending upon vehicle design andvocation. Make certain your choices arein line with your perceived fleet needsand contact your tire suppliers for expertassistance in making your selection.

Tire Clearance RestrictionsNew Equipment — When spec’ing anew vehicle, the prospective owner canbe quite imaginative in creating a vehiclethat meets specific needs. Tires, however,may be the limiting factor to this creativitysince they must be capable of carryingthe expected load and be made to certainminimum dimensions. The fleet ownercan choose from several types of tires thatcan carry the anticipated load, but maybe forced to redesign a vehicle’s overalldimensions if the tires that can carry theload are larger than originally desired.

Existing Equipment — When changingthe type or size of tires used on existingequipment, space restrictions are moreinflexible. Not only must a tire be selectedthat can carry the load, it must fit in anexisting space. In addition, when changingtire sizes on an existing power unit, consideration must be given to theeffects the new size tire will have on

the gear ratio. Some change may requirea different rim (width, pressure limits).

Tire Clearances — In order to select a new tire size for a given application,the dimensional clearance of the tiremust be acceptable. The followingdefine those areas that must be checked:

1. Vertical Clearance is the distancebetween the top of the tire tread and the vehicle immediately above it. This clearance varies as the axlesoperate. The vertical movements of the whole axle in relation to thechassis are normally limited by anaxle stop. To determine vertical clearance, subtract the axle stop clearance from the total clearanceabove the tire at rest.

2. Front Tire Clearances are the distancesbetween the front tires (on bothsteering lock positions) and the vehicle. Clearances of front wheelsmust be checked by turning the wheelsfrom full left lock to full right lock,since the minimum clearance mightoccur at some intermediate point.

3. Overall Width — When fitting largeror wider tires to an existing vehicle,the overall width across the dual tiresis increased by half of the increase inthe section width of each outside tireand the increase in offset of each outside wheel. The overall widthacross the tires is measured at thetwelve o’clock position and not at thelower side (six o’clock position)where the tires deflect due to load.

When using tire chains, a minimum of two inches more clearance is neededto provide clearance between the dual assembly.

TIRE SELECTIONPROCESS

S E C T I O N T W O

10

Tire Selection

Rims And WheelsThe selection of rims or disc wheels

goes hand-in-hand with the selection oftires. When ordering new equipment,specifying the recommended rim for thetire size selected will ensure optimumperformance.

Rims are identified by a diameter andwidth and, in the case of tube-type rims,also with a type code. The type codedesignations are used on tube-type products to help identify rings and rimsfor interchangeability. For example, a 20 x 7.5 FL rim would have a nominal diameter of 20 inches; a width betweenthe flanges of approximately 7.5 inches;and be a FL type rim. Other typical type codes are: CR, 5˚, LB, and LW. It isimportant that the rim size be approvedfor the tire being used. This assures properfit and performance of the tire and rim.The tire or rim/wheel manufacturer’s databook or Tire & Rim Association Yearbook (orequivalent), and www.goodyear.com/truckspecify approved rims for each tire size.

When selecting the correct wheel orrim type, it is important to determine theoperating conditions to which the wheelor rim will be subjected. Conditions toconsider are loads, speeds, road surfaces,use of bias or radial tires, tire pressure,tire size, and the use of tube-type ortubeless tires.

Caution is necessary in selectingwheel/rim offsets to ensure proper tirespacing, body and chassis clearance, andoverall track width. If dual tires are used,dual spacing and tire clearance must be considered.

Take precautions to ensure that therim and wheel not only have the approvedcontour, but also have the load and inflation ratings sufficient for the tire inthe intended application.

For more detail in selecting the correct wheel/rim, refer to TMC RP211A, Rim and Wheel Selection and Maintenance.

Radial and Bias TireConstruction

There are two basic types of tire construction — radial and bias — thatmust be considered when choosing eithera replacement tire for certain applicationsor when spec’ing new tires on an originalequipment vehicle Figure 2.1.

Bias ply tires are constructed of overlapping crossed layers of cord material and are typically made withnylon, polyester, or other materials. The crossed plies run on a diagonal fromtire bead to tire bead and comprise agenerally stiff sidewall area. Sometimes,extra crossed plies or breakers are usedunder the tread area to further stiffen the crown area and provide better wear resistance or other performance parameters (such as puncture resistance, etc.).

Radial ply tires are made with thecord material running in a radial ordirect line from bead (at 90 degrees to the centerline of the tire), and are

typically made with one steel body ply or multiple body plies of other materials. Under the tread area, the radial tire usually has three or fourcrossed plies or belts made of steel cordto stabilize the crown area and offer better puncture resistance. The radialsidewall area is generally less stiff thanthe bias ply sidewall, though the treadarea is normally much stiffer.

Bias ply tires have been designed overthe years to perform in many differenttypes of applications from all-highway to on-off road, to all off-road serviceconditions. With the advent of the radialtire and some of its inherent advantages,the bias tire is now used much less frequently in long haul over-the-roadapplications. Radial tires typically areused in applications where heat build-upwith bias ply tires is a problem. With the many improvements to radial tireconstruction made in recent years, theradial tire is now used in virtually alltypes of service conditions.

Figure 2.1

Radial Bias

S E C T I O N T W O

11

Tire Selection

Bias Ply Tire Considerations• stiffer sidewalls give better driver

handling/feel• lower susceptibility to sidewall

snags/hazards/rusting• lower initial tire purchase price

Radial Tire Considerations• better treadwear performance• higher potential for retreading• more fuel efficient• lower susceptibility to tread

punctures• better traction characteristics

Tubeless And Tube-Type Tires

The tubeless tire is similar in construction to a tube-type tire, exceptthat a thin layer of air and moisture-resistant rubber is used on the inside ofthe tubeless tire from bead to bead toobtain an internal seal of the casing. Thiseliminates the need for a tube and flap.The two types of tires require differentrim configurations: the tubeless tire usesa single-piece wheel; and the tube-typetire requires a multi-piece wheel assemblyFigure 2.2. Both tires, in equivalent sizes,can carry the same load at the sameinflation pressure. However, tubeless tires generally offer more benefits thantube-type tires in line-haul operations.

Tubeless Tire Characteristics vs. Tube-type:• less complicated mounting process due

to use of a single-piece wheel• decreased weight with lighter tire/

wheel assembly• less maintenance of parts and reduced

parts inventory• improved bead durability potential

from less brake drum heat resultingfrom higher wheel clearance

• improved crown and sidewall durabilitypotential from cooler running tubeless casing

• better lateral stability from lower section height

• reduced downtime from punctures

Low Profile TiresLow aspect ratio tires are a category

of radial tubeless tires which feature section widths wider than their sectionheight. The ratio of tire section heightto section width for these low aspectratio tires generally fall between 80% to 70%.

Low aspect ratio tires have shortersidewall heights and wider tread widthsthan their “conventional” aspect ratio tire counterparts.

These differences lead to the following tire characteristics:• improved treadwear (less irregular

wear) on steer and trail axles• lighter weight and less federal excise tax• better trailer cube potential due to

smaller tire diameter on new equipment• improved stability and handling from

higher lateral spring rate• greater susceptibility to sidewall

curb damageAs fleet experience with low profile

tires increases, other considerations(such as vehicle geometry, alignmentmaintenance, and brake wear) may need to be addressed depending on theapplications and service requirements of the operation.

Drivetrain/gearing must be taken intoaccount when converting to low profiletires, either at the original equipment orreplacement level. These involve engineRPM, transmission, drive axle gear ratio,and tire RPM. The objective is to obtainthe most fuel efficient engine RPM/ground speed relationship consistentwith service condition requirements.

The effect on road speed at the sameengine RPM using a 55 mph base dependsupon which conventional aspect ratioand low profile tires are involved.Generally, if the percent change in thetire RPM is 3% or less, a gearing changeis not required Table 1.

Wide-Base (Super Single) Tires

A wide-base tire is simply a larger tirewith a lower profile by nature. Currently,the primary application in North Americais on vehicles whose front axle loads exceedthe capacity of standard tires. Constructionvehicles such as cement mixers and refusehaulers are prime examples. In additionto increased load capacity, these largertires provide improved flotation versusconventional size tires.

The common wide-base sizes include:385/65R22.5, 425/65R22.5, 445/65R22.5,435/50R22.5, and 445/50R22.5.

Table 1

TABLE 1

Conventional vs. Low Profile Tire Comparison

Diameter 41.5'' 40.0''Section Width 11.0'' 11.2''Nonskid 19/32'' 18/32''Rim 8.25'' 8.25''SLR 19.4'' 18.7''RPM 501 514

11R22.5 295/75R22.5(Low Profile)

S E C T I O N T W O

12

Tire Selection

The pros and cons of wide base singles versus duals in many performancecategories are dependent on specificvehicle configuration and operations.Some key considerations and potentialbenefits are discussed in the followingparagraphs.

Potential advantages for wide basesingles include: increased payloadweight and volume due to lower tire/wheel weight/volume, ease of maintenance(no mismatched tires, etc.), reducedinventory, improved fuel economy, andsometimes more uniform wear in free-rolling trailer applications. Possible legal restrictions of nonsteer axle application of wide base singles shouldbe thoroughly investigated before finalizing size selection.

Original equipment fitment of widebase singles offers the potential for lowering the center-of-gravity and thusimproving the stability of vehicles suchas tankers. In retrofit applications, caremust be taken to properly select wheel/rimoffsets to maintain a tracking width foracceptable stability. A common way to

take full advantage of the wide base single concept is to use a 77.5 inch wideaxle in place of the standard 71.5 inch.

Inherent advantages of duals versuswide base singles include standardizationof tires/wheels, reduced road service dueto tire problems through “limp” capabilityto get to repair facility, and improvedvehicle stability/control during tire air loss.

Matching Tires For Speed And Axle Weights

As mentioned earlier, there are drivetrain/gearing considerations which mustbe made at the original equipment orreplacement level when utilizing lowprofile tires. These involve engine RPM,transmission, drive axle gear ratio andtire RPM. The objective is to obtain themost fuel efficient engine RPM/groundspeed relationship consistent with service condition requirements.

The effect on road speed at the same engine RPM, using a 55 mph base,depends upon which conventional sizesand which low profile diameters areinvolved. Generally, if the percent

change in the tire RPM is 3 percent orless, a gearing change is not required.

In a tire selection process, it ismandatory that consideration be givento selecting a tire size and load rangewhich at least equals the maximum loadrequirements by axle position (steer,drive, or trailer). All highway truck tireshave load limits established for tires usedin normal highway service. Therefore,when selecting a tire for service, boththe carrying capacity and speed implications must be considered.

For example, when selecting tires for a tractor-trailer combination with a gross combination weight (GCW) of 80,000 lbs. and an axle weight distribution of 12,000 lbs. on the steer,34,000 lbs. on the tandem drive, and34,000 lbs. on the tandem trailer axles,common conventional tire sizes used are 295/75R22.5 (275/80R22.5),285/75R24.5 (275/80R24.5), 11R22.5and 11R24.5 Load Range G. The load and inflation tables (from theEngineering Data Book for Over-the-Road Truck Tires or www.goodyear.com/truck) for these sizes are shown in Table 2.

11R22.5 Dual 4380 4580 4760 4950 5205(F) 5415 5625 5840(G) 5895Single 4530 4770 4990 5220 5510(F) 5730 5950 6175(G) 6320

11R24.5 Dual 4660 4870 5070 5260 5510(F) 5675 5840 6005(G) 6205Single 4820 5070 5310 5550 5840(F) 6095 6350 6610(G) 6790

295/75R22.5 Dual 4500 4690 4885 5070(F) 5260 5440 5675(G) 5800 6005(H)Single 4500 4725 4945 5155 5370 5510(F) 5780 5980 6175(G)

285/75R24.5 Dual 4540 4740 4930 5205(F) 5310 5495 5675(G) 5860 6175(H)Single 4545 4770 4990 5210 5420 5675(F) 5835 6040 6175(G)

(F) = Load Range F (G) = Load Range G (H) = Load Range H

Table 2

TABLE 2Tire Load Limits (lbs.) At Various Cold Inflation Pressures

(The Pressure is Minimum for the Load, Maximum Speed of 60 MPH)

Inflation Pressure (psi)Size Usage 70 75 80 85 90 95 100 105 110

S E C T I O N T W O

13

Tire Selection

Therefore, with conventional tiresizes, it would require at least an 11R22.5tire with a carrying capacity of 6,175 lbs.at 105 psi on the steer axle (which wouldbe the most critical for load and singleapplication).The 11R22.5 would be morethan adequate for drive and trailer axleapplications. In low profile sizes, the285/75R24.5 at 105 psi would have theadequate carrying capacity for the steeras well as the drive and trailer axle loads.

The Tire and Rim Association hasestablished inflation pressures for loadlimits at various speeds for truck tiresused on improved surfaces. Consult the Tire and Rim Association table orindividual tire manufacturer for specificrecommendations to meet your operating condition. You can contactThe Tire and Rim Association at 330-666-8121 or www.us-tra.org.

Tread Design SelectionThe selection of the proper tread

design for an intended application isvery important to the fleet that wishes to obtain the maximum potential fromtires and thereby lower tire expenses.Selection of the proper tread design

is not an exact science, but there are certain general rules and guidelineswhich, if followed, can lead to selectinga tread design that will give the maximumdesired performance for the serviceapplication in a particular fleet. In orderto help select the right tread design, referto Technology & Maintenace Council RP(Recommended Practice) 220, Tire TreadDesign Selection.

Fleet OperationConsiderations

When evaluating the many tireoptions available for any given vehicleapplication, there are numerous management considerations in additionto the mechanical considerations alreadycovered. While these considerationsapply most directly when spec’ing outnew equipment, they also can be used to reevaluate tire selection prior to tire replacement.

Fleet Operation Considerations• availability of various products and

service maintenance• tire purchase price vs. performance

(cost-per-mile)• financial inventory investment and

space requirements

• maintenance training for personnel• retreadability/repairability costs

and servicing• warranty and adjustment servicing• leading edge or “experimental”

product availability• effects of non-standardization• effects of tire down-sizing on vehicle

gearing and braking• timing for phase-in or changeover

programs• legal or contractual requirements

Retreadable TiresRetreading your worn tires or

purchasing retreads from a dealer canprovide new tire service and performanceat a fraction of the cost of a new tire.When selecting new tires, purchasethose that are designed to be retreadable.To insure retreadability, follow prescribedmaintenance and avoid regroovingwhich may damage the valuable casing.

Retreaded Tire Considerations• provide equivalent service and

performance• reduce overall cost-per-mile• conserve natural resources• tread designs available for all

applicationsFigure 2.2: Tire Construction

Tube-Type Tire Tubeless Tire

Tube

One-PieceRim

Flap

MultipieceRim Rim Diameter Difference — 2-1/2 inches

S E C T I O N T W O

14

Tire Selection

Figure 2.3: Overall Width, Dual Tires

Figure 2.4: Aspect Ratio

Tire Section Width

Common aspect ratio categories of medium truck tires are as follows:-98 Tube-type conventional sizes (10.00R20)-88 Drop center tubeless (11R22.5)-70-75-80 Low profile (295/75R22.5, 255/70R22.5)-65 Wide-base singles (18R22.5, 445/65R22.5)

Tire Section Width

Wheel Offset

Overall Diameter

Rim Width

Section Width

Overall Width

“Aspect Ratio” is defined as the percent of the section height to the section width of the tire.

Section Height

New Tire Dimensions

Dual (or Center-to-Center Spacing)

Wheel Offset

Vehicle Clearance

(V/C)

Tire

Cle

aran

ce

Section Height

Section Width= .75 Aspect Ratio

Overall Assembly Width

S E C T I O N T W O

15

Tire Selection

Figure 2.5: Sizing Definition *Information courtesy of The Maintenance Council (TMC) — Recommended Practices Book

Standard Aspect Tires Low Profile Tires

More recently the trend has been towards low profile tires. These are usually tubeless tires designed for either 22.5 or 24.5'' diameter wheels. The most common low profile tires are listed below showing conventional sizes which they normally replace:

Width

Height is 75% of Width

Standard Aspect

Radial Tire 90-series(11R22.5)

Low ProfileRadial Tire 75-series

(295/75R22.5)

Low Profile Sizes295/75R22.5 (275/80R22.5)285/75R24.5 (275/80R24.5)

Conventional Sizes10.00R20, 11R22.510.00R22, 11R24.5

11 R 22.5

Rim diameter in inches(15'' tapered bead)

Radial

Cross Section (inches)

295 / 75 R 22.5

Rim diameter in inches

Radial

Cross Section (mm)

Aspect Ratio

S E C T I O N T W O

16

Tire Selection

TIRE SELECTIONPROCESS WORK SHEETSTEP 1Record maximum axle weights expected during vehicle operation.

Axle WeightsSteer Drive Drive/Trail Trail Trail

STEP 2Check types of service

___________ Line Haul —Travel on interstate and normal highway roads at maximum speeds with runs over 250 miles.

___________ Local — Most travel between and around city areas, with runs generally less than 250 miles.

___________ On-Off-Road — Travel on some highway and secondary roads with possible travel on gravel/dirt roads.

___________ Off-Road — Travel on mostly secondary and gravel/dirt roads with a potential for tread cutting due to rocks, debris, etc.

STEP 3Determine size restrictions

1. If spec’ing for new equipment, provide for adequate tire clearance and brake compatibility.

a. Minimum tire diameter due to brake restrictions _________________________

b. Maximum tire diameter desired _________________________

2. If retrofitting tires on existing equipment, will rim size change?

a. [ ] No (State Rim Size) _________________________

b. [ ] Yes (Select new rim size in Step 10)

If wheel size becomes larger (change from dual tires to wide-base tires or to larger dual tires), determine present tire clearances:

(1) Vertical Tire Clearance _________________________

(2) Front Wheel Clearance _________________________

(3) Overall Width of Present Tire _________________________

(4) Overall Diameter of Present Tire _________________________

(5) Current Wheel Offset _________________________

(6) Overall Width Across the Tires _________________________

STEP 4Write in type of tires to be used — Duals or Wide-Base _________________________

STEP 5Write in type of construction to be used — Radial or Bias _________________________

S E C T I O N T W O

17

Tire Selection

STEP 6Write in type of air retention construction — Tube-type or _________________________Tubeless (This will be determined by the type of rims tobe used.)

STEP 7Write in aspect ratio to be used _________________________(This step may be incorporated into Step 8.)

STEP 8Select tire size from Tire and Rim Association tables or tire manufacturers’ data books using the tire described in Steps 4 through 7.Do this by cross checking the axle weights and speed restrictions to be sure the tires can carry the maximum axle load recorded inStep 1 at operational speeds.

Tire Size ____________________ Dual Load _______________ Single Load _______________ at ____________ psi

If maximum loads cannot be attained with the initial tire desired, a change in either Steps 3(1), 4, or 5 must be made. Repeat Step 8 until a tire size with the necessary carrying capacity is selected.

STEP 9Write in selected tire’s dimensions from Tire and Rim Association tables or tire manufacturers’ data books.

Overall Diameter _________________________

Overall Width _________________________

Revolutions per Mile _________________________

1. If spec’ing new equipment, redesign space restrictions if adequate clearance and brake compatibility are not afforded, or return to Step 8 and select another size tire.

2. If retrofitting tires on existing equipment and larger size tires than presently used are selected, determine clearances:

a. Vertical Clearances:

Vertical Tire Clearance of Present Tire _________________________

Overall Diameter of Present Tire + _________________________

= _________________________ (Subtotal)

Overall Diameter of Selected Tire - _________________________

Vertical Tire Clearance = _________________________(Consult the vehicle or suspensionmanufacturer for minimum clearancerequired.)

Overall Vehicle Height _________________________

S E C T I O N T W O

18

Tire Selection

b. Front Tire Clearance:

Clearance of Present Tire _________________________

Overall Diameter of Present Tire + _________________________

= _________________________ (Subtotal)

Overall Diameter of Selected Tire - _________________________

Front Tire Clearance = _________________________(Must be a positive number.)

c. Overall Width:

Overall Width Across the Present Tire _________________________

Overall Width of one current - _________________________outside tire

= _________________________ (Subtotal)

Overall Width of one selected + _________________________outside tire

= _________________________ (Subtotal)

Offset of both current outside wheels - _________________________

= _________________________ (Subtotal)

Offset of both selected outside wheels + _________________________

Overall Width (Must be 102'' or less.) _________________________

If all clearances are not suitable, return to Step 8 and select a smaller size tire.

STEP 10Select wheel/rim from Tire and Rim Association tables or wheel/rim manufacturers’ catalogs. Check to see that load and inflationpressure ratings are adequate (compare with Single Load and Pressure in Step 8).

Wheel Size ____________________ Load Rating _______________ at __________ psi

STEP 11Select tread designs for steer, drive, and trailer positions using Technology & Maintenance Council Recommended Practice 220, Tire Tread Design Selection. Call 800-ATA-Line to order.

STEP 12Incorporate fleet operation considerations at this point. Compute gear ratio changes if appropriate.

Mounting

Procedure

S E C T I O N T H R E E

It is essential that good mounting procedures

be followed in order to obtain optimum tire

performance and operating efficiency. Also,

tire and rim servicing can be dangerous.

To prevent serious injury, be sure you

know, understand and follow all procedures

and safety instructions.

19

Mounting Procedure


20

Mounting Procedure

SAFETY INSTRUCTIONS LUBRICATIONDo not mount or demount tires

without proper training. Wall chartscontaining mounting and demountinginstructions for all on-highway rimsshould be available through your normalrim supplier. “Safety Precautions forMounting and Demounting Tube TypeTruck/Bus Tires” are also availablethrough the United States Departmentof Transportation, National HighwayTraffic Safety Administration,Washington, DC 20590.www.nhtsa.dot.gov

WHEEL INSPECTIONGUIDELINES

Remove any and all cracked wheelsfrom service.

Cracked wheels not removed fromservice will fail.

A non-water base commercial beadlubricant should be used since water inthe tire can cause excessive rim corrosionproblems. However, thin vegetable oilsoap solutions with a water base areapproved. Lubricants which contain arust inhibitor can be an advantage. Avoidthe use of excessive lubricant Figure 3.1.

Never use anti-freeze, silicones, or petroleum based lubricants.

When a tube and flap are not properlylubricated before mounting, they will be stretched thin in the tire bead andrim region Figure 3.2. This will causepremature failure.

Inspect wheels for sometimes small cracks emanatingfrom stud holes.

These cracks will continue to grow outward, throughthe “dish” or between stud holes.

Inspect wheel mating surfaces for chaffing, corrosion or pitting.

Mating surfaces should be clean, smooth, and flush so as to permit uniform distribution of clamping andtorquing forces.

Remove wheels from service with excessively worn mating surfaces and/or worn or “wallowed” stud holes.

Figure 3.1 Lubricate areas shown by arrows

Figure 3.2 Area of tube stretched thin due to improperlubrication and mounting.


21

Mounting Procedure

Always use lubricant when mountingradial truck tires to ensure proper bead seating and to prevent eccentricmounting. The more flexible sidewall ofthe radial tire makes the use of lubricantin the bead area more critical than forbias ply tires which have stiffer sidewalls.If the bead is not properly seated oneither a 2-piece or 3-piece rim andbecomes “hung-up,” usually on theremovable flange side of tube type tires,the lower sidewall area flexes excessivelyunder load, and irregular treadwear andcracking in the lower sidewall bead areaoften result. Improperly seated beadscan also produce severe truck vibrationand cause chafing through the lowersidewall down to the wire.

When the bead is not properly seated,the bead toe is lifted, and the flap maybe forced under the toe Figure 3.3.Continued up and down flexing of thetoe can cut through the flap. As thisprocess continues, the tube becomespinched and may fail suddenly.

TIRE & RIM CLEANINGTo prepare the tire, first clean and

dry the inside with an air hose. Inspectfor loose material inside. A small pieceof paper left inside a tube type tire canchafe a hole in the tube and cause a flat.Dust the inside of the tire sparingly withdry soapstone to prevent the tube fromsticking to the tire. Do not let soapstone accumulate in the tire.

Also inspect and clean the tire beadsto remove any accumulation of corrosionmaterial or rubber that may be stuck toit. Wipe the beads with a dry cloth until clean.

Clean rims to remove dirt, surfacerust, scale and rubber build up. Repaintto stop the detrimental effects of corrosion and facilitate checking andtire mounting. Be sure to clean the tireseat areas thoroughly to insure properfitment of the tire and to eliminate the potential for air leaks in tubelessassemblies. Also file or use emery cloth

to remove any burrs or nicks on the tireside of the rim. These may damage thetire during mounting or in service. Bevery careful to clean all dirt and rustfrom the lock ring and gutter. This isimportant to secure the lock ring in itsproper position. A filter on the air inflation equipment to remove moisturefrom the air line helps to prevent corrosion. Drain the air tank frequently.The filter should be checked periodicallyto see that it is working properly.

Check rim components periodicallyfor cracks. Replace all cracked, badlyworn, damaged and severely rustedcomponents with new parts of correctsize and type. When in doubt replace.Mark or tag the unusable parts as scrapand remove them from the service area.

Do not, under any circumstances,attempt to rework, weld, heat, or brazeany rim components that are cracked,broken, or damaged. Replace them withnew parts or parts that are not cracked,broken, or damaged and which are ofthe correct size and type.

Make sure matching parts are beingassembled. Check DOT chart, your distributor or the manufacturer if youhave any doubts.

Figure 3.3 Improper bead seating

GG Ring

GG Ring

PossibleFlap andTube Pinch

Area ofExcessiveFlexure

BeadProperlySeated Bead Not

ProperlySeated


22

Mounting Procedure

ASSEMBLY OFTIRE TUBE FLAPTUBES & FLAPS

Always install a new radial tube and anew radial flap in a new tire. Use onlytubes designated for radials and makesure the proper size tube and flap is used.Never use undersized tubes. Certain precautions must be taken when mountingused flaps, or damage to the tire andtube will result.

New truck and bus flaps can be usedwith any one of several different tire andrim sizes as recommended. But, onceused, the flap must be remounted in thesame size tire and on the same size rimfrom which it was removed. Always usea flap of adequate width to prevent tube pinching.

As a precaution against flap failure,mark the tire and rim size on the flap atthe time of removal (if inspection showsthat it is not damaged and can be usedagain). When the flap is again mounted,this marking protects against the dangerof misusing the flap with the wrong sizetire and rim.

The valve core provides a temporaryair seal while air pressure checks arebeing made, but it will leak air slowly ifthe cap is loose, missing, or damaged.Use a sealing-type valve cap. A metalcap is preferred but a sealing-type nyloncap is acceptable.

In the case of used tires and tubes,recondition the valve stem every time atire is mounted. Recondition the threadson both the inside and the outside ofthe stem with a valve stem rethreadertool. Install only new valve cores. Usedor dirty valve cores may be defective.Don’t take a chance. Valve cores mustbe stocked in clean closed containers atall times, since a small particle of dirtwill render a core ineffective.

Insert the tube into the tire and partially inflate it to round out the tube.Apply rubber lubricant to the inside andoutside surfaces of both beads and tothe portion of the tube that appearsbetween the beads. Do not allow lubricant to run down into the tire.Apply the lubricant with a cloth, swab, or brush.

For detailed, illustrated instructionson procedures and proper use of tiretools in mounting and demountingGoodyear radial truck tires on varioustypes of rims, see the wall charts available through RMA (www.rma.org).

After mounting and before inflatingthe tire, inspect all components of multipiece rims to make sure they are inplace. See that tires are properly mountedand seated on the rims by checking thedistance between the tire GG ring andthe rim flange. This distance should bethe same all the way around the tire;that is, the rim flange must be concentricwith the GG ring (refer to the photographFigure 3.4 below, and Figure 3.3 onpage 19, for GG ring location on tire)and the distance must be the same forboth sides.

Tube type tires should always beaired once before the valve core isinstalled. This will eliminate confusionin inflating a tire twice. All tube typeradial tires should be inflated twice.

To inflate twice, the tire is inflated to full inflation pressure, then all the air is let out and the tire is reinflated.The first inflation seats the bead of thetire, but over stretches the tube and flap in the area between the bead toes.Completely deflating the tire allows thetube and flap to relax. A partial deflationdoesn’t get the job done. The full deflation and reinflation stretches the tube and flap uniformly.

Important: During the first inflation,the airing should be stopped at about 10psi, and the side ring or lock ring shouldbe checked carefully to make sure it isproperly seated. Also, it is recommendedthat the side ring or lock ring seating be checked at 10 psi during the second inflation.

Install a sealing-type valve cap fingertight. A valve cap has two functions toperform. The first is to keep dirt fromdamaging the valve core sealing surface.The second, is to provide an air seal for

CAUTIONUsed flaps cause tube failure unlessmounted with the size tire and rimoriginally used.

Figure 3.4 Use of GG ring to indicate correct mounting

WARNINGAlways use a safety cage orapproved safety device and extension hose with air gauge and clip-on air chuck for airing a tire on a multi-piece rim or single piece rim.

WARNINGNever, under any circumstances, attempt to seat rim components by tapping with mallet when tire is inflated or partially inflated. Deflate tire first.


23

Mounting Procedure

the valve. A valve cap, therefore, mustbe durable.

The black plastic cap that sometimescomes on a new tube is not a valve capand will leak air at the high inflationsused in truck tires. Its purpose is to keepdust and dirt out of the stem duringshipment, protect the threads of thestem, and shield the folded tube againstabrasion by the threads. The plastic capthreads are easily stripped; the plasticcap will crack in cold weather and willmelt if the stem comes in contact withthe brake drum. A metal valve cap contains a rubber gasket which providesan air seal; a plastic cap contains none.Therefore, always use a metal cap or aself-sealing nylon cap.

Valve extensions, or “air-through”valves are not a substitute for caps, sincethey are still subject to core seal leaks athigh pressure. Valve extensions require asealing-type valve cap.

Bend the valve stem to its properposition. If it is left flat and touching the rim, the valve cap will be difficult toremove and accurate air pressure checkswill be hindered. (If it is easy to checkthe pressure in a tire, it is more likely tobe checked.) The stem should not bebent up enough to cause it to touch thebrake drum. Heat from the drum will beconducted along the brass valve stem tothe tube/flap area around the stem baseand cause decomposition of the rubber.This will lead to eventual tube failure. In such a heated valve stem, the valvecore seal may also be ruined.

After the tire is mounted and inflated,the tire/wheel assembly should be putinto stock for 24 hours to permit a testof its air retention. Just prior to beingput in service, the pressure in the tireshould be checked and compared withthe initial value applied. If the pressureis more than 5 psi lower, the tire shouldbe withheld from service and checkedfor a leak.

For mounting tubeless tires, the procedure is about the same as for tubetype tires except that it is not necessaryto inflate twice. Cleaning the rim isagain critical because the tire dependson the rim for its air seal. Make sure theinside of the tire is clean and dry. If tireshave been stored outdoors, any water inthe tire must be removed and the tiredried before mounting. Water vapor inthe inflation air tends to cause rim corrosion. The valve stem must beinspected to make sure it is tight in therim and that the rubber grommetbetween the rim and stem is in goodcondition.

To install the tubeless tire on the rim,lubricate both bead seats of the rim andboth tire beads to ensure damage-freeand uniform mounting. Bead lubricantmust also be used during demounting toavoid damage to the bead area. Due totheir greater sidewall flexibility, it maybe necessary to use an inflation aid tohelp seat radial tubeless tire beads. Fordetailed mounting and demountinginstructions, refer to the wall chartsavailable through OSHA OccupationalSafeaty and Health Administration(www.osha.gov). When using tire irons,exercise caution to prevent damage tothe tire or rim.

Check that the distance between the tire GG ring and the top of the rim or wheel flange is uniform allaround the tire, and that the distance is the same on both sides of the tire. If this distance is not uniform, the bead is not properly seated.

If the GG ring in no concentric withthe rim flange, it is recommended thatthe “inflate-twice” procedure also beused in mounting tubeless tires in orderto seat beads properly.

INSTALLATIONInstallation of the tire on the vehicle

is the final step. When pulling a tirefrom stock, check the air pressure againstthe desired value. When tires are to bemounted as duals, make sure that thetwo tires are actually the same size. (See Matching of Duals on page 25.)

Measure the outside diameter ofevery tire after it is mounted and inflatedand before it goes into stock. The diameter should be written on the treadso that it is visible when the tire is inthe spares rack. Then by simply lookingat the treads of the spares in stock, areplacement tire of the correct diameterto match an already mounted dual canbe selected.

There are many ways of measuringthe size of a tire, but two ways appear to be more satisfactory than the others.Both involve measuring the completecircumference of the tire. The first usesa 14-foot endless steel mating tape. This is a steel band that is formed into ahoop. The hoop is slipped over the tire,pulled up tight, and a reading made.The second type is a pocket-size steeltape. With this it is necessary to hookthe end in the tread and roll the tire onerevolution, which brings the tape endback around and permits a reading ofthe circumference.

Another way of measuring tires uses calipers that measure tire diameter.The tape method is preferred because it provides an average diameter ratherthan any one particular diameter measurement.

TUBELESS TIREMOUNTING

WARNINGAlways use a securely held safetycage and extension hose with clip on air chuck for airing thetire. Rapid air loss can propel the assembly.


24

Mounting Procedure

On demountable rims, lugs should be tightened uniformly in a triangulatedor criss-cross sequence to achieve trueness of the rim on the wheel. Lugnuts should be torqued properly so theydo not loosen in use. On disc wheels,stud nuts should also be drawn up andtightened in a criss-cross sequence. See rim and wheel manuals for moreinstallation details. Lug or stud nutsshould be checked for tightness after the first 100 miles of travel and onceeach week thereafter.

DEMOUNTINGAlways deflate any tire to be removed

prior to loosening rim or wheel nuts.Bead lubricant must be used whendemounting tubeless tires.

Figure 3.5 Measuring with pocket size steel tape.

Figure 3.6 Proper sequence for tightening stud nuts onan 8 stud system.

Figure 3.7 Proper sequence for tightening stud nuts onan 5 and 6 stud systems.

Figure 3.8 Proper sequence for tightening stud nuts on10 stud system.

1

3

2

8

4

1

4

2

1

6

4 5

3

2

110

3

5

72 9

4

6

8

5

3

6

7

5


25

Mounting Procedure

Mismatched duals have the same effecton the life of tires as low inflation oroverload. An underinflated tire on a dualassembly shifts its share of the load to its mate, which then becomes overloadedand frequently fails prematurely. A difference of 15 psi inflation may resultin the lesser inflated tire supporting 500pounds less than the tire with the properinflation. A similar action occurs whenone tire’s diameter is smaller than itsmate. A difference of 1/4 inch in diametermay result in the larger tire carrying 600pounds more than the smaller. The shiftin load becomes more prevalent as thedifference in diameters or inflationbecomes greater.

Improperly matched duals are subjectto rapid treadwear because the larger tire carries more load and will wear fast .Although the mismatched duals have different diameters, they must rotate atthe same speed. The smaller tire thenalso wears unevenly because it is forcedto scuff over the road. The overall resultis abnormal and unequal treadwear forboth tires.

Improperly matched duals may alsolead to sudden air loss as a result of onetire being required to flex severely indoing more than its share of the work.

In addition to matching diameters andinflation pressures on dual installations,it is very important not to mix radialsand bias ply tires on the same axle dueto different load/deflection characteristicsof these two types of tires. Radial tiresdeflect more under a given load thanbias ply tires. If radial and bias ply tiresare mixed in dual installations on thesame axle, the bias ply tires will bear the greater part of the axle load and may operate in an overloaded conditionthat will lead to reduced mileage andearly failure.

Radial tire overall diameter will governthe revolutions per mile obtained from a given tire. It is necessary to closelymatch tire revolutions per mile with tandem drive axle units coupled directlytogether, as when an interaxle differentialdoes not exist or is locked out. Otherwise,the drive transmission may freeze up orfail in some way, and/or excessive slipon one of the sets of tires will lead to aloss in traction and uneven wear.

It is important that the tires of tandemdriving axles be inspected and matchedat regular periods, as determined by thetype of service.

Matching dual tires is important to insure even wear and load sharing capabilities. Tire circumference of dualsshould be as close as possible with amaximum tire circumference toleranceof 3/4" for tire sizes 8.25R20 and 1-1/2"maximum circumference tolerance fortire sizes 9.00R20 and larger.

When mounting duals on a truck,there will generally be some differencein the diameter of the two tires (withinthe limits described above). Mount thesmall tire on the inside. The outside tirewears faster than the inside tire. As itwears its diameter will approach that ofthe inside tire. Additionally, any crownon the road will favor the placement ofthe smaller diameter tire on the inside.

At the time of mounting duals on avehicle, locate the two valves diametricallyopposite (180 degrees apart) for accessibility. Hand holes on disc wheelsmust be located so that the inside valveis accessible.

MATCHING OF DUALS


26

Mounting Procedure

Proper spacing between dual tires is important. Too often, the service rendered by dual tires is sharply reducedbecause of insufficient spacing. It is acondition caused by either (a) oversizedtires or (b) improper rims and wheels.Tires mounted too close together do notallow proper air circulation to dissipatetire heat. Heat increases tire tread lossrate and reduces tire durability. When atruck is heavily overloaded, insufficientspacing can cause the sidewalls of theduals to rub together, wear off rubber,and become overheated due to continuous friction.

If the space between duals is toogreat, there will be excessive draggingand scuffing of the outside tire each time a turn is made. Also, check overallvehicle track width to assure compliancewith width laws.

Note that proper dual spacing forradial tires is the same as for bias ply.

An understanding of the geometry of a dual tire installation is important. A cross-section through a typical dualinstallation is shown in Figure 3.9. The dual spacing of the installation isthe sum of the rim offsets and the spacer width.

To determine tire clearance, subtractthe section width from the figure fordual spacing. Use the loaded sectionwidth (LS) at rated load for a more exactclearance figure. The loaded sectionwidth can be found in the GoodyearTruck Tire Engineering Data Book, orthe width of a tire can be measuredunder load.

Dual spacing and tire clearance canbe varied by changing spacer width. To increase spacer width, however, themounting width on the dual wheel mustbe great enough to accommodate awider spacer. The distance from the outside tire wall of one dual assembly tothe outside tire wall of the assembly onthe other side of the truck will be madegreater when spacer width is increased.If this distance is the maximum width ofthe vehicle, state laws governing truckwidth must be considered.

Rim offset determines dual spacingand affects vehicle clearance and possiblyoverall vehicle width. Any change in offset of the inside rim will change vehicle clearance proportionally. Anyoffset changes of the outside rims willchange the overall distance across thevehicle from outside tire wall to outsidetire wall.

Both load and inflation must be considered in selecting rim size or type. Consult rim manufacturer for recommended rim style for extra ply rating tires.

SPACERSSpacer installation procedure is as

follows:1. Examine spacer brand to be sure it

is not damaged, bent, or distorted. It should be perfectly circular.

2. Do not roll vehicle, wheels, axle, or assemblies on spacers.

3. Position inside rim over cast spokewheel as close as possible to themounting level.

4. Push spacer band over cast spokewheel with consistent pressure onboth sides. Avoid cocking band.Achieve snug fit against spokes andinside rim gutter edge.

5. Turn spacer band on wheel to checkconcentricity.

6. Position outside rim, install outerrim clamps and tighten nuts evenly. Tighten nuts gradually in a criss-cross sequence across thediameter of the wheels. Consult rim manufacturer’s recommendationsfor proper torque range.

7. Examine clamps to be sure theyhave not bottomed out. Check rimedges to be sure they consistentlymeet the spacer band edges.

8. After road service, recheck torque.

SPACING OF DUALS

Figure 3.9 Cross-section through typical dual installation

Section Width

Dual Spacing

Offset Offset

CL CL

Section Width

Tire

Cle

aran

ce

Veh

icle

Cle

aran

ce

Spac

er

Wid

th


27

Mounting Procedure

Most highway rims look alike, but allvary somewhat in certain constructionfeatures. Variances between rims of different types make part mixing hazardous. A close, proper fit betweenrim parts is essential to long tire life aswell as operating safety. Although siderings, flanges, and lock rings of differenttypes appear to be properly seated, difficult to detect gaps are often present.

The illustrations in Figure 3.10show correct, safe matchings of rimparts. Mismatched rings and bases,which almost always create an unsafeoperating condition are also shown. Formore information, refer to Departmentof Transportation (DOT) MultipieceRim/Wheel Matching Chart.(www.dot.gov)

In addition to the safety problemsposed by mismatched rings and bases,mismatched components can cause specialproblems in tire, flap, and tube wear.

Mismatched rim components thatresult in a high bead seat often achievebead seating over only a portion of therim circumference. This causes:

• Vibration• Uneven wear• Severe rim chafing at top of flange• Larger gaps in two piece rim flanges

which cut chafer• Torn chafers at bead heel• Cut bead heels, which generally

identify this condition• Bead base irregular chafing• Lower sidewall separation due to

stress concentration at flange top• Broken beads

Mismatched assemblies that result in a low bead seat can sometimes be recognized by rust on the bead face.Such assemblies allow:

• Irregular bead base wear• Off-center mounting, higher

imbalance, more vibration• Rotational slippage of tire on rim• Valve stem tear-outs

Rim component mismatch — witheither high or low bead seat diameter —permits bead rocking which can causethe tire bead toe to cut through the flap and tube. This additional beadmovement can also cause the flap edgeto cut through the tube. In either case, a flat tire is the eventual result.

PROPER MATCHINGOF RIM PARTS

Figure 3.10 Correct and incorrect matching of rim parts

Motor Wheel or Accuride “CR” or “FL” Side Ring

Motor Wheel or Accuride “CR” and “FL” Bases and Components Interchangeable With Accuride “CR” and “FL”

Motor Wheel “LB” Bases and Components Interchangeable With Accuride and Budd “LB”

Motor Wheel or Accuride “CR” or “FL” Base

Motor Wheel LW and LB Base Accuride or Budd LB Base Motor Wheel LW Side Ring

Accuride or Budd LB Side Ring

Proper Fit

Proper Fit

Proper Fit

Accuride 5˚ or Motor Wheel “CR” or “FL” Flange

Motor Wheel or Accuride “CR” or “FL” Lock Ring

CORRECT

INCORRECTAccuride 5˚ Lock Ring “CR” / “FL” Side Ring

Bead Seat Too High“LW” or “LB” Base

Loose Fit“CR” or “FL” Base

“LW” Side Ring

Bead Seat Too High Improper SeatingImproper Seating

“CR” or “FL” Flange & Lock Ring “LW” or “LB” Base

“CR” or “FL” Base Loose Fit

Improper Seating


28

Mounting Procedure

• Clean rims and repaint to stop detrimental effects of corrosion andfacilitate checking and tire mounting.Be very careful to clean all dirt andrust from the lock ring and gutter.This is important to insure that thelock ring seats in its proper position. A filter on the air inflation equipmentto remove the moisture from the airline helps prevent corrosion. The filtershould be checked periodically to seethat it is working properly.

Parts must be clean for a proper fit —particularly the gutter section whichholds the lock ring in proper position.

• Components that are cracked, badlyworn, damaged, bent, repaired, or pittedfrom corrosion must not be used andmust be discarded. When componentcondition is in doubt, replace.

Parts that are cracked, damaged orexcessively corroded are weakened.

SAFETY PRECAUTIONSInspection: Precautions And Reasons For Precautions

• Do not, under any circumstances,attempt to rework, weld, heat, or brazeany rim components that are cracked,broken, or damaged. Replace withnew parts or parts that are not cracked,broken, or damaged and which are of the same size and type and arecompatible with the other parts.

Heating may weaken a part to theextent it is unable to withstand forcesof inflation or operation.

• Make sure correct parts are beingassembled. Check your distributor or the manufacturer if you have any doubts.

Mismatched parts may appear to fit,but when the tire is inflated may flyapart with explosive force sufficient to cause serious injury or death.

• Don’t be careless or take chances. If you are not sure about the propermating of rim and wheel parts, consulta rim and wheel expert. This may bethe tire man who is servicing yourfleet, the rim and wheel distributor in your area, or the manufacturer’ssales engineer.

Failure to exercise proper care canresult in serious physical injury or death.

• Don’t reinflate a tire that has been runflat or has been run at 80 percent orless of its recommended operatingpressure, or when there is obvious orsuspected damage to the tire or wheelcomponents.

Components may have been damagedor dislocated during the time the tirewas run flat or seriously underinflated.


29

Mounting Procedure

Underinflated truck tires can be subjectto cord fatigue in the upper sidewall areacaused by over-flexing of the tire. Thiscord fatigue leads to a loss of strength ofthe ply cords. When a tire loses air andis continued in service without remedialaction, it may sustain internal damagethat could lead to failure upon reinflationor subsequent service. When such a tire is reinflated, or removed from the rim (for example, for tire repair or maintenance) and then remounted, inflation used to bring the tire to itsoperating pressure may cause one ormore of the weakened cords to break.This cord failure causes an increase intension on cords adjacent to the brokencord, with the result that more of theweakened cords may fail. This breakagemay continue until a rupture occurs inthis area of the tire with accompanyingair loss, which is commonly referred toas a Zipper Rupture.

Permanent tire damage due to underinflated operation cannot always be detected. Any tire known or suspectedto have run at 80% or less of normaloperating inflation pressure could possiblyhave permanent structural damage andshould be treated as having been operatedflat or underinflated. The tire should bedemounted using proper precautions andshould not be reinflated until the tire iscarefully inspected by a trained technicianfor determination of the cause of theinflation loss, and any possible strucural.damage. (See pages 29 - 31)

GOODYEAR STRONGLY RECOMMENDS THAT:• Truck tires should be visually inspected

daily for cuts, snags, penetrations orpuncturing objects.

• Proper tire inflation be maintained.

• Highway truck tire inflations bechecked at least weekly, or more frequently if operating conditions dictate, using an accurate calibratedair gauge.

• Any tires suspected to have beenoperated underinflated must be clearlymarked and segregated, so as to prevent their accidental use prior to being thoroughly inspected by a trained tire technician.

• Tires that show discoloration andwrinkling of the innerliner, and/orweakness and distortion of the uppersidewall (indications of damage due to underinflation) are to be scrapped.

• After servicing the tire, inflate it to 20 psi OVER recommended operatingpressure in an APPROVED SAFETYCAGE USING A CLIP-ON CHUCK,EXTENSION HOSE AND PRESSUREREGULATOR. Allow the tire to remainoverinflated for 20 minutes and thendeflate to the recommended operatingpressure BEFORE removing from thesafety cage.

• Goodyear’s long-standing policy and Occupational Safety and Health Administration (www.osha.org)Standard 1910.177, require that alltubeless and tube type truck tires beinflated in an OSHA approved inflation safety cage in conjunctionwith the use of an extension air hoseequipped with a clip-on air chuck.

• While this OSHA standard pertainsto medium truck tires, Goodyearstrongly recommends these proceduresbe used for all LIGHT TRUCK tires also.

UNLESS THE PRECAUTIONSNOTED ABOVE ARE CAREFULLYAND COMPLETELY FOLLOWED,SUCH FAILURE MAY CAUSE SERIOUS PERSONAL INJURY OR DEATH.

MOUNTING AND INFLATION:Precautions For Potential Steel Cord Fatigue Damage


30

Mounting Procedure

• Always match a tire (size) diameterdesignation with exactly the same rimdiameter designation. Don’t assumethat it came in with proper size.

• Rims of different diameters and taperscannot be interchanged.

• Don’t try to seat rings or other components by hammering while tireis inflated or partially inflated.

• Never introduce a flammable substanceinto a tire — before, during or after mounting.

Doing so is unsafe and may result ininternal tire damage or fire, rim damage or a potentially dangerousvapor remaining in the tire. Any ofthese conditions could cause seriouspersonal injury during the mountingand inflating procedure.

• Double check to make sure all components are properly seated prior to and after inflation.

• Always inflate in a safety cage or use another restraining device that isapproved by the Occupational Safetyand Health Administration(www.osha.gov).

• Don’t inflate a tire before all components are properly in place.Place assembly in a safety cage or useanother restraining device and inflateto approximately 10 psi. Recheckcomponents for proper assembly.Observe that the O-ring does not rollout of its groove. If the assembly is not proper, deflate and correct. Neverhammer on an inflated or partiallyinflated tire/rim assembly. If the assembly is proper at approximately 10 psi, continue to inflate to fully seatthe tire beads.

If tube type, inflate tire to approximately 75 psi pressure(Grader, 50 psi). Then completelydeflate to remove buckles and unevenstresses from the tube and flap beforereinflating to correct operating pressure.This repeat inflation is necessary toprevent buckles which may lead topremature tube failures.

After completing inflation, checkvalve and rim components in bothbead areas for leaks. Observe tirelower sidewall circumferential groove’sconcentricity with top of flange. If thedistance between the groove and rimflange varies by 1/8'' or more aroundthe circumference or from one beadto the other, the tire beads must be unseated from the bead seat, relubricated and reseated.

• Never sit on or stand in front of, orover, a tire and rim assembly that isbeing inflated. During inflation, alwaysuse a clip-on chuck with sufficientlength of hose to permit standingclear of the potential trajectory of thewheel components, and use an in-linevalve with gauge or a pressure regulatorpreset to a desired value when inflatinga tire. When a tire is in a restrainingdevice, do not lean any part of yourbody or equipment on or against therestraining device.

If parts are improperly installed theymay fly apart with explosive force sufficient to cause serious injury ordeath. Rapid air loss can propel an assembly.

• Follow recommended mounting, demounting, inflating and deflatingprocedures for tires and rims as outlined in this manual.

Misassembled parts may fly apart during inflation: check at 10 psi todetermine whether parts are in proper position.

• Don’t hammer on rims or componentswith steel hammers. Use rubber, lead,plastic or brass faced mallets if it isnecessary to tap uninflated componentstogether. Mallet faces should be ingood condition to avoid chips frommallet face inside of the components.

Properly matched and assembledcomponents will seat without tapping.If a part is tapped, it or the tappingtool may fly out with explosive force.

• When moving a tire or wheel with a cable or chain sling, stand clear.

The cable or chain may break, lashout and cause serious injury.

• Never attempt to weld on an inflated tire/rim assembly or on a rim assembly with a deflated tire.

Heat from welding will cause a sudden,drastic increase in pressure, oftenresulting in a large, explosive force.Deflated tires can catch fire inside theair chamber.

• Mixing parts of one type rim with thoseof another is extremely dangerous.Always check manufacturer forapproval if in doubt.

MOUNTING AND INFLATION:Precautions And Reasons For Precautions


31

Mounting Procedure

• Always use rims recommended for thetire. Consult catalogues for propertire/rim matching.

• Don’t overload or overinflate tire/rimassemblies. Check for adequate rimstrength if special operating conditionsare anticipated.

Excessive overload or overinflation can cause damage to the tire and rim assembly.

• Never run a vehicle on one tire of a dual assembly.

The carrying capacity of the single tireand rim is dangerously exceeded, andoperating a vehicle in this manner canresult in damage to the rim and tire orcause a tire fire.

• Never use a tube in a tubeless tire/rimassembly where the rim is suspected of leaking.

Loss of air pressure through fatiguecracks or other fractures in a tubelessrim warns you of a potential rim failure.This safety feature is lost when tubesare used with leaking rims. Continueduse may cause the rim to burst withexplosive force.

• Always inspect rims and wheels fordamage during tire checks.

Early detection of potential rim failures may prevent serious injury.

• Never add or remove an attachment or otherwise modify a rim (especiallyby heating, welding or brazing) unlessthe tire has been removed andapproval has been received from the rim manufacturer.

Modification or heating of a rim orone of its parts may weaken it so thatit cannot withstand forces created by inflation or operation.

• Block the tire and wheel on the opposite side of the vehicle beforeplacing the jack in position.

• Regardless of how hard or firm theground appears, put hardwood blocks

under the jack. Always provide forvehicle support with blocks just incase the jack should slip.

The vehicle may shift, slip off the jackand cause injury.

Inspection Procedures For Identification Of Potential “Zipper Ruptures” In Steel Cord Radial Medium And Light Truck TiresAny tire suspected of having been operated underinflated and/or overloadedmust be approached with caution.Completely deflate the tire by removingthe valve core before removing thetire/rim/wheel assembly from the vehicle. After removing from the vehicle,clearly identify the tire, so it will not bereinflated until carefully inspected by atrained technician, to determine thecause of inflation loss, as well as any tiredamage resulting from underinflationand/or overloading.

OPERATION:Precautions And Reasons For Precautions

WARNINGPermanent tire damage due tounderinflation and/or overloadingcannot always be detected. Anytire known or suspected to havebeen run at 80% or less of normaloperating inflation pressure and/oroverloaded, could possibly havepermanent structural damage(steel cord fatigue). Ply cordsweakened by underinflationand/or overloading may break one after another, until a ruptureoccurs in the upper sidewall withaccompanying instantaneous airloss and large explosive force.This can result in serious injury or death.

SERVICING TIRE AND RIM ON VEHICLE:Precautions And Reasons For Precautions


32

Mounting Procedure

Inspect DeflatedSuspect Tires Mountedon the Rim –

LOOK for:cuts, snags, or chips exposing body

cords or steel*; distortions or undulations(ripples and/or bulges), using an indirectlight source, which will produce shadowsleft by any sidewall irregularities.

FEEL for:soft spots in the sidewall flex area;

distortions or undulations (ripple and/orbulges); protruding filaments indicatingbroken cords; and

LISTEN for:any popping sound when feeling for

soft spots or when rolling the tire.

If any of these conditions are present,the tire should be made unusable andscrapped. *If no other condition ispresent and a tire contains cuts, snags,or chips exposing body cords or steel,it must be referred to a full-servicerepair facility, to determine if it isrepairable and not a source of a potential zipper.

If none of these conditions are present,place the tire/rim/wheel assembly in an approved inflation safety cage.REMAIN OUTSIDE OF THE TIRE’STRAJECTORY. DO NOT PLACEHANDS IN SAFETY CAGE WHILEINSPECTING TIRE, OR PLACEHEAD CLOSE TO SAFETY CAGE.With the valve core removed, reinflatethe tire to 20 psi, using a clip-on airchuck with a pressure regulator and an extension air hose.

Inspect SuspectTire Inflatedto 20 psi —

LOOK for:distortions or undulations (ripples

and/or bulges); and

LISTEN for:any popping sound.

If any of these conditions are present,the tire should be made unusable and scrapped.

If none of these conditions are present, dismount the tire to visuallyand manually inspect it, both inside and outside.

Inspect SuspectTires afterDismounting —

LOOK for:bead rubber torn to the fabric or

steel*; cuts, snags, or chips exposingbody cords or steel*; distortions orundulations (ripples and/or bulges),using an indirect light source, which willproduce shadows left by any sidewallirregularities; creasing, wrinkling, cracking or possible discoloration of the innerliner; and any other signs ofweakness in the upper sidewall.

If any of these conditions are present, the tire should be made unusable and scrapped. *If no othercondition is present and a tire containscuts, snags, or chips exposing bodycords or steel, it must be referred to afull-service repair facility, to determineif it is repairable and not a source of apotential zipper.

If none of these conditions are present, the tire may be returned toservice, using the procedures on thenext page.

Inspection Procedures For Tires Suspected Of Having Been Run Underinflated And/Or Overloaded

WARNINGSTAY OUT OF TRAJECTORY AS INDICATED BY SHADED AREA.Note: Under some circumstances, the trajectory may deviate from itsexpected path. Always deflate tiresbefore handling. Inflate only insafety cage.

A B C


33

Mounting Procedure

Inspect DismountedTires (including used, retreaded, or repaired)–

LOOK for:bead rubber torn to the fabric or steel*;

cuts, snags or chips exposing body cordsor steel*; distortions or undulations (ripples and/or bulges), using an indirectlight source, which will produce shadowsleft by any sidewall irregularities; creasing,wrinkling, cracking, or discoloration of the innerliner; any other signs ofweakness in the upper sidewall;

FEEL for:soft spots in the sidewall flex area;

distortions or undulations (ripplesand/or bulges); protruding filamentsindicating broken cords; and

LISTEN for:any popping sound when feeling for

soft spots or when rolling the tire.

If any of these conditions are present,the tire should be made unusable andscrapped. *If no other condition ispresent and a tire contains tears, cuts,snags, or chips exposing body cords or steel, it must be referred to a full-service repair facility, to determine if it is repairable and not a source of a potential zipper.

If none of these conditions are present,place the tire/rim/wheel assembly in an approved inflation safety cage.REMAIN OUTSIDE OF THE TIRE’STRAJECTORY. DO NOT PLACEHANDS IN SAFETY CAGE WHILEINSPECTING TIRE, OR PLACEHEAD CLOSE TO SAFETY CAGE.After properly seating the beads, withthe valve core removed, adjust the tireto 20 psi, using a clip-on air chuck witha pressure regulator and an extension air hose.

Inspect MountedTires Inflatedto 20 psi —


and/or bulges); and



If none of these conditions are present,with valve core still removed, inflate thetire to 20 psi OVER the recommendedoperating pressure. During this step, if any of the above conditions appear,immediately stop inflation.

Inspect Mounted TiresInflated 20 psi OVEROperating Pressure —


and/or bulges): and


Any tire suspected of having beenunderinflated and/or overloaded mustremain in the safety cage at 20 psiOVER operating pressure for 20 minutes.


If none of these conditions are present,BEFORE removing the tire/rim/wheelassembly from the safety cage, reducethe inflation pressure to the recommendedoperating pressure. REMAIN OUTSIDEOF THE TIRE’S TRAJECTORY.

Occupational Safety and Health Administration

Standard 1910.177 requires all tubeless and tube-type

medium and large truck tires be inflated using an

OSHA-approved restraining device (e.g. safety cage)

or barrier, and using a clip-on air chuck with a

pressure regulator and an extension air hose. While

the OSHA (www.osha.gov) standard pertains to

medium and large truck tires, RMA also strongly

recommends these procedures be used for all LIGHT

TRUCK TIRES.

A B C

WARNINGMounting Tires Is Dangerous - failure to follow the above andRubber Manufacturer‘s Association(RMA) “Demounting and MountingProcedures for Truck/Bus Tires” or “Demounting and MountingProcedures for Automobiles andLight Truck Tires” charts and safetyprecautions can result in seriousinjury or death. For more informationvisit www.rma.org.

Inspection Procedures For All Tires Returning to Service (Including used, retreaded, or repaired, regardless of being suspect or not suspect)

Collecting & Storing

Tire Information

S E C T I O N F O U R

Keeping appropriate records of your tire

related data is the best source of information

on tire performance, because they summarize

your actual experience based on your

equipment, your drivers, and your operating

environment. They can help you to make

cost effective tire purchase decisions and

adjustments to tire and wheel maintenance

schedules to better control costs.

34

Collecting &Storing TireInformation


35


Depending on the size of your fleet,tire data can be kept using a computer-aided method or simple paper files. Largefleets may need the huge informationstorage capacity and the networkingcapability of a computer. Small fleetsmay find the expense and complicationsof computer-aided information storageunnecessary. Whatever the method ofstorage, there are several common factorsinvolved in tire data collection. Itemsrecorded for tire performance records, at a minimum, should include:

By building a base of informationacross the fleet, trends in tire performancecan be established.

• How does mileage of Tire A compare to Tire B?

• Which tire brand produces the lowestcost per mile?

• Which tire has fewest adjustments?

A similar file can be used to track tireperformance through retread life. Again,performance of various tread patterns,retread suppliers, and casing manufacturerscan be closely followed. Decisions onfuture retread purchases can then be madeon hard facts rather than perceptionsand guesses.

Permanent identification of each tirecan make the tracking from purchase to scrap easier. Tires could be branded,or a Radio Frequency Identification Chip could be added to the tire to provide a unique identity for that tire.

• Tire Size• Tire Brand/Type• Initial Tire Cost• Vehicle ID

Number• Vehicle Mileage

at Installation• Installation Date• Tread Depth at

Installation

• RecommendedInflation

• GeneralComments

• Actual Inflation• Vehicle Removal

Mileage• Removal Date• Tread Depth

Removal

COLLECTING & STORING TIREINFORMATION BRANDING TIRES

Several branding methods exist. Beforebranding, you need answers to severalquestions. What branding method is bestfor the quantities of tires involved? Onwhat part of the tire is it “safe” to brand? How deep can a tire be branded without damaging the tire? Should you buy tiresbranded to your specifications or brandthem yourself? Many fleets brand theirown tires. Others, particularly large fleets,find it more cost-effective purchasingtires branded by the manufacturer or distributor. Three common brandingmethods include the “cold method,” “hot method” and “mold branding.”

Cold branding is somewhat of a misnomer because some heat is part ofthe procedure. In this method, pressure,air or hydraulic, is used to produce abrand that is legible and usually lessdamaging to the tire than the highertemperature hot method. Another advantage to cold branding is its abilityto emboss brand. Numbers and lettersare raised much like the markings on a new tire. Embossed brands are lessdamaging to the tire than the more common recessed brands though oftenmore difficult to read.

Both cold and hot methods providepermanent brands but the higher temperatures of a hot branding ironencourage branding too deeply into thesidewall. Also possible is overheating therubber compound around the brand andcreating a brittle surface area that couldinitiate sidewall crack. If care is exercised,the hot method using medium heat willyield acceptable results. Always strive for the lowest possible temperature toproduce legible brands without scorchingsidewall rubber.

A third method is “mold branding.”This is done when the tire is being manufactured. While this method offersthe best appearance, it’s available onlywhen large quantities of tires are orderedand usually for only bias-ply tires.

Use lower sidewall area. Most trucktires have a special branding panel onthe sidewall. It’s located on the lowerportion of the sidewall where little flexing occurs under normal use, thusreducing the chances of cracking.

If your tires don’t have these panels,then brand in the lower sidewall areabetween the top of the rim flange andthe “line” around the tire at its maximumwidth. Never brand near the maximumsection width area of a radial tire. That’sthe tire’s critical sidewall flexing area. If you’re branding tires without panelsand wish to brand both sides, then apply brands on opposite sidewalls 180 degrees apart.

How deep?In general, you should brand truck

tires between 1/32 inch and 2/32 inch indepth. Brands less than this depth rangeare often difficult to read. Those greatercan result in cracking that may propagateaway from the branded area, or worse,they may go deeper into the sidewallrubber. Eventually, these deep cracksmight reach the outer surface of the casing cords. This could allow moistureinto the casing which then could lead to degradation of casing durability.


36


RADIO FREQUENCYIDENTIFICATION TAGS

Passive radio frequency (“RF”) identification devices can be moldedinto a tire or encapsulated in a patchand bonded to the inner liner of radial,medium and heavy duty, tubeless trucktires. Guidelines have been establishedby the Technology and Maintenance Council(www.tmc.truckline.com) to standardizethe identification information providedby an RF transponder when it is installedduring the tire manufacturing process,used in an aftermarket application in truck tires and provide minimum performance criteria for the use of this technology.

The transponder is a single chip,solid state, electronic device with anintegral or external antenna. Each tagthat passes within the radio frequencytransmission range of a reader/interrogatorwill be energized and have its circuitturned on. In turn, the tag will respondby transmitting its encoded identification.The reader will receive the RF transmittedcode and translate it into an alpha-numeric tire identification.

Fleets may use RF tags for tire recordkeeping and maintenance as well as inventory. To ensure that RF tags are easily read and correlated with the proper tires, the following tire mountingprocedures should be followed:A. Always mount tires with the DOT

code side on the deep dish rim sideof disc wheels, the fixed flange sideof tube type demountable rims and the adapter side of tubelessdemountable rims.

B. The DOT code should be alignedwith the valve stem so that local readRF tags can be located and foundeasily except in cases where matchmounting takes a priority.

C. Local read tags will then be readableon opposite sides when mounted asduals and will be readable on theinside of the steering axle except for directionally mounted tires.

D. 360 degree read tags are not restrictedby mounting.

Having well documented tire performance information allows intelligentdecisions to be made on alignmentintervals, recommended inflation pressures and tire brand or type choices.

Keeping appropriate records of tireinformation is a final step in achieving alower cost per mile from tires. Havingclear records not only helps decisionmaking but also provides documentationof tire problems to be addressed by yourtire company’s representative.

After all, your goal as well as the goalof your tire representative is to provideyou with the best tire for the job and toget all the mileage and service out ofyour tires that they can give.

RF TAG USAGE

Inflation

S E C T I O N F I V E

Proper inflation of radial truck tires is the

most important maintenance practice to

ensure long tire life. Once proper tire

inflation has been determined, it should be

maintained at that level as consistently as

possible. Loads carried may be increased/

decreased for a given tire inflation when

operating at reduced/increased speeds,

but underinflation must never be allowed

in over-the-road truck tires.

37

Inflation


38

Inflation

A tire requires proper air pressure to adequately carry the load placed on it. The “container volume,” materialproperties and inflation pressure determinethe load carrying capacity of the tire.Figure 5.1 Your tires provide traction forbraking, accelerating and turning andmust carry out these tasks for manymiles. Without proper inflation pressure,tires cannot carry out these tasks as theywere designed to do.

But what is the proper inflation foryour tires? A simple answer would begreat, but not practical.

Loads determine inflationAll tire manufacturers offer load/

inflation tables that can be used to determine the proper inflation pressureat various loads.

Load/inflation tables for Goodyearcommercial tires are published on theWeb site www.godyear.com/truck and in theEngineering Data Book for Over-the-RoadTruck Tires. This book, available at yourGoodyear Commercial Truck Tire Center,and is updated periodically with the latestsizes and types of commercial truck tires.

Section “L” in this data book providesthe information you’ll need to determinethe proper inflation for your tires based

on load and service conditions. Most datacontained in this book is taken from tablespublished by the Tire & Rim Association(T&RA). Its members, U.S.-based tire,rim and wheel manufacturers, set thetechnical standards for manufacturingthose products in this country.

Using the tables is quite simple. First,determine the maximum load that yourtire is likely to encounter. Then, for yourtire size/ply rating, find the load in thetable that is close to but slightly morethan the maximum anticipated load. Theinflation pressure at the top of this columnis your minimum pressure for the load.

Duals vs. singlesNote that loads are shown for single

and dual applications. When you runduals, the allowable load at any giveninflation pressure will be less than withsingles. That’s to minimize overloadingwhen one tire in a dual assembly isunderinflated and to compensate forroad crown.

Position is another consideration. Steer,drive and trailer tires may carry differentloads, with steer tires normally handlingthe heaviest because they run as singles.

To optimize tire performance, you mayrequire different inflation pressures in

each axle position. That would be ideal,but impractical for many linehaul fleets.

Equal inflation pressureTo compromise, determine the proper

inflation pressure for each tire on thevehicle and use the highest pressure.Remember that overinflation is preferredto underinflation. That makes the compromise acceptable.

Also consider operating speeds.Vehicles operated at less than highwayspeeds can carry greater loads, as shownin Table 3.

Using load/inflation tables can helpyou get the most from your current tires.It can also help you choose future tiresizes based on your vehicles’ needs andtheir service conditions.

Always check inflation pressures whentires are cold. Never bleed air from hottires to relieve normal pressure build-up.The normal increase in pressure due toservice conditions will be 10 to 15 psi,and this is allowable in a radial truck tire.

It is particularly important to keepmoisture from the inside of any tires andwe strongly encourage proper selectionof compressor equipment, air-line routing,and the use of air dryers to avoid moisturein high pressure air used for inflation.

Figure 5.1

LOADContainerVolume


39

Inflation

TABLE 3TRUCK-BUS TIRES

The service load and minimum (cold) inflation must comply with the following limitations:

SPEED RANGE INFLATION PRESSURE INCREASE LOAD CHANGES WITH SPEED(MPH) RADIAL PLY TIRES RADIAL PLY TIRES

CONVENTIONAL (STD. PROFILE) WIDEBASE/METRIC (LOW PROFILE) CONVENTIONAL WIDE BASE/METRIC 65 MPH 75 MPH 65 MPH 75 MPH 65 MPH 75 MPH 65 MPH 75 MPH

71 thru 75 + 5 PSI None + 5 PSI None - 12% None - 12% None66 thru 70 + 5 PSI None + 5 PSI None - 4% None - 4% None51 thru 65 None None None None None None None None41 thru 50 None None None None + 9% + 9% + 7% + 7%31 thru 40 None None None None + 16% + 16% + 9% + 9%21 thru 30 + 10 PSI + 10 PSI + 10 PSI + 10 PSI + 24% + 24% + 12% + 12%11 thru 20 + 15 PSI + 15 PSI + 15 PSI + 15 PSI + 32% + 32% + 17% + 17%6 thru 101) + 30 PSI + 30 PSI + 20 PSI + 20 PSI + 60% + 60% + 25% + 25%2.6 thru 51) + 30 PSI + 30 PSI + 20 PSI + 20 PSI + 85% + 85% + 45% + 45%

Creep thru 2.51) 2) + 30 PSI + 30 PSI + 20 PSI + 20 PSI + 115% + 115% + 55% + 55%Creep + 40 PSI + 40 PSI + 30 PSI + 30 PSI + 140% + 140% + 75% + 75%

Stationary1) + 40 PSI + 40 PSI + 30 PSI + 30 PSI + 185% + 185% + 105% + 105%

1) On conventional tires apply load increase to dual loads and inflations only, even if tire is in single application. 2) Creep–motion for not over 200 feet in a 30 minute period.

Table 3

Source: The Tire & Rim Association Yearbook


40

Inflation

A tire’s cold inflation pressure willchange with altitude and temperature.The air pressure gauge reads the differencebetween the tire’s contained air pressureand atmospheric pressure. Atmosphericpressure changes 0.48 psi for every 1000feet change in altitude. Assuming constanttemperature and internal tire volume, if a tire pressure gauge reads 100 psi atsea level, for every 1000 feet increase in altitude, the gauge will read 0.5 psihigher inflation pressure, see Figure 5.2.

Since this difference is small, the effectof altitude change on tire inflation, ingeneral, is not considered to be significant.

Ambient temperature effects on atire’s cold inflation pressure, on the otherhand, is significant. Using as an examplea tire with an initial inflation pressure of 100 psi at 60 degree F ambient temperature, for each 10 degree F changein temperature, there is about a 2 psichange in the tire’s inflation pressure, see Figure 5.3.

The inflation pressure reading at 0 degree F might happen when the truckis parked on a cold winter night. It willincrease rapidly, though, once the truckbegins to run and the tires warm up. At the other extreme of ambient temperatures, for example during thesummer, it is common to find tire inflationpressures in the 115 to 120 psi range.We always caution operators not tobleed air pressure down on cold tireswhen they are at these higher ambienttemperature conditions. Always inflatetires cold to the required pressure nomatter whaat the ambient temperature is.

UNDERINFLATIONUnderinflation can have detrimental

effects on the performance of your tiresand vehicles. Increased tire wear rate,irregular treadwear, reduced casing durability and lower fuel economy aresome of the unnecessary costs incurredfrom tires not properly inflated.

Running on underinflated tires costsyou in lost tread life and higher fuel consumption. Tests conducted byGoodyear have shown that just 15 percent underinflation of steer, drive and trailer tires results in about an 8 percent drop in expected tread mileageand a 2.5 percent decrease in miles pergallon, Figure 5.4.

Altitude (feet)

Infl

atio

n P

ress

ure

(p

si)

0

100

101

102

103

104

105

1000 2000 3000 4000 5000

Figure 5.2

Under Inflation (percent)

Exp

ecte

d M

ilea

ge (

per

cen

t)

100

90

80

70

600 10 20 30

Figure 5.4

Ambient Temperature (deg F)

Infl

atio

n P

ress

ure

(p

si)

0

80

90

100

110

120

20 40 60 80 100 120 140

Figure 5.3


41

Inflation

The damage doesn’t end there. With the capabilities of today’s trucktires, underinflation is also detrimentalto your tires’ potential for multipleretreads as well as sustained operation in today’s service conditions.

Underinflation can cause casing damage and thus diminish the tire’s abilityas an “air container.” This is of specialconcern since today’s radial tires arecapable of running much longer thanthe life of their original treads.

No spare aboardAdd to this fact that many fleets don’t

carry spare tires anymore. Althoughfleet inflation pressure maintenance hasimproved over the years, sometime overtheir working life, today’s truck tires arestill likely to run underinflated or flat.Continued running this way can ºseriously damage the casings.

Sidewall flexing increases noticeablywhen a tire’s inflation drops 15 to 20percent below recommended. Excessiveflexing can result in cord fatigue andbroken cords, and cords adjacent tothese are subjected to greater tensionwhen the tire is reinflated. The potentialfor a sidewall rupture then becomes very great.

Excessive heat does often cause theliner to wrinkle and discolor, and theupper sidewall to visibly distort and discolor.

Check psi weeklyPaying close attention to inflation

pressures and to tires that have rununderinflated has never been moreimportant, considering the potential for sidewall ruptures, the value ofretreadable casings, and the cost of tire related downtime.

The tire industry recommends checking inflation pressures once eachweek on all tires. This check should bemade with a calibrated tire gauge or agauge that is checked periodically witha gauge known to be accurate.

Another valuable tip is to use a sealingmetal or nylon valve cap or a quality“air-through” type cap. Plastic caps donot provide a secondary seal to the outdoor environment, and no cap at all allows dirt, water and other foreignmaterials into the valve. Their presenceinvites air leakage.

Carefully inspect any tires that havebeen repaired or now have cuts, snags orother penetrations. Scrap any that showdefinite signs of underinflation. Mark atire that looks suspicious in any way andset it aside for a thorough inspection bya trained tire technician.

When inflating or reinflating tires,always use a tire safety cage. This holdstrue for both tube-type and tubelesstires. The past few years have seen adecline in the use of tire cages, becauseof the growing popularity of tubelesstires. Some consider the cage necessaryonly when inflating the complex assemblies of a tube-type tire and rim.We strongly recommend using a tirecage regardless of the wheel or rim type.

The evolution of the radial tire has madeit a long wearing, durable component of today’s trucks. We should keep inmind that “radial” is not synonymouswith “indestructible”, and that properinflation is the primary key to preservingradial tires’ outstanding qualities.

UNDERINFLATIONCAN CAUSE:

• Separations• Circumferential Breaks• Higher Risk of Road Hazard• Loss of Fuel Economy• Uneven/Irregular Wear• Higher Risk of Road Hazard• Higher Downtime Expense• Loss of Casing Durability


42

Inflation

DO• Do maintain proper minimum inflation

for load carried per the Goodyear recommended table

• Do maintain mated dual tires at equal inflation

• Do use sealing-type valve caps

• Do check inflation at frequent intervals

• Do keep inflation air dry

DON’T• Don’t permit tires to operate

underinflated

• Don’t “bleed” air from warm tires to relieve pressure buildup

• Don’t reduce tire pressure to obtain a softer ride

• Don’t run with one tire of a dualassembly at low pressure or flat

• Don’t inflate to cold pressures beyondrated rim capacity

Over the years, nitrogen inflation hasbeen proposed for various types of tires,including large earthmover tires downthrough small passenger tires. At thepresent time, Goodyear endorses nitrogeninflation for certain sizes of earthmovertires used in particular applications, andhas issued detailed instructions for thesetires. Anyone concerned with applyingor maintaining earthmover tires shouldbe aware of the Goodyear ServiceDepartment Bulletins and Off-the-RoadTire Training Manuals that contain detailsof nitrogen inflation recommendationsfor these large off-the-road tires.

The issue of nitrogen inflation forover-the-road truck tires is not quite soclear. Various performance improvementshave been claimed, including bettertreadwear, casing durability, and reduced susceptibility to tire fires.

Although little actual controlled testdata exists, a summary of Goodyear’sexperience with nitrogen inflation fortruck tires is the basis for the followingcomments. Treadwear appears to beaffected negligibly by the tire inflationmedium. Specifically, there is little, ifany, tread life change to be expected byusing nitrogen inflation compared tonormal air. So far as casing durabilityand retreadability are concerned, the primary criteria is to avoid moisture inwhatever inflation medium is used. Tothis end, we strongly encourage properselection of compressor equipment, air-line routing, the use of air dryers, and other good shop practices to avoidthe introduction of moisture into highpressure air used for both initial tireinflation and make-up air. Again, weknow of no significantly improved casingdurability or retread durability performanceto be expected from nitrogen inflation inover-the-road truck tires.

Reduced rim or wheel corrosion hasalso been cited as an advantage of nitrogeninflation. However, corrosion is primarilythe result of excessive moisture introducedby air that has not been properly dried,rather than a direct result of air versusnitrogen inflation.

An additional concern is that paststudies have shown that a very small percentage of non-nitrogen make-upinflation significantly contaminates thecontained nitrogen atmosphere within atire. In other words, if any benefits are to accrue from nitrogen inflation, it isessential that virtually all make-up inflationthroughout the life of the tire/wheelassembly be diligently controlled to assurea near 100 percent nitrogen environment.

A final issue is that of insuring againsttire fires and/or self-ignition of tiresresulting from excessive heat. For trucktires, this concern has been greatlyreduced in recent years, primarilybecause of the changes from bias to radial tires and from tube-type to tubelesstires. The tubeless radial tire is simplymuch less susceptible to a tire fire than a bias tube-type design. This is partlybecause of the simplicity of the tubelessdesign (i.e. no separate tube and flap tocreate heat from rubbing or internal friction when the assembly deflates orruns severely underinflated or overloaded),and partly because steel radial truck tiresrequire higher temperatures for a fire tostart than their fabric-reinforced bias-plycounterparts.

In summary, nitrogen inflationappears to have significant advantagesfor certain sizes and applications of largeoff-road tires, especially those operatingin extremely high load or speed environments. However, nitrogen inflation appears to have quite small,perhaps insignificant, advantages forover-the-road truck tires.

DO’S AND DON’TSFOR MAINTAININGPROPER INFLATIONPRESSURE NITROGEN INFLATION

Total Vehicle

Alignment

S E C T I O N S I X

Vehicle alignment settings serve several

purposes in vehicle operation. They affect

handling, steerability, stability and have a

significant impact on tire performance.

Camber settings are not considered

adjustable in the field.

NEVER ATTEMPT TO ADJUST

THESE SETTINGS BY BENDING

OR MODIFYING AXLE/STEERING

MECHANISM COMPONENTS.

43

Total VehicleAlignment

S E C T I O N S I X

44


Figure 6.1 Toe-in

Figure 6.2 Toe-out

Figure 6.3 Positive camber Figure 6.4 Negative camber

Front of Vehicle

Front of Vehicle

The long treadwear potential offeredby modern radial linehaul truck tires canbe reduced by the misalignment of tractorand/or trailer wheels and axles. Extensiveresearch has demonstrated that totalvehicle alignment programs can pay dividends in extended tire wear andimproved fuel economy.

There has been increased attention toproper truck alignment procedures duringthe past few years, and for good reason.Current radial steer axle tires provide amuch slower rate of wear than earliergeneration radial or bias ply tires. Thisalso means that they may reflect theadverse effects of improper alignmentthat was unseen on faster wearing tires.

Opinions on proper alignment forradial tires often seem as varied as thenumber of authorities giving them. Forthis reason, Goodyear has been activelyinvolved in working toward industrywide agreement to define the effects of improper alignment on tire wear,durability and vehicle handling, and to establish recommended alignment settings.

Much of this work is being directedthrough industry associations includingThe Maintenance Council of AmericanTrucking Association, The Society of Automotive Engineers and with individual OEM truck, axle and suspension manufacturers.

S E C T I O N S I X

45


In particular, certain truck and axlemanufacturers have responded to therequirements for more precise alignmentsettings. These OEM’s do not recommenddelivery realignment of their vehicles atthe dealer level.

Specific irregular wear patterns andtheir causes are discussed in detail in the “Irregular Wear” section of this service manual.

Years ago, alignment meant simply a“front-end job”. But the steer axle is onlythe beginning of the total alignmentstory in the radial age.

We now know that proper attentionto drive axles, trailer axles and dollyaxles completes the picture. Not onlydoes alignment affect tire wear, but theamount of fuel used by a truck/trailercombination as well. (See Section 9 for additional details).

STEER AXLEALIGNMENT

LOADED VS UNLOADEDALIGNMENT SETTINGS

The major front-end alignment settings involve:Toe:

Toe is defined as the difference in distance apart, at the front and at therear, of the steering-axle tires as seenin a top view of the truck. Toe-inexists when the tires are closer togetherin the front than in the rear Figure 6.1and excessive toe-in results in featherwear in the direction shown by thearrows. Toe-out exists when the tiresare closer together in the rear than inthe front Figure 6.2 and excessive toeout results in the feather wear in thedirection shown by the arrows.

Camber:Camber is the tilt of the tires as seenin a front view of the truck. Positivecamber exists when the tires are closertogether at the bottom (point of roadcontact) Figure 6.3. Negative camber exists when the tires are closer togetherat the top Figure 6.4.

Caster:Positive caster is provided by a backward (rotational) tilt of the top of the axle or backward inclination of the kingpin at the top as seen in a side view of the truck Figure 6.5.Negative caster would be a corresponding tilt forward at the top.

Before any alignment adjustment isperformed, always check the vehicle forloose kingpins, worn wheel bearings, tierod ends, or any looseness in the steeringsystem. Adjust wheel bearing end playin accordance with the recommendationsof the OE manufacturer. Attempts tocorrect alignment on a vehicle withworn or loose components are pointless.

Alignment changes as load changes,especially steer axle camber, caster andtoe. Since springs, axles and suspensionmountings vary by truck and componentswith different weight ratings are oftenchosen, different unloaded truck alignment settings may be required toobtain optimum loaded truck alignments.

On steer axles, toe and camber settingsare related and should be consideredtogether for optimum tire life, especiallyin line-haul service where treadwearrates are slow. Positive camber (refer toillustration) creates a slightly shorterrolling radius on the outside shoulder ofa radial tire than on the inside shoulder.This creates a tendency for the tire toroll toward the outside—a toe-out condition. Since all the working tolerances in the tie-rod ends and kingpins must be taken up before the tendency to toe-out is restrained, an initial static toe-in setting is essential.

Figure 6.5 Caster

NOTEAlignment recommendations mayneed to be “customized” for certainvehicle/tire/service conditions.

S E C T I O N S I X

46


Toe settings generally have the greatest effect on truck tire treadwear.Toe is also the easiest front-end alignmentvariable to adjust in the shop.

Road tests were made using threetrucks with different amounts of loadedtruck toe-in (1/32-inch, 1/8-inch and1/4-inch) with radial tires on the steering axles.

The test results showed:• Tire tread mileage decreases with

increased toe-in. The 1/32-inch toe-inshowed the best treadwear rate(miles per 32nd of tread depth).

• Assigning a value of 100 to thetreadwear rate with 1/32-inch toe-in,the treadwear rate values comparedas follows:

In addition to wear, drivers’ reactionsto the toe-in settings, without powersteering indicated that the 1/4-inch toe-incaused the truck to “roadwalk” badly.The 1/32-inch value was considered to have the best handling.

Tire wear due to excessive toe-in onradial tires shows up initially as irregularwear — more so on the outside than theinside grooves of the tires and more so onthe right-front than on the left-front tire.Excessive toe-out will show a reversedeffect: more wear on the inside than theoutside grooves and more so on the left-front than the right-front tire.

At high values of toe-in or toe-outand at relatively early mileage, the treadof the outside or inside ribs can be completely worn away. For 5/16-inchtoe-in condition this can occur afteronly 19,000 miles of highway travel.

Gauges for measuring toe-in settingare relatively simple and inexpensive.Every maintenance shop should usethem frequently. It is not necessary tosend a truck to an alignment shop tocheck toe-in settings.

Setting toe alone is usually not sufficient. A total vehicle alignment (toe and axle) is recommended perTMC RP642.

CAMBERAfter years of recommending camber

settings of +1/4 degree for left front and0 degrees for right front, major axlemanufacturers have changed to 0 degreesettings for both left and right steer axlepositions on axles designed for line haul service.

The objective of this change is tooptimize steer tire wear and minimize oreliminate irregular wear. Theoretically,these new settings will result in steertires running straight down the road in a 0 toe/0 camber mode. GoodyearProving Ground tests and independentfield tests support this theory.

Tires with excessive camber will wearas shown in Figure 6.6. It can be seenthat improper camber causes wear onone side of the tire, this can be on theinside or outside of the tire dependingon camber setting and tire position (LF or RF).

CASTERGenerally, caster is not considered to

affect tire wear, but is important in thehandling and driveability of the vehicle.

Overall effects of caster can be summarized as follows:—Too little caster causes:

• Unstable steering• Constant corrections required• Wander and weave• Oversteer• Failure to return to straight ahead

out of a turn• Roadwalk

—Too much caster causes:• Hard steering• Shimmy• Road shockVehicle manufacturers normally

recommend caster settings for theirvehicles. Proper caster is that whichgives best handling in combination with the camber and king pin inclinationdesigned into the axle.

TOE

LoadedToe-inValue

(Inches)

1/321/81/4

ComparativeTreadwear

Rates

1008276

Figure 6.6

Camber WearOne side of thread worn excessively

S E C T I O N S I X

47


There are many variables to checkwhen determining the source of irregulartire wear patterns. One potential causefor irregular wear on steer tires may be a truck’s “Ackermann” characteristic.

The Ackermann Principle states thatfor any given corner, the outside wheelshould have less turn angle than theinside one, because it is following a larger radius than the inside wheelFigure 6.7.

This difference in wheel turningangles is determined by the length andangle of the steering arms that areattached to the hubs of the steer axle.

The theoretical Ackermann angle for a particular vehicle is determined bydrawing a line through the pivoting axis

(which is the rear axle of a two-axlevehicle) to establish a pivot point for a turn; then drawing lines to the pivotpoints of the two steer tires. TheAckermann, then, is the angle the tires/wheels needed to be turned to form a right angle with each of the linesextending from the turning pivot pointto the tire/wheel pivots. This results inthe steer tires “toeing out” when turning.A vehicle’s wheelbase is the most criticalvariable affecting the “theoreticalAckermann” for a vehicle.

Keep in mind that Ackermann is apurely geometric concept. The argumentthat the Ackermann Principle was developed in the early 1900’s for veryslow-moving vehicles and does not

consider the dynamic effect of manyoutside influences on the path a vehicletakes through a turn is somewhat correct.

To further complicate the AckermannPrinciple as it applies to trucks, rememberthat the turning axis must be drawn todetermine a pivoting point about whichthe vehicle turns. It’s more difficult todefine this axis for vehicles with morethan one drive axle. Fifth wheels,depending on their location, can alsoalter where this line would fall.

The trend is for vehicle manufacturersto provide different Ackermann arms for different wheel bases and differentfleet vocations.

ACKERMANN STEERING EFFECT ON TIRE WEAR

Figure 6.7

• DefinitionThe Ackermann PrincipleStates that for Any GivenCorner the Outside WheelShould Have Less TurnAngle Because It IsRunning at a LargerRadius than the Inside Wheel.

Ackermann Principle

S E C T I O N S I X

48


Drive axle alignment is very important.Tandem drive axles that are not parallelto each other have a definite effect onsteer-tire wear.

Figure 6.8 shows a model of a tandem-drive-axle tractor with both drive axlesin proper alignment. In this case, thedriver simply steers the truck straightahead and neither fast wear nor irregularwear would be expected as a result of the driving axles.

However, Figure 6.9 is an exaggeratedview of a truck with drive axles parallel,but not perpendicular, to the chassis centerline. The eight driving tires createa “thrust angle” to the left at the rear ofthe truck. Turning the steering wheelslightly to the left aligns the steer anddrive tires to run parallel, but the vehiclehowever will “dog track.” Even thoughlateral forces on the steer tires are minimal,the steering geometry is affected, whichmay result in asymmetrical steer tire wear.

A more severe case is shown in Figure 6.10. Here the drive axles areneither parallel to each other nor perpendicular to the chassis centerline.The drive-axle tires are trying to forcethe vehicle to turn left and the drivermust compensate by turning to the right.This will result in fast and irregular wearand, as recent tests have shown, in amuch more severe way than the previouscase. These tests also indicated that thesteer tire on the same side of the truckon which the drive tires are closesttogether will wear into an out-of-roundcondition as well.

Recommendations for drive-axle alignment are as follows:

•Tandem axles should be parallelwithin 1/8-inch difference betweenthe axles centers measured on theleft and the right side of the vehicle.Figure 6.11

•Axles should be perpendicular to thechassis centerline within 1/8- inchmeasured between axle end andvehicle centerline. Figure 6.12

Figure 6.8

Figure 6.9

Figure 6.10

DRIVE AXLE ALIGNMENT

S E C T I O N S I X

49


TRAILER AXLEALIGNMENT

IN-SERVICEALIGNMENTRECOMMENDATIONS

With more long-wearing radial tiresbeing applied to trailer axles, their alignment has become an important issue.Trailer-axle tires have the potential forlonger life (more miles per thirty-secondinch of treadwear) than any of the tires onthe tractor. They are, therefore, moresusceptible to irregular wear due to misalignment than any other tires onthe vehicle.

Goodyear’s recommendations for trailer alignment are as follows:

Preferred toe setting: 1/32-inch toe-in to 1/32-inch toe-out, or ±2.7 minutes per spindle.Acceptable toe setting: 1/16-inch toe-in to 1/16-inch toe-out,or ±5.4 minutes per spindle.

The loaded axle camber can be up to negative 1° without affecting tire wear.

Axles should be parallel to each otherwithin 1/8-inch measured betweenaxles on both sides of the trailer at a 71.5-inch axle track. This providesa scrub angle of ±0.1°.

Axles should be perpendicular to thecenterline of the trailer frame within1/8-inch per side or 1/4-inch fromside to side at a 71.5-inch axle track.This provides a thrust angle of ±0.2°.

Toe-in is recognized throughout theindustry as the most important contributorto optimizing steer tire treadwear. In order of priority, gains in tread life canbe expected by focusing on the following vehicle alignment parameters:• TOE• REAR TANDEM PARALLELISM• CAMBER (NON-ADJUSTABLE)• REAR TANDEM PERPENDICULARITY• CASTER

Most vehicle manufacturers, in recentyears, have developed new factoryequipment and procedures to controlalignment to much narrower tolerancesthan was previously possible. Todaythere is less need to adjust alignment on new vehicles than in the past.

Alignment accuracy and repeatabilitycan best be achieved by proper training,adherence to strict procedures and byproperly maintaining and frequently calibrating alignment equipment.

THE VEHICLE MANUFACTURER’SALIGNMENT SPECIFICATIONSSHOULD BE ADHERED TO.

The following guidelines have proved to be beneficial for improving overall tire treadwear:

STEER AXLESTOE IN (unloaded):

Check Limits* 1/16'' ± 1/16''(Range 0-1/8'')Reset Limits 1/16'' ± 1/32''

*When alignments are found withinthese limits, adjustment is not necessary. If outside of check lim-its, set to the reset limits.

DRIVE AXLESTandem axles to be parallel within1/8'' measured at axle end.

Axles to be perpendicular to chassiscenterline within 1/8'' when measuredfrom axle end to chassis centerline,or within 1/4'' when measured fromleft to right axle end.

TRAILER AXLESTandem axles to be parallel within1/8'' measured at axle end.

Axles to be perpendicular to chassiscenterline within 1/8'' when measuredfrom axle end to chassis centerline,or within 1/4'' when measured fromleft to right axle end.

Nominal toe setting:0'' ± 1/32''

Reference TMC RecommendedPractice RP642 regarding total vehiclealignment for more detailed information.

Figure 6.11

Figure 6.12

•Rear Tandem Parallelism

•Rear Tandem Perpendicularity

A = B within 1/8 inch

A = B within 1/4 inch

A B

A B

Factors

Affecting

Treadwear

S E C T I O N S E V E N

Alignment problems are often blamed for all

irregular treadwear. However, many other

factors can be responsible for, or contribute

to, irregular wear. While the wear pattern

can often suggest the cause of the problem,

it sometimes takes real detective work to

track down and correct the real source

of trouble.

50

FactorsAffectingTreadwear


51


The issue of irregular tire wear hasalways been a concern even in the dayswhen most trucks ran bias ply tires. Withtoday’s longer wearing radial tires, irregular wear has surfaced as the primaryconcern of most truck maintenance managers. In fact, it is the ability of today’sadvanced radial tires to deliver long original tread life which requires evenmore attention to good maintenancepractices and vehicle alignment.

Radial tires have a different footprintshape than bias tires. See Figure 7.1.This results in less scrubbing and longertread life. However, this same attributeof the radial design can also result in thetire exhibiting more irregular wear whenvehicle and tire maintenance are belowpar. These wear patterns are not as evident

in bias ply tires. Since the tread wearsaway usually much faster on bias tires,unusual wear patterns are literallyscrubbed off as they develop.

The Technology & MaintenanceCouncil (TMC) of the AmericanTrucking Association has publicly saidthat the positive attributes of the radialtire, particularly longer tread life, can result in the tire exhibiting moreirregular wear patterns when vehicle andtire maintenance or tire construction is inadequate.

The TMC has also published anexcellent reference guide titled Radial TireConditions Analysis Guide. This bookletclearly defines the types of irregular wearcommon to steer, drive, and trailer axlesand offers possible reasons that suchwear occurs. Figure 7.2.

Contact The Technolgy &Maintenance Council at http://tmc.truckline.com or order publicationsthrough The ATA Marketplace: 1-800-282-5463.

Figure 7.1 A bias tire footprint is oval shaped… the radial footprint is rectangular.

Figure 7.2 Radial Tire Conditions Analysis Guide— an excellent reference book.

Footprint Shapes

Bias Radial

ALIGNMENT

DUAL

MATCHING

INFLATION

BALANCING

TIRE

SELECTION


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STEER TIRE WEARUneven or irregular tire wear is a

widespread problem in today’s truckingindustry. All brands of rib tires haveexperienced this undesirable situation.

Extensive testing has proven thatvehicles with lightly loaded front axlesare more prone to irregular steer tire wearthan those with heavily loaded frontends Figure 7.3. By lightly loaded, we’retalking about a front axle configurationof 10,000 to 10,500 pounds or less forthe typical linehaul-sized tires. We alsoknow that tractors with wheelbases morethan 200 to 210 inches long are alsocandidates for irregular steer tire wear.

Several factors help determine steer tireload. These include vehicle configuration,wheelbase, axle set-back and fifth wheelposition. How this load contacts theroad surface is then influenced by alignment settings. Vehicle toe, camber,caster, drive axle parallelism and perpendicularity are important factors in steer tire wear patterns.

All things considered, how a tiretread wears depends on the forces thatact upon the contact patch of that tire as it meets the road.

If a tire is highly loaded, it tends to have a square footprint shape. Theshoulder rib contact area is very long,about the same length as the center ribs.As the tire rotates, contact with the roadis good.

By contrast, a lightly loaded tire tendsto have very short shoulder ribs, muchshorter than the center rib. As this tirerotates, the footprint center maintainsvery good contact but the shoulder area does not. This causes much morescrubbing action and wearing away ofthe shoulder rib.

Vehicle misalignment, non-parallel or non-perpendicular drive axles and suspension system problems naturallyaffect steer tire wear.

While many fleet owners and maintenance personnel believe they have heavily loaded steer axle applications,they’re running with loads in the 10,000to 10,500 pound range and below. HeavyGVW doesn’t equate with heavy frontaxle load.

Tire inflation also plays a role in tirewear. Once loading is determined, youmust run your tires at the proper inflationto match loading. Your tire companyrepresentative should help you determineoptimum inflation for that configuration.

A good rule of thumb — inflate tothe T & RA recommended pressurerequired for the load plus 10 psi. Thiswill compensate for tire-to-tire variationsand normal leakage.

Periodic inspections of your vehicleand tires are a must. Look for signs ofirregular wear or vehicle componentproblems. Then take immediate action to correct these problems.

And finally, work very closely withyour tire company representative todetermine the right tire for the application.A tire designed for highway use, forexample, may not be the best choice forrunning off-road. Tires, like trucks, arebuilt to do specific jobs. Defining thatmission is a good first step.

Figure 7.3

Load/Footprint Comparison

KEY IRREGULAR WEAR CONDITIONS

DEFINEDChamfer wear — A nibbling orerosion that occurs on the outsideedge of the shoulder ribs of a tire.This condition typically resultsfrom slow rate of wear line-haulservice and does not indicate a tireor vehicle problem.

Erosion or river wear — A nibblingeffect at the edge of the interiorribs of a tread design. It’s most oftenseen on very slow wearing tires inline-haul steer applications.

Fast rib wear — One or more ofthe interior ribs of a tire wear awaymuch more rapidly than the adjacent ribs. Tire construction,itself, may be the cause.

Diagonal wear — Rapid wearingaway of a diagonal patch of thetread design. Causes are generallynon-tire related. Probable suspectsinclude mismounting a tire on thewheel, brake or bearing problems.Diagonal tire wear is not caused by a heavy splice or componentending in a tire.

Fast shoulder wear — Rapid wearing away of one or both tireshoulders on steer axle position.The problem shows up as smoothrapid wear or a scalloped “islandwear” configuration as the tire runs.


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SETBACK STEER AXLESThough increasingly popular today,

“setback” steer axles are not new to thetrucking industry. For many years, “setback”front axles have been used in on/off roadapplications in construction, oil field,waste hauling and specialized services.

The primary benefits of “setback”steer axles are improved maneuverability,more desirable load distribution and, inmany cases, improved ride. The applicationof “setbacks” to over-the-road linehaultype trucks, however, is fairly recent.

The term “setback” is relative, andsome designs are more setback than others.Generally, the axle of a modern “setback”linehaul tractor is positioned about 13 to15 inches behind its traditional position.This design is typically found on longconventional and medium conventionalcab models.

More pronounced “super setbacks” areusually found on COE models where theaxle is positioned about 25 inches behindits normal position. Collectively, all truckswith “setback” axles can be expected topresent distinct characteristics which canaffect tire selection and usage patterns.These include shorter wheelbases, highersteer tire loads, higher wheel cut angles.

While these characteristics are “setback”steer axle benefits, there are others thatcan adversely affect tire wear.

Steer tire inflation pressuresAs a general rule, irregular wear

tendencies are more of a problem ontrucks with lightly loaded steer axles.This is especially true of trucks pullingheavy loads where high drawbar forceon the kingpin tends to unload the steeraxle when the truck is rolling. Rearwardpositioned fifth wheels offer furtheropportunities to reduce steer axle loads.

“Setback” axle trucks tend to haveheavier steer tire loading both staticallyand dynamically. This is because most ofthem also employ extensive aerodynamicpackages that restrict fifth wheel placementflexibility. In fact, some “super setback”designs can have nearly identical steertire loadings from bobtail to fully loaded condition.

Tires on the “super setbacks” must workharder, and in some cases, require higherinflation pressures to support the increasedloads. Load/inflation pressure tables areavailable from www.goodyear.com/truck,Engineering Data Book or Over-the-RoadTruck Tires, or a qualified tire companyrepresentative.

If higher steer tire pressures arerequired, this may mean you’ll be usingdifferent inflation pressures for drive and trail tires.

Increased lateral tire scrubAs the wheelbase dimension shortens,

steer tires must generate an increasingamount of side force to turn the truckchassis when cornering. This is especiallytrue for tandem drive axle units. As an example, compare a tractor with a140-inch wheelbase with one whosewheelbase is 230 inches Figure 7.4.Steer tires on the shorter vehicle mustgenerate 65 percent more corneringforce to slide the tandems around a

Loaded vs. unloaded alignment anglesDifferences in payload can also affect

steer tire loading differently, dependingon fifth wheel location, suspension typeand degree of axle setback. Therefore,you can’t continue to assume traditionalchanges in toe, camber and caster frombobtail condition (typical when checkingalignment) to fully loaded. In fact, certain“setback” axle designs have shown nocamber change.

Toe change, on the other hand, canrange from no change to a decrease, or,in some cases, to an increase with addi-tional load. Caster change may also bedifferent from model to model, sincemost “setback” axle designs also employsprings that are longer or have differentdeflection characteristics.

Ackermann steering geometry While Ackermann geometry has not

typically been a major problem on linehaul type vehicles, it should now beconsidered because most “setback” axledesigns also incorporate increased wheel cut angles. The industry standardfor many years has been in the 32- to34-degree range. Now typically in new designs are wheel cuts of 42 to 44degrees, meaning steer tires are likely tobe scrubbed more severely when turning.As a result, the effects of improper orcompromised Ackermann geometry willbe more pronounced.

Suspension damping controlDamping control has also become

more important, since many “setback”axle designs employ softer riding suspensions. The older stacked springdesigns had considerable leaf-to-leaf friction, which tended to act as a built-inshock absorber. This damping also variedwith loading.

Now, depending on the specific suspension, damping control can becomecritical. Shock absorbers should be properly sized, maintained and replacedwhen necessary to control suspensionmovement, which, in turn, leads to tirewear irregularities.

corner. The normal result will be fasteroverall steer tire wear rates than experienced by the longer wheelbaseunit. Another result will be less irregularwear because the extra scrubbing tendsto clean up uneven wear patterns as theydevelop. You’ll also find tires with widertreads or more massive tread rib designswill usually perform better on the shorterwheelbase vehicles.

Figure 7.4

Truck Wheelbase Effects on Steer Tire Wear

Shorter wheelbase truck must develop more cornering force with steer tires to generate the same cornering moment to turn truck

or to counteract a chassis thrust angle

230

140


54


DRIVE TIRESLet’s review some of the key elements

that impact drive tire wear:

Engine Torque (More usable torquemeans less tread life)

Engine torque is measured in foot-pounds of twisting force without regardto time. Peak torque on many of today’sengines occurs at lower engine rpms andremains at a relatively high level over awide rpm range. A typical engine mightdevelop 1,200 to 1,250 foot-pounds ofpeak torque at only 1,300 rpms.

High engine torque over a wide rpmrange adversely affects drive tires, whichtransmit this higher torque to the highway.Increased stress, deflection, deformationand reduced tread life result.

Highway Speeds (Faster speeds mean less tread life)

Linehaul tractor trailers are now permitted to travel at 65 mph in ruralareas in place of 55 mph in 71 percent of the states. At 65 mph, that means a16-percent tread life penalty, accordingto one study. Experts cite as causesincreased tire footprint deformation andhigher tire running temperatures.

Inexperienced Drivers (Tread life can suffer)

High turnover means truckload and irregular route drivers are less experiencedthan in the past. Driver turnover surpasses100 percent annually in some fleets.Inexperienced drivers can abuse theirvehicles with rough gear shifting, spinning wheels on wet surfaces and fast accelerating and braking.

Setback Steer Axles (Affect drive tire wear)

Setback steer axles were engineered toimprove vehicle comfort, load distributionand vehicle maneuverability. A tractor’swheelbase is shorter when its steer axleis placed 13 to 15 inches behind theusual position (or up to 25 inches in thecase of super setback axles). Shorterwheelbases mean greater wheel cutangles, from the normal 30 degrees up to42 inches in some cases. Smaller turningradii are the result of higher cut angles.

But tighter turns equate to higher cornering forces in the drive tire footprintand reduced tread life. Depending on thepercentage of straight-ahead highwaydriving, these forces can also cause reartandems to wear much faster than forward tandems.

Rear Suspensions (Service/maintenance sensitive)

Good suspension and shock maintenance is critical to obtain longtread life and uniform wear. Inadequatecare can cause uncontrolled jounce andrebound, and over long time periods,irregular drive tire wear as well.

Empty backhauls can aggravate the problem. Lightly loaded trucks with leafspring suspensions and deep tread tirescan develop a cyclic bouncing process,particularly on rutted or deterioratinghighways and highly crowned roads.Significant tread life losses and variousdegrees of irregular wear can result.

Extreme variations in air pressures ofdual wheel assemblies is another majorcause of reduced tread life and also ofirregular drive tire treadwear. Fleets thatdon’t control air pressures of duals ineffect allow the tire with lower air pressureto overdeflect, deform, scrub excessivelyand non-uniformly and eventually developirregular drive tire wear.

Here are some tips to obtaining desirable drive tire tread life with minimumirregular wear:

• Recognize the effect of vehicles, service and operating conditions on drive tire tread life.

• Train drivers in proper operating techniques.

• Exercise speed control.• Maintain rear axle/tandem alignment.• Balance air pressure between duals.


55


Suspension systems are changing.Early trucks were stiffly sprung with suspensions similar to horse-drawn buggies. Today, the demand is for a softer ride. Better driver and passengercomfort is one reason. Another is a need to protect delicate cargo such aselectronic equipment and computers. Forthese and other reasons, air suspensionsare becoming more popular.

There are two basic suspension systems. A taper leaf is used primarily on steer axles and trailer axles. Air suspensions are used mainly on driveaxles and trailer axles, but are now being introduced on steer axles. Besidesa softer ride, air suspensions provide fullsuspension movement regardless of loadcondition and the ability to equalize theload between axles. Radial tires work best when in firm contact with the road surface.

Suspension systems are a combinationof springs and dampers (shock absorbers).Older, multiple-leaf spring suspensions hadso much leaf-to-leaf friction that they werevirtually self-damping Figure 7.5. Today’staper-leaf systems, with fewer leaves andspace between leaves, produce little self-damping. In fact, a low friction materialoften is placed between the leaves to reducedamping. Air bags also lack self-damping.

Placement of shocks in the suspensionsystem can help or hinder their effectiveness.Consider, for example, shocks mountednear the center of the frame. Bump inputsto both the right and left sides of the axle – such as road expansion joints – areproperly damped. But a bump input toone side or the other results in the axlerotating about its center. There is littleshock compression or extension and littledamping of axle movement.

Fluid leaks around the shock’s pistonrod are a sign that shocks should bereplaced. Replace a shock absorber ifone end is disconnected or if the shockcan be easily compressed and extended.

Temperature is another way to checkshock effectiveness. After a truck returnsfrom a highway run, a mechanic shouldtouch the shock absorber. A warm shockis working, a cold shock is not.

With air suspensions, shock absorbersare also considered the “stops” at theextended end of the suspension travel.

Present and future trucks will havesofter, more compliant suspensions thatprovide many advantages over older systems. Proper maintenance of thesesuspensions will assure the benefits ofthese systems are realized without a negative impact on tire life.

Vehicles should be spec’d consideringride and tirewear. Frequent suspensionsystem maintenance assures maximumtreadwear and tire life.

BEARING ADJUSTMENTAsk five different fleet maintenance

managers about how wheel bearingadjustments affect alignment settings andyou’re likely to get five different answers.They’ll likely agree that axle end play isa tire wear concern but the reasons whymay not be fully understood.

Axle end play is an indicator of wheel bearing adjustment. End play is themovement, in and out, of the tire/wheel/hub assembly at the end of the axle. Mostvehicle and axle manufacturers say .001-inch to .005-inch end play isacceptable. Trailer manufacturers mayallow up to .020 inch. You need a dialindicator to measure this movementaccurately, but experienced mechanicsand technicians can grab the tire at twopoints 180 degrees apart and detect in-and-out movement by giving theassembly a wiggle. Not a precise measurement by any means, but experienced hands can usually tell if there is too much play, flagging the need for maintenance.

Figure 7.5 Taper-Leaf springs produce little self-dampening.

SHOCK ABSORBERS —3 CONSIDERATIONS

• Selection. For maximum effectiveness, select the rightshock absorber for the job.Consult with a manufacturer’srepresentative to make theproper choice.

• Placement. Proper placementof shock absorbers in a suspension system ensuresoptimum shock compressionor extension and axle movement damping.

• Maintenance. Regularly checkshock absorbers to make surethey are performing adequately.Replace shocks when they are worn.

Leaf Springs

Stacked Multiple Leaves(Much Leaf to Leaf Friction)

Taper Leaf(Little Leaf to Leaf Friction)


56


Axle end play changes camber andtoe setting. For example, pushing in thetop of the assembly and pulling out at thebottom will change camber angle. Similarly,pushing on the front side of the tirewhile pulling on the rear alters toe setting,which raises the obvious question: “Howmuch change in camber and toe doeswheel bearing end play cause?”

The amount of change can be predicted with mathematical calculations.The graph in Figure 7.6 shows camber change for a given amount ofend play.

If end play and bearing taper angleare known, calculations may be used todetermine the diametral clearance (DC)of both inner and outer bearings. Then,knowing the distance between the bearings,the angle change is found using the following formula:

1/2 DC (Inner Bearings) x 1/2 DC(Outer Bearing)

Distance between bearings

A .020-inch end play will only changethe camber about 1/8 of a degree. Cambertolerance is commonly plus or minus 1/4of a degree, so if end play is kept withinspec, the camber change caused by thisamount of play is insignificant.

But tolerances are closer for toe. Toesetting is commonly expressed as the difference in distance from the tractorcenter line to the front and rear edge of each tire as measured at hub centerheight. Recommended settings for over-the-road trucks are:Steer axles:

Toe in 1/16'' ± 1/32'' (unloaded)For trailer axles:

0 ± 1/32''We also calculated possible toe-in

change at various end play settings.Remember, toe in is the relationshipbetween front and rear sides of one tire,so we can look at toe change due to endplay on one side or both sides of thevehicle. The graph in Figure 7.7 illus-trates our findings.

If both sides of the steer axle are atmaximum allowable end play, toe changeof .080 (more than 1/16) inch couldresult. That’s a very significant differencebecause maximum allowable toe toleranceis only 1/32-inch. So you should keepend play on steer axles well below accepted maximums to get longest tire life.

Maintain within specs for longer tirewear. Obviously, any tire/wheel/ hubassemblies that are outside the currentspec for axle end play have potential fortire wear problems. And they won’t goaway. Excessive end play prevents setting

toe properly so irregular tire wear will bechronic if end play is not within spec.

Some experienced mechanics claimimproved tire and bearing life with “preloaded” bearings. In addition, somelong-life, low maintenance wheel systemsare being offered that require a preloadedbearing arrangement as part of theirstandard installation requirements. Toavoid overtorquing these systems, a greatdeal of care must be used to achieve aproper bearing preload. As a result, themanufacturer’s recommendations shouldbe closely followed.

Bearing manufacturers strongly discourage overtorquing a bearing just toeliminate servicing after a break-in period.Although you get more bearing and tirewear, a too-loose bearing is safer on anover-the-road truck than a too-tight one:the overtorqued bearing can heat up,may crack and could cause a dangerousaxle failure on the road.

We urge you to limit axle end play to the low end of the specified tolerancerange and follow the manufacturer’s recommendations when preload isrequired. Make periodic end play checkswhen permitted by the manufacturer tomaintain tight settings. The payoff willbe more accurate toe adjustment, saferoperation and longer tire life, particularlyfor high mileage radials.

ENVIRONMENTALEFFECTS

Road surfaces and environmental factors play a big factor in tire performanceand tread life. An understanding of theeffect pavement conditions have on treadwear can help fleet managers analyzevariables in overall tire costs. Engineeringstudies have drawn conclusions aboutthe following variables:

Road surface textures on treadwear Tire engineers agree that rough, sharp

surfaces and those with embedded shellsare more abrasive and tend to generatefaster wear rates than polished concrete andsmooth asphalt. Rough surfaces create ahigher scrub force, which accelerates

Total Camber Change (˚)

Max. Recommended By Most ManufacturersEn

d P

lay

(in

)

.020

.015

.010

.005

0 .02 .04 .06 .08 .10 .12

Figure 7.6

End Play vs. Camber

End Playvs. ToeChange

or CamberChange

Figure 7.7

End Play vs. Toe Change or Camber Change


57


Road Surface Wear RatingHot mix asphalt 100Concrete 90Crushed rock asphalt 65Dirt 50

treadwear. (Tests show coarse chip andseal pavement increased rolling resistanceby 33 percent over concrete.)

To illustrate, engineers have designedindoor laboratory tests and imposedextreme conditions on sets of similartires. In one specific example, they foundabrasive surfaces can create a 100 percentworn situation in as little as 1,000 miles.Meanwhile, the same tires evaluated onpolished/ worn surfaces typically wereonly 25 percent worn after 2,000 miles.

While far from real road conditions, thetests showed a wear rating improvementfor the smooth surfaces of 800 percent.Under actual conditions, the tires wouldhave run much farther in both cases.

Fresh concrete is tough on tires. Inoutdoor tests, engineers found treadwearrates were 70 percent faster on month-oldpavement than on 24-month-old concrete.Reason: Over time, traffic wears down theabrasive edges of the fresh surface.

If we were to assign wear ratings toseveral different road surface materials,the differences would be significant. Dirt, for example, would rate approxi-mately 50 while hot mix asphalt wouldscore 100. Higher numbers indicatetreadwear mileage.

Grades and tire wearToday’s high torque/low rpm diesel

engines have changed typical drivingtechniques for truckers from “slow uphill/fast downhill” to more constant speeds. Butthis added torque to the drive wheels hasalso created greater driveline and tire stressover extended time periods. Steep gradesthemselves add to this stress.The two factorssubject tires to higher longitudinal forcesin the tire footprint area. This conditionleads to tire slip, abrasion and wear.

Those carriers operating in the mountains, for instance, can experience50 percent faster treadwear than carriersoperating on relatively flat terrain.

Curves and tread lifeMore curves, lower tread life. That’s

because curve-imposed side forces causelateral tire deflection and deformation.Tests show frictional forces during specificcornering can be 5.8 times as great aswhen driving straight. During braking,frictional forces can be 2.4 times as great.

Climate and tire wearWater acts as a lubricant. Tires that

often travel over wet pavements canshow up to 30 percent longer treadwearthan tires that run only on dry pavements.Temperature is also a factor. When thetemperature increases, so do treadwearrates. For example, when roads are wet,fleets typically obtain better treadwear in the fall and winter verses spring and summer.

Driving technique plays a major rolein maximizing tire life, but so doeswhere the vehicle is driven.

HOW SPEED AFFECTSTIRE WEAR

In 1995, Congress repealed thenational 55 mph maximum speed limit.By early summer 1996, 10 states hadraised the truck limit to 75 mph, sevenothers to 70 mph and 22 states to 65.

If you’re running where 75 mph signsare found, you might shave two hoursfrom a 500-mile trip. That assumes noextra rest stops, no construction slowdownsor any slowdowns at all. But surveys showthat faster drivers take more breaks dueto stress, refuel more often, suffer morebreakdowns and expose themselves tomore potential accidents.

Conclusion: a faster 20 mph speeddoes not often translate into a 20 mphfaster average over the long haul.

And what does rolling in the fast lanedo to your rig?

First, there is the fuel penalty. The ruleof thumb says for every 1 mph over 55,your semi’s fuel economy goes down by0.1 mpg. So, running 75 instead of 55may cost you 2 mpg, or 33 percent ifyour truck averages 6 mpg.

Even running 65 mph vs. 55 costs you1 mpg or an extra 2.5 cents per mile.

Also affected directly is tire performance.The faster you roll, the more heat your tire casing creates. This degradescasing durability, promotes irregulartreadwear, shortens tread life and reduces impact resistance.

Casing durability: The extra heatassociated with running faster will affectyour tire casings over time. If you’re currently averaging two retreads per casing, you may only average 1.5 to 1.75retreads per casing by running at higherspeed limits.

Running hotter can take its toll onrubber. A good example is in the tire’sshoulder area, where the belt edge of thetop steel belt can obtain temperatures upto 180 degrees F running continuously at 75 mph. At 55 mph, belt edge temperatures average 160 degrees F. The increased temperature degrades casing durability, especially in the second and third retread stages.

Accelerated Treadwear: Tests showthat every 1 mph increase over 55 mphresults in 1 percent reduction in treadmileage. So, running at 75 mph insteadof 55 may cost your fleet 20 percent inremoval miles.

Irregular wear: As your truck speedincreases, your tires flex more, resulting ina different footprint. Going from 55 to 75mph causes the tread centerline to lengthen,which can cause tire shoulders to developcupping and overall fast shoulder wear.

Impact resistance: Your tire’s resistanceto sidewall snags and tread area puncturesis reduced at higher running speedsbecause of higher rubber temperatures.Expect more incidents of road damage at higher speeds.

How can truckers minimize thesenegative factors? Be sure to maintainproper air inflation pressure. Runningunderinflated will accelerate all the problems associated with higher speeds.

Ride Disturbance

S E C T I O N E I G H T

Vibration in modern over-the-road trucks

can affect driver comfort (and, therefore,

productivity), cargo safety, and equipment

wear. As with most other problems, vibration

can have a number of different sources and

an effective solution requires that the cause

(or causes) be accurately determined.

58

RideDisturbance


59

RideDisturbance

Concern for truck vibration problemshas increased in recent years as truckshave evolved to fill today’s more demandingtrucking industry needs. Several currentdesign trends (e.g. longer wheel bases)have resulted in trucks that are more susceptible to vibration problems.

For increased driver comfort andreduced cargo damage, many over-the-roadsuspension systems are now designed to be “softer” than in the past. This isaccomplished in part by having springsor other devices that have more verticaltravel (referred to as jounce and rebound)when a bump is encountered.

Some frequently encountered sourcesof ride vibration disturbances are:

Road surface roughness

Tire/Wheel/Hub non-uniformity

Driveline component balance or propshaft angularity/phasing

Improper fifth wheel position

Trailer influence

Additionally, longer wheelbase trucksare more likely to have a frame flexing orresonance problem. This simply meansthat as the frame flexes (as all frames doto some degree), the amplitude of flexingand the locations of the high and lowpoints along the frame are more likely tobe objectionable on a long wheelbasechassis. See Figure 8.2.

Whenever a vibration complaint isvoiced on a particular vehicle, the firststep is to eliminate the non-tire sourcesand concentrate on the remaining possible offenders.

Since little can be done about roadroughness, we must concentrate on the

four remaining ones. The driveline, ofcourse, must be balanced, but may alsocause a problem if the angle that the driveshaft forms between the back of thetransmission and the front of the differential is too great. See Figure 8.3.This is encountered most frequently witha short wheelbase vehicle, such as a singledrive axle tractor, designed to pull multiple trailers, or with a truck chassisthat has been shortened. Specific procedures and specifications for checking driveline angularity can befound in truck service manuals for theparticular make/model of the vehiclebeing diagnosed or from driveline equipment manufacturers. Any ride disturbance that can be eliminated by taking the truck out of gear at road speedis probably engine or driveline related.

Figure 8.2 Frame flexing may occur at a point thatcauses great discomfort for the driver.

Figure 8.1 Frame Flexing/Resonance

Frame Flexing/Resonance

Excitation Sources

1. Road Roughness2. Tire/Wheel/Hub3. Driveline Balance4. Fifth Wheel Position5. Trailer Influence

Truck’sDynamicResponse

Cab Vibrations

Driver RideJudgement


60

RideDisturbance

Fifth wheel position and trailer influences can often be altered to determine their effects on a ride vibrationconcern. If the problem seems to berelated to the tires, wheels, or rims orhubs, you should consult your tire company representative.

If ride testing determines that thevibration is likely due to rotating axlecomponents, guidelines for pinpointingtire/wheel/hub related vibration problemsare as follows:

RIDE TEST TIPS• Drive 15-20 miles to warm up tires and

eliminate flat spotting which occurswhen a truck has been sitting idle.

• LOCATION – STEERING WHEEL, SEAT– Steering wheel and/or floor under

the driver’s feet – indicates steer tires– Backslap in seat – indicates rear

assemblies

• TYPE OF DISTURBANCE– Up and down indicates run-out,

balance– Side to side indicates run-out,

balance and possibly irregular wear– Steering wheel shimmy indicates

steer tire dynamic imbalance

RIDE DIAGNOSTICS:TIRES/WHEELS• Identify critical conditions/speed of

the vibration• A vibration that gets worse as speed

increases may be balance related• A vibration that occurs at only one

speed is probably run-out related• A vibration that phases in and out

indicates a problem at more than one wheel position

• Low speed wobble is run-out related –not a balance problem

• A vibration while braking only is probably a brake system issue

BALANCE RELATEDVIBRATION

Balance is most critical on free-rollingwheels (steer and trailer). In general,spin-balancing of drive tires is not needed.It can also be dangerous due to the differential action, which can result invery high rotational speeds at one axleend, and damage to the truck is possible. On-vehicle balancing with a properlycalibrated spin balancer may aid in correcting the vibration problem by balancing that particular tire/ wheel or rim/hub assembly. However, whenplacing that tire and wheel (or rim) on another wheel position or vehicle, it is likely to be out-of-balance. If theproblem is an out-of-balance hub, the ultimate solution is to have the hub balanced.

RUN-OUT RELATEDVIBRATION

For run-out problems, the match-mounting procedure is a complex buteffective method to eliminate, or at leastisolate, the source of the concern. Match-mounting isolates the tire, wheel, andbolt circle of the wheel to determinewhere the problem may be. It can alsodetermine if a combination of variables isresponsible because the tolerances “stack”to create an unacceptable condition.

Since all tires and wheels are likely tohave some run-out and all bolt circles arenot perfectly centered, it is importantthat these factors do not “add up” to createa ride vibration even when individualcomponents are within spec. The acceptedguidelines for run-out of tires, wheels,and wheel bolt circles are shown inFigure 8.4. Vehicles with assemblies and components within these guidelinesshould not have vibration problems dueto tire/wheel factors.

If run-out appears to be a problem, usethe following match-mounting procedureto attempt a correction:

Figure 8.3 Driveline angularity can cause vibration problems.

Driveline Angularity

1 Universal Joint2 Slip Joint3 Shaft

1

2

3 1

Figure 8.4

Runout Guidelines

Radial Lateral

Assembly (on vehicle) .060'' .150''Sensitive Vehicle <.060''Wheel .040''Bolt Circle .020''Tire .060'' .080''


61

RideDisturbance

MEASURINGRADIAL RUN-OUT

Run-out is a measure of deviation from a perfect circle

• Warm up tires• Lift vehicle• Place the dial indicator against the

center of the tread pattern• Turn the wheel slowly and watch the

needle• Find the low spot and zero the gauge• Spin the wheel to check run-out• Mark the high spot• A reading of less than 0.060” (RRO) is

usually good. Sensitive vehicles mayrequire 0.060” or less

REQUIRED TOOLS• Goodyear infoLink,

Ph: 800-755-2772

– Gauge (0.100" per rev) & slidershoe, part no. 220-011-300

– Stand, part no. 220-011-200

1 • Measure radial run-out on the vehicle at the tire centerline

High Spot

Low Spot

2 • Mark the high spot of thetire/wheel assembly and theamount of run-out if over .060”

• Index tires to wheels and wheels tohubs and record assembly position(LF, RF, etc.) on each tire beforeremoval from vehicle

3 • Mount the tire/wheel assembly on a balancer. Check tire “GG”grooves for concentricity with rim flanges on both sides (visual).If not concentric, deflate, breaksidewalls away from rim flanges,lubricate and re-inflate

• Recheck the run-out on the balancer. Compare peak locationsand magnitudes to results from on-vehicle measurement. Mark the high spot of the assembly andindex the tire to wheel as shown

• If RRO on balancer is greater thanon vehicle, hub-to-wheel index isOK. If RRO is less than on vehicle,hub index should be rotated 180°when the assembly is reinstalledon the truck

High SpotAssembly

WheelIndex

AssemblyPosition

Right Front

High SpotAssembly Wheel

Index

HubIndex

RF


62

RideDisturbance

4 • If the assembly RRO is over 0.060”,rotate tire 180° on wheel andremeasure on balancer. If OK, stop.If still excessive, rotate 90° andremeasure. If OK, stop and balance.

5 • If the run-out is still unacceptableand the new high spot is within 6” of the first high spot on the tire,replace the tire. (i.e., If the highspot moves with the tire, the tire’s run-out contribution is higher than the wheel’s contribution)

6 • If above step is OK and the run-outis still unacceptable, and the newhigh spot is within 6” of the wheelindex, replace the wheel. (i.e., If thehigh spot moves with the wheel,the wheel’s run-out contribution ishigher than the tire’s contribution)

7 • Mark final assembly high spot(red) from inside to outside of tire,so it is visible for mounting on thetruck. Erase original marks on thetire (yellow)

• Balance all assemblies beforereplacing on vehicle

• Repeat steps 1-6 for each assemblyon vehicle to optimize overallvehicle ride

8 • Remount tire on the vehicle andmeasure radial run-out. Run-outshould be the same as measured on the balancer. If out of limits,check the stud circle run-out

• When re-installing steer assemblieson vehicle and before tighteninglug nuts, locate the high RRO spotat 12:00 on the hubs

• When re-installing drive dualassemblies on vehicle, install highest RRO spot of one assemblyat 12:00 on the hub. The high spot of RRO on the other assemblyshould be opposite (180° from) the first assembly

• Torque all lug nuts to manufacturer’sspecification and re-ride the truck

For further information, see TMCRecommended Practice RP648 regardingride troubleshooting.

First AssemblyHigh Spot

WheelIndex


New AssemblyHigh Spot

WheelIndex


New AssemblyHigh Spot

WheelIndex

RF

Factors

Affecting Truck

Fuel Economy

S E C T I O N N I N E

63

FactorsAffecting TruckFuel Economy


64


VEHICLE ANDENGINE DESIGNA. Performance Factors

Fuel consumption is a function ofpower required at the wheels and overallengine-accessories-driveline efficiency.

Factors that affect fuel consumptionat steady speeds over level terrain are:

Power Output-Engine-Accessory-Driveline System1. Basic engine characteristics; fuel

consumption vs. RPM and BHP.2. Overall transmission and drive axle

gear ratios.3. Power train loss; frictional losses in

overall gear reduction system.4. Power losses due to fan, alternator,

air-conditioning, power steering, andany other engine-driven accessories.

Power Required - Vehicle and TiresThe horsepower required for a vehicle

to sustain a given speed is a function ofthe vehicle’s total drag. The greater thedrag, the more horsepower is required.The total vehicle drag can be brokeninto two main components; aerodynamicdrag and tire drag. Factors affectingthese components are:

FactorsInfluencing Drag

Aerodynamic – Vehicle speedVehicle Frontal areaVehicle Shape

Tire – Vehicle Gross WeightTire Rolling Resistance

Both aerodynamic drag and tire dragare influenced by vehicle speed. It isimportant, though, to note that speedhas a much greater affect on aerodynamicdrag than on tire drag, Figure 1.

Gains in fuel economy can be madeby either optimizing or reducing some of the factors affecting drag.

B. Type of VehicleThe type of vehicle affects aerodynamic

drag through its size (frontal area) andshape. The following illustration showstwo tractor-trailer combinations which,as a result of their shorter height (h2 and h3), have smaller frontal areasthan the standard van-type trailer.

Trailer shape has a large impact on theaerodynamic drag of the tractor-trailercombination. Some examples of trailers thathave lower aerodynamic drag shapes are:

FIGURE 1

Vehicle Speedvs.

Aerodynamic Drag and Tire Drag

Vehicle Speed

Dra

g Fo

rce

30 40 50 60 70 80

Tire Drag

Aerodynamic Drag

Where: h1>h2<h3 Frontal Area = FA = (h) x (w) Where: h = Height; w = Width

h1

h2

h3


65


Drop frame trailers – Less “Open Air”space under the trailer. This also createsless airflow disturbance in crosswindconditions and thereby reduces theamount of drag.

Sharp Vertical Edge

Rounded Vertical Edge – Maintains“Attached” airflow along the trailersides, which reduces drag.

Airflow

Airflow

Airflow

Airflow


66


C. Use of Aerodynamic Drag Reduction Devices

With van-type trailers, certain add-ondevices are capable of reducing a vehicle’saerodynamic drag. These devices helpmaintain an “attached” airflow along thetrailer sides. Again, an increase in dragoccurs when the airflow becomes “detached.”

The favorable impact of roof fairingsis maximized when the vehicle is operatingin a “head-on” wind condition as shownabove. The effectiveness of a roof fairingis reduced when the vehicle encounters a“crosswind” (yaw wind) condition. Also,if the trailer height is lower than the topof the fairing, as in the case of a flat-bedtrailer, the fairing increases drag becauseit increases the vehicle’s frontal area. Useof a “roof shield” is less effective than a“roof fairing” because it doesn’t channelthe wind at the sides. Therefore, a “rooffairing” is preferred.

Vertical gap seal devices reduce dragby preventing the airflow from enteringthe “open air” space between the tractorand trailer. Unlike the roof fairing, theimpact of this device is maximized when the vehicle is operating in a yaw wind condition.

D. Engine and DrivelineCharacteristics

The use of wide torque band lowRPM engines and wide-step top geartransmissions, combined with proper rear axle ratios, leads to fuel economyimprovement when operated in thespeed and RPM ranges recommended by engine and vehicle manufacturers.

Note that a change in the overalldiameter of the drive axle tires can effectively alter the rear axle ratio andcould adversely affect fuel economy. Thedetermination whether a drive tire changeproduces an increase or decrease in fueleconomy depends on how much and inwhich direction engine RPMs are changed.

Side Gap Seal

Vertical Gap Seal

Airflow

Also of importance is the amount of gapbetween the back of the tractor cab andthe front of the trailer. The larger the gap,the greater the disruption to the airflowand the resulting drag. This becomeseven more important when encounteringcrosswind conditions (yaw wind). A ruleof thumb is for every 10'' over a 30'' gapthere is about a 1/10 drop in MPG.

Long Wheelbase Tractor

Yaw Wind Condition

Airflow

Gap

Gap


67


VEHICLE OPERATIONThe effect of tire overall diameter on

fuel consumption can be illustrated usingan engine fuel map, Figure 2. This is anexample of a typical part load brake specificfuel consumption (BSFC) engine map. Itshows lines of constant BSFC as a functionof engine BHP output (vertical axis) andengine RPM (horizontal axis).

A smaller diameter drive axle tireresults in an increase in engine cruiseRPMs, from point A to B. At point B theengine is consuming more fuel for thesame BHP output.

Proper drive train component matchingcan provide the most fuel efficient RPM/ground speed combination to maximizefuel economy. Engine RPMs can bedetermined using the following formula:

Engine RPM=V x TR x AR x (Tire RPM)60

Where:V = Vehicle Speed (mph)

TR = Transmission Ratio @Top Gear (e.g. 1.0 for Direct Drive)

AR = Rear Axle Ratio (e.g. 3.70)Tire RPM = Tire Revs Per Mile

(obtained from Goodyear’sEngineering Data Book or www.goodyear.com/truck)

Lines Of Constant BSFC

Increasing Fuel Consum

ption

Engine Speed - RPM

Engi

ne

Ou

tpu

t -

BP

H

600 900 1200 1500 1800 1200

360

330

300

270

240

210

180

150

120

90

60

30

A B

A = Cruise Point @ 0% Grade, 80,000 Lbs. GCW

FIGURE 2

A. GeneralConsider a typical tractor and van

combination operating at 80,000 lb.gross combination weight and at 55 MPHon a level highway. No aerodynamicdrag reduction devices are used oneither the tractor or the trailer. Usingbias ply tires in all wheel positions, theapproximate distribution of horsepowerrequirements is as follows:

HPItem Requirement Percent

Aerodynamic Drag 104 40

Tire Roll Resistance 97 38

Driveline Losses 36 14

Engine Accessories 20 8257 100

In this example, the horsepowerrequired to overcome bias ply tire rollingresistance is essentially the same as thatrequired to counteract aerodynamic drag.The total horsepower requirement canbe lowered with the use of radial ply tires.

Because radial ply tires have lowerrolling resistance than bias ply tires, tire horsepower requirements are lower.As a result, fuel economy is improved.And as the proportion of tire horsepowerrequirement on a vehicle increases, thegain in fuel economy due to using radialtruck tires increases. Some examples of tire horsepower requirements as apercentage of total vehicle horsepowerrequirements are given in Figure 3.

At lower Gross Combination Weights(at the same speed), the horsepowerrequired to overcome the tire rollingresistance is a smaller portion of thetotal brake horsepower required (BHP).This is also true as speed is increased (atthe same GCW). As the vehicle’s aero-dynamics are improved, as in the case ofa tractor pulling a tanker trailer ratherthan a van trailer, the BHP required toovercome aerodynamic drag is reduced.This has the effect of increasing thepercent contribution of tire rolling

resistance to the total BHP required. Inthis case, reducing tire rolling resistanceby switching to radials has a greaterimpact on reducing the total BHPrequired.

FIGURE 3Tractor-Trailer Horsepower Requirements

By Component

Engi

ne

Bra

ke H

ors

epo

wer

Req

uir

ed

400

300

200

100

0

Van Trailer

257237

179 172

357334

55 MPH

Bias RadGCW=78,500

Bias RadGCW=25,000

Bias RadGCW=78,500

65 MPH

Tanker Trailer

Key: HP Required to Overcome –

��

��

��

��

��

��

Engi

ne

Bra

ke H

ors

epo

wer

Req

uir

ed

400

300

200

100

0

55 MPH

Bias RadGCW=78,500

Bias RadGCW=25,000

Bias RadGCW=78,500

65 MPH

��

Aerodynamic Drag

Tire Rolling Resistance

Driveline Losses��Accessory LossesAccessory Losses

��

��

��

��

��

��

38%

211

46%

134

282260

23%

128

20%

41% 37%

192

42%

34%

17% 15%

32%28%

Source: Goodyear Maintenance CalculationsSource: Mack Truck Engineering, Allentown, PA, Oct. 1992


68


B. Type of HaulThe ideal type of haul for maximum

fuel economy consists of long distanceruns at steady moderate speed with aminimum of stop-and-go driving andwith a minimum of turning. Shorter runsinvolve more braking, acceleration andturning. The engine and tires operate at less than optimum conditions. Fueleconomy tends to be reduced. In somecases of stop-and-go driving, tires maybe operating “cold” part of the timewithout sufficient continuous drivingtime for adequate warm-up. A curve oftire rolling resistance vs. warm-up time as obtained from a laboratory test isgiven in Figure 4.

A 1975 study by the U.S. Departmentof Transportation and the U.S. Environmental Protection Agencya

concluded that the type of haul (local,short-haul, or long-haul trips) has a strongeffect on fuel economy improvementattributable to radial tires.

The increased stop-and-go driving of the shorter haul reduces the fueleconomy gain due to radials. The results of the study are given below:

Fuel Economy Improvement Due ToRadial Tires Versus Driving Mode

Fuel EconomyDriving Mode ImprovementLocal 3 to 5%Short-Haul 4 to 8%Long-Haul 5 to 9%

aInteragency Study of Post-1980 Goals for Commercial Motor Vehicles; Revised Executive Summary, November 1976.U.S. Department of Transportation and U.S. EnvironmentalProtection Agency.

C. Vehicle SpeedAs vehicle speed is increased,

horsepower requirements to overcome theaerodynamic drag increase rapidly. Thereis also an increase in the horsepowerrequired to overcome increasing tirerolling resistance, though this occurs ata lower rate. The sum total horsepowerrequirement for a tractor-trailer vehicleincreases along a curve which has a continually steeper slope as speed isincreased. For example, Figure 5 showsthat the total horsepower requirement at65 MPH is 40 percent greater than at 55 MPH for the typical tractor and van-type trailer. As a result, fuel economy willfundamentally decrease as operatingspeed is increased from 55 to 65 MPH.

A calculated curve of the percent differencein MPG versus speed is shown in Figure 6.A reduction in MPG of about eight percent was found for every 5 MPHincrease in vehicle speed over 55 MPH.For 65 MPH, this would equal close to a mile-per-gallon loss in fuel economy.

D. Vehicle GrossCombination Weight

As gross combination weight isincreased, tire rolling resistance increases,and vehicle miles per gallon decreases,assuming speed is maintained constant.

To verify this point, fuel economytests were conducted at the GoodyearSan Angelo Proving Grounds onGoodyear over-the-road tractor-trailers.Unisteel radial tires were compared to

Super Hi-Miler and Custom Cross Ribbias ply tires on the same vehicles todetermine relative miles per gallon.a

Figure 7 shows the results of the testsalong with calculated curves passingthrough the test points. The effect ofvehicle gross combination weight on milesper gallon is shown. Note that as truckgross weight was increased, miles pergallon decreased with both the Unisteelradial tire and the bias ply tire; however,the Unisteel tire gave proportionatelygreater improvement in fuel economy as truck gross weight was increased.

Tests were run at the San AngeloProving Groundsa to determine the effectof Gross Combination Weight on vehiclemiles per gallon, comparing 11R22.5Unisteel radial to 11-22.5 bias ply tires at60 MPH. Figure 8 shows that at a GCW of

FIGURE 6Vehicle Speed

vs.Percent Change in MPG & BHP

Vehicle Speed (MPH)

% D

iffe

ren

ce i

n M

PG

30

50

40

3020

10

0

-10

-20-30

-40

-50

40 50 55 60 70

VehicleHorsepower Required

Miles-Per-Gallon

FIGURE 5Calculated

Horsepower Requirements Tractor, 13.5 Ft. High Van Trailer

vs. Vehicle Speed

11R22.5 Radial Tires GCW=78,500 Lb.

Truck Speed–MPH

Ho

rsep

ow

er R

equ

ired

200

30

100

40

200

50 60 70

300

400

AccessoriesDriveline Losses

Tire Roll. Resist.

Aero. Drag

Total Vehicle Requirements

A rule of thumb. Increase of 10 mph = decrease of 1 mpg.

FIGURE 4Laboratory Tests Truck Tires

Rolling Resistancevs.

Warm-Up Time With Capped Air

75 PSICold

95 PSICold

95 PSI Hot

110 PSI Hot

11-22.5 Bias PlyLR-F, 4760 Lb. Load

11R22.5 RadialLR-G, 5300 Lb. Load

Elapsed Time–Minutes

Un

corr

ecte

d R

oll

ing

Res

ista

nce

–Lb

.

0 1536

30

38

45

40

60 75 90 105

42444648505254

Source: Goodyear Maintenance Calculations

Source: Goodyear Fuel Economy Model Prediction


69


78,700 lb., the measured MPG advantageof the radial tire was 6.7 percent, while ata GCW of 46,000 lb., the correspondingvalue dropped to 1.6 percent. Thismeasured reduction in the miles per gallonadvantage of radial tires at the lighterload was more severe than theory wouldindicate. Calculations show that the 6.7percent advantage should drop to about3.5 percent at the lighter load.aThe Effects of Goodyear Unisteel Radial Ply Tires on FuelEconomy. Goodyear Tire & Rubber Company Booklet dated 2/77.

E. DriverDriver operating procedures are

important factors in achieving maximumvehicle fuel economy. The potentialbenefits of lower vehicle aerodynamicdrag, lower tire rolling resistance, andmore efficient engines can be offset oreven negated by a driver running at ahigher speed.

General rules for the driver to follow are:b

• Keep accurate records of fuel used,routes taken and loads carried so

The test data above confirms that thefuel economy advantage of radial trucktires over bial ply tires increases with heavier vehicle Gross CombinationWeights.aTire Parameter Effects of Truck Fuel Economy. R.E. Knight, The Goodyear Tire & Rubber Company. SAE Technical Paper791043, November 1979.b“17 Tricks to Save Fuel and Save $$$$”; Pamphlet DOTHS804 547, June 1979.

you know if you are making anyimprovements.

• Try progressive shifting, don’t runagainst the governor on every shiftand stay 200-300 RPM below thegovernor at cruise (See Figure 9).

• Stay in as high a gear as possible. You can’t lug today’s engines if you canmaintain speed in any gear. Keep RPMlow: below the governor but abovethe minimum RPM recommended by the engine manufacturer.

• Eliminate unnecessary idling. Shortenwarm-up and cool-down times to the minimum recommended by theengine manufacturer. Don’t leave theengine idling while you eat lunch or have coffee.

• Drive defensively.• Cut down top speed. Each MPH over

55 costs you 2.2% in fuel costs!• Watch the fueling operation. If you

top the tank that valuable liquid couldspill or overflow later when you’reparked in the sun.

• Carry as big a load as you can. Run as few empty miles as you can.

• Anticipate traffic conditions.Accelerate and decelerate smoothly.

Tire care can also affect fuel economy.The most important thing a driver cando is to check inflation pressure oftenwith a calibrated tire gauge and makesure that tire pressure is maintained at arecommended high value. (See Figure 14for effects of inflation pressure on fuel economy.)

FIGURE 7Miles Per Gallon vs. Truck Gross Weight

V=55 MPH

WeightEmpty

Bias Tires

RadialTires

San Angelo Tests

12th Gear, G.R.=1.00

Texas Shuttle

10.00R20/10.00-20 Size Tires13.5 Ft. High VanCummins NTC 350 Engine Test Points

Gross Combination Weight (Thousands of Pounds)

Mil

es P

er G

allo

n

202.0

3.0

4.0

5.0

6.0

7.0

40 60 80 100 120 140

˚

FIGURE 9Progressive Shifting

GovernedRPM

Miles Per Hour0 10 20 30 40 50 60

IdleRPM

Engi

ne

RP

M

FIGURE 8Effect of Gross Combination Weight (GCW)

on MPG Advantage of Radial TiresPercent Increase in

MPG Radial/BiasTest DataGCW

78,70046,000

6.71.6

6.7*3.5

Calculated

*Assumed Same Value As Test Data

Source: Tricks to Save Fuel and Save $$$, DOT Pamphlet HS 804547, June, 1978

Source: Goodyear Testing Data

Source: Goodyear CFG Tests and Mathematical Calculations

Source: Tricks to Save Fuel and Save $$$, DOT Pamphlet HS 804547, June, 1978


70


A. Tire Rolling ResistanceThe primary cause of tire rolling

resistance is the hysteresis of the tirematerials/structure, its internal friction,which occurs as the tire flexes when thevehicle moves. Tire rolling resistanceacts in a direction opposite the directionof travel and is a function of both theapplied load and the tire’s inflation pressure (See Figure 10).

To accurately determine a tire’s rollingresistance, a controlled laboratory test isconducted. One method employed, is torun the tire against an electrically driven67'' diameter flywheel. A torque cell isused to measure the amount of torquerequired to maintain a set test speed at aprescribed test load condition. With thistorque value, additional adjustments areperformed to arrive at the tire’s rollingresistance. The laboratory test providesa procedure where environmental influences (such as ambient temperature,wind, and road surface texture) can beeither controlled or eliminated. Also,strict limits are placed on allowable variations in test speed, slip angle, appliedload, and specified test inflation. Thesecontrols insure test repeatability andallow the accurate assessment of a tire’strue rolling resistance.

Tire rolling resistance is commonlydefined in two ways:a. Pounds resistance per 1000 pounds

of loadb. Pounds resistance per pound load

(rolling resistance coefficient)

B. Types of TiresRadial Ply vs. Bias Ply

The significant differences betweenthese two tires are the angle of body pliesand the presence of belts. Figure 11 showsthe basic structural differences. Notethat the Unisteel radial tire incorporatesa single radial ply and a multiple beltsystem. The bias ply tire has six to eightdiagonally oriented plies and no beltsystem (although the bias ply tire usuallyhas two fabric “breakers” under the tread with same angle as the plies). Onesignificant advantage of the Unisteel tire is the relatively low internal frictioncompared to that in a tire using bias ply construction.

The lower internal friction of theUnisteel tire helps minimize operatingtemperatures and rolling resistance,major causes of tire wear and excess fuel consumption.

Unisteel radial ply tires can providefuel savings of six percent and morecompared to bias ply tires in over-the-roadtractor-trailer applications.

Tubeless vs. Tube Type Laboratory rolling resistance tests

indicate that by changing from a 10.00R20tube type tire to an equivalent 11R22.5tubeless tire in all wheel positions, again of about 2% in miles per gallon canbe achieved at 80,000 Ib. GCW.

Larger Diameter Tires Laboratory tests indicate that, under

the same load and inflation condition,larger diameter tires produce slightlylower rolling resistance, as in the case ofan 11R22.5 versus an 11R24.5. This canproduce an improvement in fuel economycoupled with the reduction in engine RPMsdue to the larger overall tire diameter ondrive axles. (See Section 1-D for theeffect of engine RPMs on MPG.)

TIRE SELECTIONAND MAINTENANCE

Unisteel Radial Ply Bias Ply

FIGURE 11

Radial Ply vs. Bias Ply Construction

FIGURE 10

Load

Direction of Travel

Tire Rolling

Resistance(Tire Drag)


71


Wide Base Super Single TiresGoodyear Proving Grounds tests showthat a fully-loaded tractor-van trailerusing Goodyear Super Single Unisteel15R22.5 tires instead of dual steel radial11R22.5 tires on tractor drives and ontrailer, obtains an average increase ofseven to eight percent in MPG.

Commercial fleet testing using loadedtractor-tanker trailers showed a nine percent gain in measured MPG throughthe use of wide base single 15R22.5 steel

radial tires instead of 11R22.5 steel radial tires in the dual positions. A comparison of the super single versusduals configuration is shown in Figure 12.

Retreaded Radial Tires Goodyear laboratory tests show that

the rolling resistance of newly retreadedradial tires is, on the average, the sameas radial tires with the full original tread.There are some differences due to typeof retread, but all newly retreaded radialtires tested exhibited considerably lowerrolling resistance than new bias ply tires.

Radial Tires on Trailer Axles The type of tire used on an axle has

a direct impact on the vehicle’s fueleconomy. Testing has shown that usingradial tires on trailer axles produces overhalf of the total improvement obtainedwhen converting a vehicle from all biasto all radial. Figure 13 details the totalpercent gain in MPG by switching frombias to radial tires and, of this total gain,

the percentage due to steer, drive, andtrailer tires. For maximum fuel economyas well as for best handling, radial tiresshould be used in all positions of a tractor-trailer unit. Using radial tires especiallydesigned for trailer application will alsoprovide an additional improvement infuel economy. For example, the radiallow profile G114 offers approximately a10 percent lower rolling resistance thanthe G159 low profile.

For a vehicle already equipped withradial tires and being switched to anothertype of radial, the percent contributionby axle to fuel economy will differ from that shown in Figure 13. A rule ofthumb for this case is that the front tirescontribute about 14 percent of the total,the drive tires about 39 percent, and thetrailer tires about 47 percent. It should benoted that the actual percent contributionmay differ from the above due to theeffects of vehicle loading, tire inflation,and tire type.

FIGURE 13

% Difference in MPGBias Tires vs. Radial Tires

-Control-All Bias

Wide Base Single

Dual Assembly

Bias

Bias

Bias

Radial

Radial

Radial

Bias

Bias

Radial

Bias

Radial

Bias

Radial

Bias

Bias

All Radial

Radial-Fronts

Radial-Trailers

Radial-Drives

% Gain % ofin MPG “All Radial”

vs. Control Gain in MPGRadial Fronts 1.0% 17%Radial Drives 1.5% 25%Radial Trailers 3.4% 58%

FIGURE 12

Radial Wide Base Single Tire vs. Radial Dual Tire Assembly

% Gain in MPG vs. Control = 5.9%

Source: Goodyear CPG Test


72


C. Tire Maintenance Inflation Pressure

Laboratory tests were conducted todetermine the effect of inflation pressureon the rolling resistance of the 295/75R22.5G159, G167, and G114 radial truck tires.This laboratory data was used to calculatethe corresponding effect of inflationpressure on the fuel consumption of atypical tractor-trailer at 55 MPH on alevel highway. The effect of inflationpressure on fuel consumption by axleposition was also studied. The results are shown on Figure 14.

A dual tire load of 4250 Ibs./tire anda steer tire load of 5390 Ibs./tire wereselected along with a specified inflationpressure of 100 PSI for all tires. Figure 14shows the percent loss in fuel economydue to the lower inflation pressures.

Operating a loaded tractor-trailerwith inflation pressures of all tires as lowas 70 PSI results in a calculated reductionin MPG of about five percent. The largestcontributor to this loss in MPG is thereduction in inflation pressure of thetrailer tires — it alone accounts for halfthe loss. Varying only the steer tire

inflation pressures results in the smallestpercent change in MPG.

It must be noted that the tractor-trailer load affects the percent reductionin MPG due to underinflation. Thelighter the GCW, the smaller the percentloss in MPG (for the same reduction intire inflation).

FIGURE 14

Radial Truck Tire Inflationvs.

Percent Change in MPG

Tire Inflation Varied:

Tire Inflation (psi)

% D

iffe

ren

ce i

n M

PG

GCW =78,780 lbs.V = 55 MPH

Front Axle

Drive Axles

Trailer Axles

Front, Drive andTrailer Axles

60

5.04.54.03.53.02.52.01.51.00.50.0

-0.5-1.0-1.5-2.0-2.5-3.0-3.5-4.0-4.5-5.0-5.5-6.0

65 70 75 80 85 90 95 100 105 110 115 120

A good rule of thumb is that every10 PSI reduction in overall tireinflation results in about a one percent reduction in MPG.

Source: Goodyear Fuel Economy Model Predictions


73


Alignment For optimum fuel economy on a tractor-

trailer, and also for optimum tire wear,tandem drive axles and tandem traileraxles should be maintained in properalignment. Alignment of the vehicle’standem axles should be considered asimportant as the alignment of the steeraxle tires. The importance of this is notonly reflected in the loss of MPG due to the increase in tire rolling resistance,but also in the increase in tire wear as a result of the greater amount of side-scuffing. The effects of drive axle andtrailer axle alignment is even greater due to the number of tires involved:eight vs. two.

Figure 15 illustrates the results of a

Goodyear fuel economy test program runat TRC of Ohio in 1986. These evaluationswere Type II tests conducted to SAE J1376standards. Tests #2 and #3 with steer axletoe-in of 1/4- inch, along with misalignedtandem axles of 1/2-inch total (differencein fore and aft distance between axlecenter lines, from one side of the vehicleto the other), did not result in a significantloss in MPG versus the specificationaligned tractor-trailer. The percentincrease in tire rolling resistance due tothe slip angles (under .2°) generated bythese misalignment conditions is small.What is of greater significance is theloss in tire treadwear life.

Increasing the steer tire toe-in to 3/8-inch and the tandem axle misalignment

to 1-inch in test #4 does produce a lossin MPG which is significant.

The greatest loss in MPG was produced in test #5 where a “dog-tracking”condition was simulated. The trailer tandem axles were misaligned by 1.5-inch though the axles were parallel toone another. The loss in fuel economywas about two percent in addition toincreased tread loss.

Treadwear As the tread is worn down, tire

rolling resistance decreases and vehiclefuel economy increases for both radialand bias ply tires. Proving Grounds testsshowed about a one percent increase in miles per gallon for radial tires withtread approximately 30 percent worn.a

Laboratory tests show about a 10 percentdecrease in rolling resistance for bothradial and bias ply tires with tread halfworn, and a 20 percent decrease for afully worn tire. (See Figure 16.) aTire Parameter Effects on Truck Fuel Economy by R. E.Knight, The Goodyear Tire and Rubber Co. SAE TechnicalPaper No. 791043, November 1979.

FIGURE 15

Tractor-Trailer Alignment Effects On Fuel Economy

FIGURE 16Effect of Treadwear on Truck

Tire Rolling ResistanceLaboratory Data

10.00R20/11R22.5 Sizes At Approx. Rated Dual Load And Inflation, LR-F

‘‘Tips For Truckers’’ FEA/DOT/EPA Document GPO 910-940 Calspan Rep. DOT-TST-78-1Goodyear TestCalculation, Based On Goodyear FuelEconomy Test

Bias Ply

Radial ply

Percent Treadwear

Per

cen

t R

oll

ing

Res

ista

nce

00

20

20

40

40

60

60

80

80

100

100

ALIGNMENTSteer Tire.

Toe-In: 0'' 1/4'' 1/4'' 3/8'' 3/8''Drive Axle.

Non-Parallel: 0'' 0'' 1/2'' 1'' 1''Trailer Axle.

Non-Parallel: 0'' 1/2'' 1/2'' 1'' 0''

*Non-Perpendicular to Frame, 1-1/2''% Improvementin Fuel Economy: -0.6 -0.8 -1.7 -2.2

Test #1 Test#2 Test#3 Test #4 Test #5

Source: Goodyear Fuel Tests at TRC of Ohio, 1986


74


ENVIRONMENTALCONDITIONSA. General

Conditions external to the vehiclecan have a strong influence on the fueleconomy achieved by a given driver andtractor-trailer/tire combination. Some ofthe greater influences are exerted by:

Winds Road Surface Ambient Temperature Terrain

B. Winds Headwinds and crosswinds reduce

truck fuel economy by increasing truckairspeed and/or yaw angle, thus increasingaerodynamic drag. To avoid excessivefuel consumption in sustained strongheadwinds, a decrease in truck highwayspeed is indicated.

Crosswinds also tend to diminish theeffectiveness of aerodynamic drag-reducingdevices such as cabmounted flow deflectors.Tailwinds are generally beneficial inincreasing fuel economy because of thereduced airspeed for a given highwayspeed. However, if the driver takesadvantage of the tailwind and increaseshis highway speed, the fuel economygains will be reduced or lost completely.

C. Road Surface The type of road surface can affect

tire rolling resistance. Smooth-texturedhighway surfaces provide the lowestrolling resistance, while coarse-texturedsurfaces give the highest tire rolling resist-ance and the lowest fuel economy.

In a test,b it was found that a coarsechip-and-seal pavement surface gave anincrease in passenger tire rolling resistanceof 33 percent over that obtained on atypical new concrete highway surface.Relative rankings of the test surfaces were:

Relative Rolling

Surface Resistance %Polished Concrete 88New Concrete 100 Rolled Asphalt

(rounded aggregate) 101 Rolled Asphalt (medium

coarse aggregate) 104 Rolled Asphalt

(coarse aggregate) 108 Sealed Coated Asphalt

(very coarse) 133

Another study on passenger tiresc

investigated the effect of road roughness(not surface texture) on rolling lossesand concluded:1. Road roughness increases both

rolling and aerodynamic losses (thelatter due to vehicle pitching action).

2. Road roughness significantly increasesvehicle rolling losses due to energydissipation in the tires and suspension.

3. Tests on rough roads led to increasesin rolling losses as large as 20 percent,in addition to introducing increasesin aerodynamic drag.

Truck fuel economy may be expectedto be influenced in a manner similar tothat of passenger cars; by the surfacecondition of the roadways traveled andby the type of materials used in thepavement—especially in asphalt/ crushedstone mixes. Tire treadwear as well asvehicle fuel economy may be influencedby the particular area of the countrybeing traversed, depending upon thesharpness and hardness of the localcrushed stone used in asphaltic concreteroad pavement mixes.

bL. W. DeRAAD “THE INFLUENCE OF ROAD SURFACETEXTURE ON TIRE ROLLING RESISTANCE”, SAETECHNICAL PAPER 780257 PRESENTED AT THECONGRESS AND EXPOSITION, COBO HALL,DETROIT, FEBRUARY 27 - MARCH 3, 1978.

cSteven A. Velinsky and Robert A. White, “Increased VehicleEnergy Dissipation Due to Changes in Road Roughness withEmphasis on Rolling Losses.” SAE Technical Paper 790653Presented at Passenger Car Meeting, Dearborn, Michigan, June 11-15, 1979.


75


D. Ambient TemperatureHigh ambient temperatures reduce

tire rolling resistance. High temperaturesalso reduce atmospheric density, resultingin lower aerodynamic drag. However, fueleconomy performance of non-turbochargeddiesel engines may be adversely affectedby high ambient temperatures, and thiswould tend to negate some of the gainsresulting from lower tire drag and loweraerodynamic drag.

Cold weather operation has an opposite effect: tire drag and aerodynamicdrag increase at the lower ambient temperatures. The greater thermal efficiency of internal combustion enginesat low ambient temperature is usuallycancelled by longer warm-up times andlonger idling times to maintain cab temperatures during stopover periods.Thus, wintertime fuel economy is generallylower than that obtained in the summer.

E. Terrain 1. Grades

Most proving grounds fuel economytesting is done on level terrain, and mostsimplified calculations relating varioustruck and tire parameters to truck fueleconomy also assume level terrain.

The effect of traveling up a grade is very significant in terms of reducingtruck fuel economy. Assuming a one percent grade and an 80,000 pound tractor-trailer, there will be a rearwardforce exerted by gravity of 80,000pounds x .01 = 800 pounds.

Proving grounds tests over a measuredmile on a road with a 0.1 percent gradeconsistently showed eight to ten percentlower miles per gallon, comparing goinguphill to the west with going downhillto the east. This difference was obtainedusing a typical tractor-trailer at 55 MPHand at a gross combination weight of78,500 pounds.

Traveling on a downhill grade improvesfuel economy and in hilly country helpsto counteract the losses in fuel economysustained by traveling upgrade.

2. Altitude As altitude increases, air density and

atmospheric pressure decrease. At 5,000ft. altitude, for example, air density in astandard atmosphere is 14 percent lessthan at sea level. This percent reductionin air density also applies to reduction inaerodynamic drag, all else being equal.

Tire rolling resistance is not affectedby altitude, per se, unless cold inflationpressure is set at lower altitudes and notchanged as altitude of operation increasesduring the course of the trip. For example,a tire with a gauge cold inflation pressureof 100 PSI at sea level, if taken to 5,000 ft.altitude at the same ambient temperature,would have a gauge cold inflation pressureof about 103 PSI. This added inflationwould tend to reduce tire rolling resistance.

Altitude effect on engine fuel economyperformance depends on the particularengine design and whether or not it issupercharged or tuned for high-altitudeoperation.

MPG vs. Average Daily Ambient Air Temperature

Average Daily Ambient Air Temperature

MP

G

0 20 40

5.4

5.2

5

4.8

4.6

4.4

4.260 80 100

**

**

*

**

***

*

** ****

*********** * *

******

***** * * ***


76


TIRE DESCRIPTIONAND SPECIFICATIONS

• Static Loaded Radius (SLR)—The distance from the road surface to the horizontal centerline of the wheel,under dual load

• Minimum Dual Spacing—The minimumdimension recommended from rimcenterline to rim centerline for optimumperformance of a dual wheel installation

• Loaded Section (LS)—The width ofthe loaded cross-section

Tire profile or cross-sectional shape isdescribed by aspect ratio (AR): the ratioof section height (SH) to section width(SW) for a specified rim width. For agiven tire size, the aspect ratio for aGoodyear radial truck tire is the same as for a bias ply truck tire.

Safety WarningSerious Injury May Result From:• Tire failure due to underinflation/

overloading/misapplication—followtire placard instructions in vehicle.Check inflation pressure frequentlywith accurate gauge.

• Explosion of tire/rim assembly due toimproper mounting—only speciallytrained persons should mount tires.When mounting tire, use safety cageand clip-on extension air hose to inflate.

Cross-Sectional View of Typical Tire

Goodyear Unisteel Low Profile Radial

7. Chafer—A layer of hard rubber thatresists rim chafing.

8. Radial Ply—The radial ply, togetherwith the belt plies, withstands theburst loads of the tire under operatingpressure. The ply must transmit allload, braking, and steering forcesbetween the wheel and the tire tread.

9. GG Ring—Used as reference forproper seating of bead area on rim.

10. Bead Core—Made of a continuoushigh-tensile wire wound to form ahigh-strength unit. The bead core isthe major structural element in theplane of tire rotation and maintainsthe required tire diameter on the rim.

Terms Used To Describe Tire/Rim Combination• Outside Diameter (OD)—The

unloaded diameter of the tire/rim combination

• Section Width (SW)—The maximumwidth of the tire section, excludingany lettering or decoration

• Section Height (SH)—The distancefrom the rim to the maximum heightof the tire at the centerline

1. Tread—This rubber provides theinterface between the tire structureand the road. Primary purpose is toprovide traction and wear.

2. Belts—Steel cord belt plies providestrength to the tire, stabilize thetread, and protect the air chamberfrom punctures.

3. Stabilizer Ply—A ply laid over the radial ply turnup outside of thebead and under the rubber chaferthat reinforces and stabilizes thebead-to-sidewall transition zone.

4. Sidewall—The sidewall rubber mustwithstand flexure and weatheringwhile providing protection for the ply.

5. Liner—Layers of rubber in tubelesstires especially compounded forresistance to air diffusion. The linerin the tubeless tire replaces theinnertube of the tube-type tire.

6. Apexes—Rubber pieces with selected characteristics are used tofill in the bead and lower sidewallarea and provide a smooth transitionfrom the stiff bead area to the flexible sidewall.

1

3

5

6

4

8

9

2

7

10

Section

Width (SW)

Static LoadedRadius (SLR)

FlangeHeight

Rim Width

OutsideDiameter (OD)

Section Height (SH)

Minimum Dual Spacing

Loaded Section(LS)


77


SUMMARYThe average fuel costs of a given

trucking fleet are related to two factors:

• Average fleet miles per gallon• Average fuel cost per gallon

While it seems little can be done atthe present time to reduce fuel cost pergallon, there are steps that can be takento increase average fleet miles per gallon.

The miles per gallon achieved by agiven truck depends on many factors,the major ones being:

• Vehicle, Engine and Accessory Designand Maintenance

• Vehicle Operation• Tire Selection and Maintenance• Environmental Conditions

Major fuel-saving steps to apply totrucking operations are:

1. Use fuel-efficient high torque rise,lower RPM engines.

2. Use engine accessories with reducedhorsepower requirements, such asclutch fans, synthetic lubricants, etc.

3. Use aerodynamic drag reductiondevices such as flow deflectors androunded trailer fronts and corners on tractors pulling van-type trailers.Cover open-topped trailers with atightly-stretched tarpaulin.

4. Use radial tires in all wheel positions,trailer as well as tractor.

5. For best fuel economy, do not allowradial tires to operate below 95 PSIcold inflation pressure.

6. Do not exceed the tire’s rated speed; operate truck fully loaded as much of the time as possible to increaseton-miles per gallon.


78


APPENDIXFuel Economy Test Procedures

There are three fuel economy testprocedures which have been developedby the Society of Automotive Engineers(SAE) and which are currently beingused by vehicle manufacturers, tire manufacturers, and by some fleet owners.These offer a standardized method toevaluate either a complete vehicle or acomponent. Consideration has been givento the effects of environmental conditions(such as those described in Section 4),and their effect on fuel economy results.This is accomplished by requiring theuse of a control vehicle which is runsimultaneously with the test vehicle.Environmental conditions should affectboth vehicles in a similar manner so thatfor a set of tests, the ratio of either thefuel used or the MPG of the test andcontrol vehicles should be relatively constant even though the actual valuesof either the fuel used or the MPG mayvary from test to test.

A brief description of each procedureis listed along with some of their importantrequirements.

A. SAE Type IThe SAE Type I procedure is best used

to evaluate a component which can beeasily switched from one vehicle to another.

The procedure requires two vehiclesof the same specification; these are runsimultaneously and are identified as vehicles “A” and “B.”

The minimum mileage required forone complete test cycle is 200 miles.This is composed of a 100 mile roundtrip with the test component on vehicle“B” and then another 100 mile round tripwith the test component on vehicle “A.”Since a round trip must start and finishat the same location, the minimumlength of the outbound and inbound test leg is 50 miles.

On the outbound test leg vehicle “A”leads vehicle “B” (approximately 200 -250 yard separation). At a point halfwaythrough this test leg (approx. 25 miles)vehicle “A” slows down to allow vehicle“B” to take the lead. At the completion ofthe outbound leg, fuel tanks are weighedor fuel meter readings are recorded. Onthe inbound test leg, vehicle “B” leads “A”(same separation distance as outboundleg). Also at a point halfway through the test leg “B” slows down to allow “A” totake the lead. Upon completion, fuel isweighed or meters recorded. The testcomponent is then switched betweenvehicles and another round trip is made.

The amount of fuel used by vehicles“A” and “B” when they are operating with the test component is compared tothat used by both vehicles without thetest component.Test speed — as requiredVehicle loads — within five percent

of each otherVehicle warm-up — representative of fleet

operation or not lessthan 45 minutes attest speed

B. SAE Type II The SAE Type II procedure is best

used to evaluate a component whichrequires a substantial amount of time for removal and replacement.

This procedure also requires twovehicles, though they do not have to beof the same specification. The vehiclesare identified as “C” and “T.” Vehicle “C”is the control vehicle and as such is notmodified during the course of the test;vehicle “T” is the test vehicle which isused to evaluate the test component.

The minimum mileage for a completetest is 240 miles. This is composed ofthree valid test runs of 40 miles (minimum)each with vehicle “T” running a baselinecomponent (control component) andthen three valid test runs of 40 miles(minimum) each with vehicle “T” runningthe test component. Vehicle “T” starts off first; after approximately 5 minutesvehicle “C” begins its run. The test runstarts and finishes at the same location.

For each test run the amount of fuelused by vehicle “T” is compared to thatused by vehicle “C” in the form of a T/Cratio—the quantity of fuel used by vehicle“T” divided by the quantity of fuel usedby vehicle “C.” To be considered validtest runs, three T/C ratios within a twopercent band must be obtained. This mayrequire one or more additional test runs.Test speed — as required Vehicle loads — not required to

be the sameVehicle warm-up — minimum of one

hour at test speed Test run time — elapsed time of the

test runs must bewithin .5%


79


C. SAE Engineering TypeThe SAE Engineering Type test provides

standardized procedures to evaluate fueleconomy for different modes of operation,such as Long Haul Cycle, Short HaulCycle, Local Cycle, and Transit Cycle.This procedure is more controlled thaneither the Type I or II tests both in termsof test site conditions and test procedures.The effect of this is reflected in greaterrepeatability. This procedure is best runon a test track.

The procedure requires two vehiclespreferably of the same specification. The vehicles are identified as “C” and “T.”Vehicle “C” is the control vehicle and isnot modified during the course of thetest. Vehicle “T” is the test vehicle whichis used to evaluate the test component.

Long Haul Cycle: The minimum mileage for a complete

test is 180 miles. This is composed ofthree valid 30 mile test runs with vehicle“T” running the baseline component(control component) and three valid testruns with “T” running the test component.The start time of the vehicles should be staggered such that they don’t aerodynamically interfere with eachother. Halfway through each test run (15 miles) the vehicles are to come to acomplete stop, idle for one minute andthen accelerate back to the test speed. A test run starts and finishes at the samelocation. If this procedure is not run on a track it can be handled by running 15 miles outbound and 15 miles inbound.

For each test run a T/C ratio isobtained. This is the MPG of vehicle“T” divided by the MPG of vehicle “C.”A test is considered valid if for the threeruns (or more) the spread of T/C ratiosdoesn’t exceed three percent of themean value.Test speed — 55 MPH Vehicle loads — as requiredAmbient temperature — 60 to 80°Wind velocity — average wind speed

not to exceed 15 MPH

Vehicle warm-up — minimum of 1 hour

at 55 MPH

Tire Repairs

S E C T I O N T E N

High loads, speeds and tire operating

pressures place critical importance on tire

maintenance practices. Tire repair is an

integral part of maintaining radial tires to

achieve the maximum in performance and

value. Because of this, personnel should be

adequately trained in repair procedures and

techniques, and only the highest quality

repair materials should be used.

80

Tire Repairs

S E C T I O N T E N

81

Tire Repairs

Tire repairs normally made by fleetoperators and tire service centers are limited to simple punctures such as nailholes. Anything more extensive, such asspot, reinforcement, or section repairsshould be referred to an authorized fullservice Goodyear retreading and repair facility.

Significant cuts and cracks in thesidewall area should be spot repaired as soon as possible to prevent the needfor a major section repair. Frequent tireinspection in service is recommended.

This section gives information concerning tire damage, extent, andlocation, to help determine whether or not section repairs are feasible.

The cutaway view of the Unisteel tirein Figure 10.1 shows the constructiontypical of Goodyear radial truck tires.The single radial ply of steel cord as well as the four steel cord belt plies are evident.

Figure 10.1 Cutaway View of Unisteel Tire

S E C T I O N T E N

82

Tire Repairs

NAIL HOLE REPAIR PROCEDURESRadial tire nail hole repairs up to

3/8-inch diameter (9.5 mm) may be madein the tread face as long as the nail holeis at least one-inch inside the shoulder.All injuries outside this point should betreated as a section repair.

Figure 10.3 Dismount tire. Remove puncturing object.Using a probing awl, determine the size and extent of injury, and angle of penetration. Thoroughlyinspect the inside of the tire for additional damage.Clean area to be repaired inside of tire with scraper and pre-buff cleaner.

Figure 10.5 Apply a coating of chemical cure cementto the leading 1/3 of the cured plug. Remove the end of the plug insertion tool and insert the pluginto the nose piece. Do not contaminate the plug orcross thread the nose piece.

Figure 10.4 Beads in relaxed position. Using a car-bide cutter, drill the injury from the inside to clean andprepare the injury for the plug.

Figure 10.6 Brush chemical cure cement on nozzle andinsert into the hole while turning clockwise.

RADIAL ONLY

Figure 10.2 Any number of repairs in the approved crown area only tread minus outer 1” area(use outer grooves as a guide). Refer larger injuries toa full service repair shop. Do not overlap patches.

Figure 10.7 Apply air pressure (80 psi) to top of gun.This presses the plug through the nozzle into andthrough the injury. Remove the gun while turning in aclockwise direction.

If a pull-through plug is used, insert the plug intothe wire puller, apply chemical vulcanizing cementto the leading 1/3 of the cured plug and pullthrough the injury from the inside of the tire.

Radial Only

Repair Area

S E C T I O N T E N

83

Tire Repairs

RADIAL ONLY

Figure 10.9 If necessary, repeat the liner cleaning procedure with pre-buff cleaner. Using a low-speedgrinder, buff the liner to an RMA1 texture finish.Then vacuum to remove dust and debris.

Figure 10.10 If using a chemical cure repair patch,cement the back of the patch and the buffed liner withchemical vulcanizing cement. If using a “Versacure” typerepair patch, cement the buffed liner only. Thoroughlycover the cemented areas with a light, even coat. Allowproper drying time before applying the repair patch.

*When using chemical cure MCX series patches,use chemical vulcanizing solution on the buffedliner and back of repair patch for heat and non-heat applications.

Figure 10.11 Place beads in a relaxed position. Centerthe patch over the plug and stitch the patch from thecenter out. Directional arrows on the patchmust be properly aligned, after stitching iscomplete. Apply a coat of butyl liner repair sealer tothe patch edges and the over buffed liner. Trim the excessplug no more than 1/8” above the outside tread surface.

Figure 10.8 Cut excess plug 1/16'' above the linersurface on the inside. Do not stretch plug.

Radial Only

S E C T I O N T E N

84

Tire Repairs

RADIAL SECTION REPAIRLIMITS IN SIDEWALLAND SHOULDER AREA

Most sidewall injuries will be thesplit-type, caused by snags and punctures.Maximum injury sizes for sidewall andshoulder repairs are shown below.

The number of these section repairsshould be limited to 2 per tire for linehaul service and 3 for city service with amaximum of 2 repairs per any 90 degreequadrant of the tire as long as repairpatches do not overlap and the same plywires are not affected by more than oneinjury.

Spot repairs may be made withoutlimit providing that the body plies arenot exposed or damaged. Existing repairsmust be reworked if loose or questionable.

NOTEWire must be sound and free of rust.Maximum shoulder and sidewall injury

for typical line haul medium truck tire is 1'' wide (circumferentially) x 4'' long (radially). See authorized Goodyearfull service repair facility for otherappropriate limits.

Figure 10.12

Figure 10.15

Figure 10.16

Figure 10.14

Figure 10.13

Cable 1-1/2

1/8 3-3/4

3/8 5

1/2 5

3/4 5

1 4

MaximumInjury Size

Casing Size (b) (X) Width (Y) Length

10.00R20/2211.00R20/2211R22.5/24.512R22.5285/75R24.5295/75R22.515R22.516.5R22.518R22.5

Max Repair

Body Ply

Maximum Shoulder andSidewall Repair Size

Repair Patch Should Be

Centered Over Injury

Center Patch Over Injury

YX

S E C T I O N T E N

85

Tire Repairs

CROWN REPAIRLIMITS

APPLICATION OFCENTER-OVER-INJURYSECTION REPAIRS RADIAL PLY TIRES

Injuries up to 1-1/2'' diameter may be repaired in line haul and city serviceradials depending on tire size.

Radial mileage tires used in city bus service only may be repaired up to1'' diameter. See authorized Goodyearfull service repair facility for otherappropriate limits.

Figure 10.17

Figure 10.18

Figure 10.20

Figure 10.21

Figure 10.19

Tire Size Dimension A

All “LT” Tires 2-1/2''8.25R, 9.00R, 10.00R 3''9R, 10R, 11R 3''16.5, 18R22.5 3''285, 295, 305,

315/75R, 80R, 85R 3''11.00R, 12.00R 3-1/2''12R, 13R/FR20 3-1/2''12/80R, 13/80R, 14/80R 3-1/2''

Non-Repairable Areas

Sidewall or Shoulder Repair

Center Patch Over Injury

Tread Repair Center Patch Over Injury

Dimension A

Retreading

S E C T I O N E L E V E N

The purpose of this Recommended Practice

is to provide guidelines for the evaluation and

selection of a retread supplier for truck tires.

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Retreading


87

Retreading

Tire retreading is a manufacturingprocess. Therefore, any retreaded tire isonly as good as the workmanship andthe quality control in the plant thatmanufactured it. To thoroughly evaluatea retread supplier, one must look at boththe product and service. For these reasons,a plant visit is important in the selectionof a retreader.

PLANNING A RETREAD PLANT VISIT

Prior to a plant visit, a few itemsshould be considered. These may affectwhether the retreader in question qualifies as a prospective supplier. These considerations include:1. Does the retreader use quality

products and procedures from aquality tread rubber manufacturerproviding assistance to the retreader, ie:a. Production associate trainingb. Q.A. & technical assistancec. Plant certification

2. Does the retreader offer any of thefollowing services you may need?a. Pick-up and delivery of tiresb. Flat repairc. National account programd. Tire mounting and demountinge. 24-hour road service

3. Is the retreader making repairs:a. To both bias and radial casings?b. To all types and levels of tire

injuries: spot repairs, bead repairs, reinforcements, and section repairs?

4. What is the retreader’s turn-aroundtime? Seven day turn-around is typical.

5. Does the retreader define warranty

policy on both retreading and repairs?Is there any casing warranty?

When the retreader has satisfied thatit can meet the needs in these areas, avisit to the plant for an evaluation ofwork methods and quality procedures is invaluable.

A plant inspection is divided intoeight areas of concern. They are in anorder that should be convenient for atour of the plant. Many of the questionsraised will not have absolute or totallyobjective answers. Judgment, and theretreader’s response to questions, willprovide the answers needed to rate anyindividual retread plant.

It is suggested to reproduce the sections listed under “Plant Inspection” in this Recommended Practice for use in discussion with the retreader and itsemployees, and also reproduce the“Retread Plant Inspection Checklist”appearing at the end of this RecommendedPractice to use during a retread plantvisit. The checklist provides space torate each item checked.

Plant Image1. Overall plant appearance should be

clean and orderly.2. The plant must have adequate layout

and space for effective handling of tires.

3. The facility should be well lightedand adequately ventilated.

4. The retread plant must have production capacity to handle your service needs.

5. The retread plant should beinspected and certified by an industry association or supplier.

Casing InspectionThe inspector’s job is to determine

whether the used tire is retreadable as presented. If not, the inspector will usually make recommendations as to thedisposition of the used tire: scrap; repairand then retread; return to the customerfor adjustment consideration; etc. Theability to analyze worn and damagedtires is a skill usually acquired throughexperience and also requires a workingknowledge of all the various steps of theretread process. Look for an experienced person in this position.1. Inspection area must be well lighted.2. Tires must be dry before being

inspected.3. Check to see whether the retreader

is using any electronic, ultrasonic,or other “high-tech” inspectionequipment.

4. Check the retreader’s system oftracking casings in process toensure that all of your casings getback to you and that they arereturned on schedule.

PLANT INSPECTIONINTRODUCTION


88

Retreading

Casing RepairingThe repair person’s job is to make

structural repairs to damaged areas ofthe casing so the casing will be soundenough to last through a new tread life.1. A separate, clean, well lighted area

should be used for the repair area.2. Wall charts should be posted showing

procedures, patch usage, cure times,etc. Retreaders’ recommendationsand procedures must be followed.

3. Repair materials must have currentmanufacture date codes or expirationdate codes. Most repair materialshave a shelf life and, ideally, shouldbe stored in a cool, dry place.

4. All repair materials, cements, andsupplies should be from the samemanufacturer. It is a questionablepractice to mix brands since not all products are compatible.

5. The retreader should identify repairs.(Retread plant name, date of repair, etc.)

6. Check to see that the repair shop is using the proper RPM hand buffing tools.a. A high RPM grinder is used for

grinding steel.b. A low speed grinder is used on

rubber. Use of a higher RPMtool will scorch the rubber,reducing adhesion. (Gummyrubber build-up on buffing raspand smoke generated at thebuffed surface are indicationsof scorching.)

BuffingThe buffing operation is used to size,

shape, and texturize the crown of thecasing in preparation for the applicationof a new tread.

1. All casings must be buffed to a predetermined:

a. Crown widthb. Crown radiusc. Specified remaining undertreadd. Symmetrical profilee. Diameter and bead to bead

dimensions in mold cure systems

2. Buffers should be computer or template controlled. Buffer operatorsshould not override computer programs or templates.

3. Wall charts, or other ready references,should be in use to determine thecorrect specification for each tire as referred to above.

4. All exposed cords (fabric or steel)must be “finished” to remove allfuzz and frayed ends.

5. All exposed cords (fabric or steel)should be coated with cement orother similar treatment promptlyafter completion of the buffingprocess. Steel cords must be coated within 15 minutes.

6. All untexturized areas such as treadgrooves and irregular wear spotsmust be hand-treated to removeoxidation and surface dirt.

7. Buffing rasps should not be smokingexcessively. This would be an indication of scorching and willresult in poor adhesion.

8. Buff texture must be consistent withRubber Manufacturers Associationwww.rma.com guidelines. See theRMA buffed texture chart.

9. Buffed tires must be handled in sucha way as to ensure the buffed surfaceis not contaminated.

After Buff PreparationItems listed in this category include

a number of interim steps between themajor operations of buffing and treadapplication. Depending upon individualretread plant procedures, these stepsmight be performed individually, or aspart of the repairing, buffing, or treadapplication steps.

1. An after-buff inspection should beperformed to ensure the buffingprocess has not uncovered any previously unnoticed defects.

2. All holes, cuts, and penetrations mustbe probed to determine the severityof the injury and to ensure that allforeign material has been removed.

3. Buzz-out/skive-out. Note that this is the single most neglected or mishandled detail and one of themajor causes of retread failures. Alldirt, rust, and foreign material mustbe removed; all separated and/orlaminated rubber must be removed– leaving a clean, solid surface for thefiller material to adhere to. Any buzz-out that exceeds the specified limitsmust be treated as a section repair.

4. Tires must be measured for propermold fit or tread length in the caseof some pre-cure methods.

5. Cement is used to enhance theadhesion between the new treadand the prepared casing.

a. The tire should be clean before cementing.

b. Adequate drying time must beallowed prior to tread application.

c. Cement container must be protected from air supply linemoisture and oil contamination.

d. Check manufacturer’s date codeor expiration date on cementcontainer. Cements have a shelflife and must be kept fresh.

e. The “in use” cement containermust be kept mixed whilebeing used to eliminate thepossibility of solid settling out from the mixture.


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Retreading

Tread ApplicationTread application is the fitting of

new tread rubber (which will becomethe new tread) onto the prepared casing.This rubber must be the correct widthand thickness. It must be centered and itmust be circumferentially consistent.

1. All buzz-outs should be filled flushwith the buffed surface.

2. All exposed cord (fabric or steel)should be covered with cushion gumbefore the tread rubber is applied.

3. Check to see what brand, productline, and grade of tread rubber isbeing used. It is the retreader’sresponsibility to notify his customersif this specification is changed.

4. Raw materials (tread rubber, cushion,etc.) must be fresh. Check the manufacturer’s date code or expirationdate code on the container, and ideally, it should be stored in a cool,dry area.

5. With pre-cure treads there should be no more than two splices pertire. Observe the procedures andmaterials used for making treadsplices for quality.

6. Short tread pieces (18” or less)should not be used to make splices.

7. With pre-cure tread application,“stitching” must be performed insuch a way as to eliminate trappedair pockets.

8. Adhesive surfaces of tread rubberand cushion, and the buffed surfaceof the tire, must be kept free ofcontamination from hands andother sources.

CuringThere are two popular cure systems:

1. Mold Cure. Tread rubber is applied tothe tire uncured. The prepared tireis placed in a mold (matrix) whichimprints the tread pattern as therubber is cured directly on the casing.

2. Pre-Cure. The previously cured treadrubber, with the tread design alreadyformed, is applied to the tire with athin layer of uncured cushion gumon its base to serve as an adhesive.The assembly is then placed in aheated, pressurized chamber wherethe cushion gum is cured to boththe tread rubber and the casing,forming the bond between the two.

3. Time, temperature, and pressure arethe three requirements of any retreadcure system. Increasing or decreasingany of these factors from an optimumlevel will affect such things as treadadhesion, mileage, and casing life.The optimum time/temperaturespecification is determined by completing a thermocouple test in that particular curing equipment.

a. Check to see if the retreaderhas had thermocouple testsmade in his equipment.

b. Ask to see what control systemsor procedures are used to ensurethat all tires are cured at thecorrect temperature, pressure,and time period.

4. All envelopes, diaphragms, and curing tubes must be leak free.

5. Check for steam and air leaks whichmay contribute to improper cure.

6. Tires must be stored in such a manneras to avoid distortion of the treadand/or casing before curing andimmediately after.

7. Wicking material used with pre-curesystems must not be stapled intothe tire sidewall or bead. Sidewallsand beads are not designed to accept

staples. Staples may penetrate thetubeless liner, creating air leaks. Holesfrom staples can allow moisture toenter and create rusting of the steelbody in steel cord tires.

Final Inspection & FinishAfter curing, a final inspection should

be made of the finished retread. At thistime, the finished tire may be trimmedof rubber flashing or overflow, painted,and tagged for delivery.

1. The inspection area must be well lighted.

2. The tire must be inspected on a spreader.

3. It is recommended that tires beinspected immediately after completion of the cure cycle, while still hot. Separations andother flaws that are visible whilehot may disappear as the tire cools.

4. The inside of the tire must beinspected to ensure that all patchesare properly bonded and that nobubbles, dimples, or buckles are evident in the patch or tire liner.

5. The outside of the tire should beinspected for appearance.

6. All staples must be removed fromprecure tread splices and wickingmaterial.

7. Check to see that the DOT identification number has been appliedto the tire. Ideally, the DOT numbershould be located away from thebulge width of the tire so it will notbe scuffed off in service.

8. All rejected returned-as-received (RAR)casings should have the rejectioncause marked on the tire with thearea of injury clearly identified.

9. Finished retreads should be paintedand all crayon marks should bepainted over to give the final productan appealing appearance.


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Retreading

Base Width – A measurement of thatportion of the tread rubber that joins to the buffed surface of the worn tire.

Beads – The anchoring part of the tirethat is shaped to fit the tim. Made ofhigh tensile steel wires wrapped andreinforced by the plies.

Bead Sealing Area – The flat area andheel area of the bead that contacts the rim.With tubeless tires, the bead area sealsto the rim and rim flange to retain air.

Belted Bias Tires – Tires constructed sothe ply cords extend from bead to beadand are laid at alternate angles substantially less than 90˚ to the centerline of the tread. On top of thebody plies are two or more belt pliesextending approximately from shoulderto shoulder running circumferentiallyaround the tire at alternate angles.

Bias Ply Tires – Tires constructed so theply cords extend from bead to bead andare laid at alternate angles substantiallyless than 90˚ to the centerline of the tread.

Body Plies – Layers of rubber-coatedparallel cords extending from bead to bead.

Breaks (Cracks) – A surface openingextending into or through the plies.

Flex Breaks – A break into orthrough one or more plies, usuallyparallel to the beads.

Impact Breaks – A star- or X-shapedor diagonal break into or throughplies, usually visible from the insideof the tire.

Radial Crack – A crack in the outersurface of the tire, usually in thesidewall area proceeding perpendiculartowards the bead.

Tread Cracks (Channel or Groove) –Cracks in the base of the treadgrooves or voids.

Buckled – Any gross distortion of the tire body or tread area evidenced by wrinkling on theinside of the casing.

Buffed Contour – The shape of the buffedtire that usually includes a specifiedradius and width.

Buffed Radius – A measure of the buffedsurface curvature from shoulder to shoulder.

Buffed Texture – That surface producedby buffing, rasping, or cutting as definedby The Rubber Manufacturers Association,“Buffed Textures” (RMA Shop Bulletin No. 29,www.rma.org).

Casing – The complete tire structure.

Cement – An adhesive compound usedto provide building tack. May be brushedor sprayed on the buffed surface.

Check Template – A precut pattern usedto determine the contour of a buffed tireto check compatibility to a matrix.

Cords – The individual strands formingthe plies in a tire.

Cross Section – The section width of atire casing.

Cure – The process of vulcanization of rubber by applying heat and pressurefor a specified time.

Curing Tubes – Special tubes placedwithin the tire while curing.

Diaphragm – A flexible sheet used toencompass part or all of a tire during

retreading in some processes.

Gauge – Thickness, usually expressed in thirty-seconds of an inch, by the decimal system, or in millimeters in themetric system.

Injuries – A break or cut of any shapecaused by a penetrating object or severescuff or impact.

Injury Size – Widest opening in thecord body after skiving and buffing.

Inner Liner – The tubeless tire innersurface used to retain the inflation media.

Kinked (Beads) – A sharp permanent bendin the bead wires at one or more pointsaround the circumference of the bead.

Load Range – Specified as a letter (A, B,C, etc.) to identify a given size tire withits load and inflation limits when used ina specific type of service as defined inTire and Rim Association, Inc. (or equivalent) yearbooks.

Matrix – Aluminum, rubber, or steelrings or segments that form the cavity in which a tire retread is cured and withwhich the tread design is formed.

Nail Hole – A penetration caused by asmall, sharp object, 3/8 inch maximumdiameter.

Outside Steam Bag – A flexible bag,usually reinforced, used to encompassthe tread and tire shoulders of a tirebeing retreaded or repaired.

Plies – Layers of rubber-coated parallel cords.

DEFINITIONS


91

Retreading

Protector Ply – A ply added primarilyfor casing protection which in somecases may be removed during retreading.

Radial Tire – A tire that has ply cordsfrom bead to bead extending at about90˚ to the centerline of the tread. Ontop of the body plies are two or morebelt plies of rubber-coated cords extendingapproximately from shoulder to shoulderand running circumferentially aroundthe tire at alternate angles at substantiallyless than the ply cord angle.

Reinforcement (Repair) – Any material,usually rubber and fabric, vulcanized toa tire to add strength to the tire cordbody at an injury. Repairs to over 25%of plies usually require reinforcement.Repairs of more than 75% of plies areusually called section repairs.

Repair Material – Any rubber compoundor patch material used to make repairs.

Repairing – Reconditioning of portionsof tires injured by punctures, cuts,breaks, cracks, etc. These repairs restorestrength for additional safe service (See Reinforcement, Spot, Sections, Nail Holes).

Retreading (Recapping)

Full Treading – Replacement of theworn tread with rubber extendingover the shoulders.

Top Treading – Replacement of theworn tread area only.

Bead-To-Bead Retreading –Replacement of the worn tread areaand sidewall rubber extending tothe bead.

Precured Tread Retreading –Replacement of the worn treadareas with pre-vulcanized treadscontaining the tread design alreadycured in.

Sections – Reinforced repairs made to acasing where an injury larger than a nailhole extends through more than 75% ofthe plies or through the casing in thetread or sidewall areas.

Separation – Lack of adhesion or cohesionbetween any adjacent materials in a tire.

Tread Separation – Pulling away ofthe tread from the tire body.

Retread Separation – A separationbetween the tread rubber and thebuffed tire casing.

Ply Separation – A separationbetween adjacent layers of cords (plies).

Bead Separation – A breakdown of the bond between components in the bead area.

Belt Edge Separation – A breakdownof the bond between componentsnear the edge of the belt plies.

Shoulder – The upper sidewall areas ofthe tire casing immediately adjacent tothe tread area.

Sidewall – That portion of the tire casingbetween the tread and bead.

Skive – Removal of damaged materialprior to making a repair.

Splices – A junction of the ends of anytire components.

Spot (Repair) – The replacement ofrubber only in an injury that penetratedto no more than 25% of the body pliesin a radial tire. Rubber replacement only.

Stitching – A method used to both removetrapped air and improve rubber contactfor better adhesion.

Synthetic Rubber – Man-made rubber.

Texture – (See Buffed Texture)

Tread – That portion of a tire that comesin contact with the road.

Tread Design – The non-skid pattern ordesign on the tread of a tire.

Tread Grooves – The space betweentwo adjacent tread ribs, lugs, or bars.

Undertread (Replacement) – The rubberbetween the base of the tread grooveand the buffed surface.

Vulcanization – A chemical reactionwhich takes place under appropriatetime, temperature and pressure anddevelops desirable characteristics andproperties. (See Cure)

Weather Checking – Tire sidewall surface crazing or cracking attributableto aging and atmospheric conditionsrather than to flexing.

Wicking – A capillary action caused byfabrics or cords that allows air to escapefrom the tire casing or from under an envelope.


92

Retreading

RETREAD PLANTINSPECTION CHECKLIST

PLANT: ____________________________________________________________ DATE: ____________________________

INSPECTOR(S): __________________________________________________________________________________________

Plant Image

A. Appearance

B. Space and layout

C. Lighting

D. Ventilation

E. Production capacity

F. Outside certification

G. Material storage

H. Evidence of training

Casing Inspection

A. Lighting

B. Dry casings

C. Repairs removed

D. Casing I.D./tracking

Casing Repairing

A. Location and lighting

B. Repair information/procedures

C. Material shelf life dates

D. Material storage

E. Single brand materials

F. Repair I.D.

G. Tool RPMs

Buffing

A. Buffed dimensions, profile

B. Specification information

C. Exposed cords finished

D. Exposed cords cementing

E. Texturize unbuffed areas

F. Mold fit measurement

G. Rasp condition/smoking

H. Buff texture

I. Handling, cleanliness

ACCEPTABLE COMMENTSNOT

ACCEPTABLE


93

Retreading

After-Buff Preparation

A. Holes/cuts probed

B. Buzz-out limits

– Bias

– Radial

C. Cement application

D. Cement dry time

E. Cement shelf life

Tread Application

A. Buzz-outs filled

B. Tread rubber manufacturer

brand/grade

C. Spliced tread rubber

– 2 splices maximum

– minimum 120˚ spacing

D. Handling/cleanliness

Curing

A. Thermocouple tests

B. Controls: pressure,

temperature, and time

C. Air/steam leaks

D. Tire storage–distortion free

E. Staples in tread of tire only

Final Inspection

A. Lighting

B. Inspect on spreader

C. Inspect hot

D. Staples removed

E. DOT serial number

F. RAR identification

ACCEPTABLE COMMENTSNOT

ACCEPTABLE

Miscellaneous

S E C T I O N T W E L V E

The following section explains the use of

chains on radial truck tires. Chain use is

designed to offer additional traction, providing

the chains and tires are matched appropriately

for size and fit. General precautions to tire

siping, dynamometer testing and mixing

radial and bias ply tires are also addressed.

Finally, this section explains the variances

in sound levels produced by radial truck

tires, and the conditions under which

truck noise occurs.

94

Miscellaneous


95

Miscellaneous

USE OF CHAINSON RADIALTRUCK TIRES TIRE SIPING

The use of tire chains can be helpfulin providing additional traction in severeweather conditions (such as ice and heavysnow) especially when traveling in hillyor mountainous terrain. Tire chains can beused safely and successfully with Goodyearradial truck tires provided several simpleand important points are followed.

Always select chains that are specificallydesigned for radial tires. These chainsnormally have shorter cross chains thanolder designs and allow the position ofthe side chains to be higher on the tiresidewall. This is out of the high-flexsidewall area of a radial tire and resultsin less susceptibility to sidewall damage.

Be sure to use the proper chain sizefor the tire on which it is being attached.Tighten chains when they are firstapplied, then after a short run-in period,readjust to ensure a continued snug fiton radial tires. Serious sidewall damagemay result from loose chains.

Check for adequate dual spacing,especially if using single tire chains oneach tire of a dual assembly. The greaterdeflection of the radial tire may requiremore dual spacing in marginally-spaceddual assemblies.

Finally, always remove chains as soonas they are no longer needed.

Tire siping is a process of makingsmall knife-like slits in the tread rubbersurface. Normally this is accomplishedby a machine that uses sharp, highspeedrotating discs to make cuts that are at anangle of 90° to the circumference of thetread. Siping cuts are normally controlledso they are spaced a specific distanceapart from one another. They also willvary in depth across the tread face.

Proponents of tread siping have claimedvarious performance improvements fortruck tires. These claims include improvedtreadwear and reduced irregular wear.

Also, it is often claimed that sipingimproves traction for winter and wetdriving conditions on certain road types.

At present, the majority of truck tiresiping is done in the westernmostMidwest states and the Northwest corridor. It is popular in certain areas,and especially during the winter months,to sipe both steer and drive, and sometimes trailer tires.

Goodyear’s position on siping is thatit may, under certain operating conditions,improve tire performance. However,under the vast majority of truck operatingconditions, new tires are designed andproduced with tread patterns and treadcompounds that do not require treadsiping to give satisfactory performance.

Actual testing indicates that sipingmay improve the tire’s resistance toirregular wear on free-rolling wheelpositions that are susceptible to irregularwear due to the combination of operatingservice and tire application. Specifically,siping may help reduce irregular wearon trailer axles where light, one-wayloads are encountered, such as graintrailers or belly dumps that operateunder extreme load variations fromunloaded to loaded conditions.

On the other hand, siping is generallybelieved to detract from treadwear on lugtype tires used on drive-wheel position.This is because siping tends to break upthe tread pattern and cause increasedbending of the tread elements. Thisresults in faster wear due to increasedscuffing as the tire goes through its footprint under torque.

The effect tread siping has on tireperformance can vary considerably withthe particular tire pattern being siped.For example, in a heavily bladed treadpattern it is believed that siping in theoriginal tread state could hurt treadwear.Other tread patterns, such as those having a much higher net-to-gross footprint area, might be more adaptablefor siping under the service conditionsdiscussed earlier.

If a customer chooses to sipe hisGoodyear tires, we strongly recommendthat he pay close attention to the type ofsiping used. Specifically, our experienceis that siping should be performed laterallyacross the tread, although angles thatvary somewhat from this might also beacceptable. However, to the best of ourknowledge, siping that is more or lesscircumferential has not been demonstratedto be successful. Also, our experienceshows that siping with varying depthacross the face of the tread usuallyyields better results than constant depthsiping. This also appears to provide theminimum risk for increasing the tire’ssusceptibility to tread rubber chunking.

It is important to note that theGoodyear warranty provides protectionfor the user against failures from workmanship or material conditions. If a tire failure occurs because of a condition beyond Goodyear’s control,such as siping, the warranty is null and void.


96

Miscellaneous

DYNAMOMETERTESTS

MIXING RADIALAND BIAS PLY TIRES

In recent years, a number of retreadrubber manufacturers have producedprecure tread rubber that is siped whenmolded. Various claims of improvedtreadwear, fuel economy, etc, have beenmade. Our experience indicates thatwhile these claims may be true in specificinstances, it is largely a matter of sipingthe tread in such a way that is compatiblewith the particular tread rubber compoundand tread pattern design being used. Inother words, if tread siping is consideredan integral part of the manufacture ofnew tread rubber at the outset, the sipingcan be more or less customized to thetype of rubber and type of pattern sothat performance can be optimized.

In summary, tire siping may have certain performance advantages inimproved treadwear and/or traction;however, these can be expected to varyconsiderably, depending on the particulartype of tread rubber, the tread pattern,and the service conditions in which thetire is used. A customer considering siping tires should consult the new tireor retread rubber manufacturer to discussappropriate siping machinery and techniques for the individual situation.

Dynamometers are used by truckmanufacturers, and frequently by truckdistributors or large fleet operators, to testthe engines and other parts of the driveline.

Dynamometer rolls vary in size from8-5/8-inch to 50-inches. The smaller rollshave a greater potential for damagingthe tires.

During a dynamometer check, thereis little weight on the tires and only asmall area of the tread face (usually thecenter rib or center portion of the tread)is in contact with the roll. Excessiveheat builds up in this small area. If thetest runs too long, the excessive heatcan damage the tire to the point whereit could fail later on the highway.

The maximum safe time for runningtires on a dynamometer roll varies withthe roll diameter, speed, the power ortorque transmitted from the tire to theroll, and, to some extent, the load andinflation. Figure 12.1 shows generalrules for limiting the time for maximumpower testing.

For 50 percent power, the time canbe doubled. For 25 percent power, thetime can be quadrupled.

Due to differences in cornering forcecharacteristics and spring rates, the besttire and vehicle performance will beobtained by applying tires of the samesize and construction (radial ply/bias ply)to all vehicle wheel positions. However,different tire constructions are permittedon the steer, drive, and trailer axles oftwo-axle, tandem, and multiple-axlecombinations when the following rulesare observed.

• Never mix different tire sizes or tireconstructions on the same axle.

• If radial tires are mixed with biastires, the best handling will beobtained with the bias tires on the steer axle.

• Bias or radial tires may be used on either axle of two-axle vehicles,providing the vehicle has dual rearwheels or is equipped with SuperSingle wide-base tires.

• Either bias or radial tires may beused on the steering axle of vehicleswith three or more axles. Either allbias or all radial tires should be usedon the nonsteering axles.

• Never mix bias and radial tires in atandem or multiple axle combination.

Always check with the vehicle manufac-turer before changing tire size or con-struction on any vehicle. Carefully evaluate performance changes caused bytire size or construction changes before putting the vehicle back into service.Figure 12.1

50 – 60 MPH – Time Limitat Max Power

Roll Dia

8 5/8'' 3 Min18'' - 20'' 5 Min30'' - 36'' 10 Min48'' - 50'' 15 Min


97

Miscellaneous

NOISETires are one source of noise emitted

by a truck operating at speeds above 35MPH on a highway. In addition to thetires, other major sources of noise are:

• Engine• Radiator fan• Engine exhaust• Engine air intake• Driveline• Aerodynamics (wind noise)

Noise is defined as a disagreeablesound. Pressure waves in the air producesound. The human ear is designed to sensethese pressure waves and transmit signalsto the brain indicating the magnitudeand characteristics of the sound.

The ear mechanism can detect veryfaint sounds with very low air pressureenergy levels and yet can detect andwithstand relatively loud sounds withhigh energy levels without becomingdamaged. To accomplish this wide rangeof hearing, the ear mechanism/brainresponse is not directly proportional tothe sound pressure, but is less sensitiveat the louder end of the range.

The total noise output of a truck isusually measured with an instrumentcalled a sound level meter. The input to the sound level meter is through amicrophone that is placed nominally 50 feet from the center of the highwaylane that is being monitored.

The sound level meter has electroniccircuitry designed to approximate thehuman auditory system. Thus, the inputis varying air pressure caused by thesound — through a microphone — andthe output is a value indicated on a scalethat gives the sound level of the noise.The sound level or more precisely, the sound pressure level, indicates thedegree of loudness to the human ear of a given sound.

Sound level units are measured indecibels, abbreviated dB. Since thehuman ear does not respond the samefor all frequencies of sound, the soundlevel meter has been modified to agreeclosely with the frequency response ofthe human auditory system. When thefrequency adjustments are included, thesuffix (A) is added to the dB unit: dB(A).

The relationship of sound pressure tosound level in the region caused by thetires of a truck is shown in a relativefashion by the curve in Figure 12.2.

Note the relative increase in noise,going from the relatively non-aggressiveradial rib tire to the bias ply rib tire; tothe radial cross rib; to the bias ply crossrib tire.

Also note the nature of the curvewherein greater changes in sound pressureare required to cause a given change insound level at the higher sound pressuresthan at the lower sound pressures.

The data for the curve were obtainedfrom standard SAE J57 tests using a truckwith four test tires on drive axle and tworib tires on steer axle. The test consistedof a 50-mph coast-by with microphoneat 50 feet from the line of travel.

When several sources cause soundwaves to impinge on the ear simultaneously, the ear perceives thesum total of sound air pressure on theear drum; the pressures are additive.However, the sound level perceived bythe overall auditory system is increasedonly according to the logarithmic ruledemonstrated by the curve.

Therefore, when sounds are emitted byvarious sources in a truck, the combinedeffect can be obtained by adding soundpressures and then converting the totalsound pressure to dB(A). If individualsources of sound have already beencomputed or measured in dB(A), thecombinations of these sounds in termsof dB(A) cannot be obtained by additionof the individual dB(A) values.

Sound Level Decibels (A)

RadialRib

Bias PlyRib

Radial Cross

Sound Level = 20 LOG

Note: The reference pressure is usually taken as the sound pressure at the threshold of hearing: thequietest sound that can be heard, 0.0002 microbarof pressure.

Measured Sound PressureReference Sound Pressure

10Bias Ply ProductionCross Rib

400

300

200

10068 70 72 74 76 78 80

Figure 12.2 Relative sound pressure vs. sound level in dB(A) from SAE J57 tests.


98

Miscellaneous

Typical sound levels of various over-the-road truck components and the effect on total sound level of combining these noise sources areshown in Figure 12.3. The tire noisevalue listed assumes the use of eight biasply cross-rib drive tires on the truck.

Typical methods used to reduce trucknoise to meet limits prescribed by laware as follows:

• Reduce speed• Retrofit equipment• Improve maintenance• Remove irregularly worn tires• Restrict lug tires to drive axles• Use radial tires on all axles• Use rib tires on all axles• 87-90 dB(A)

Laws on noise are established by theFederal government, and are administeredby the Environmental Protection Agency(EPA). Active enforcement, however,generally is the responsibility of statehighway authorities.

Since the enactment of the NoiseControl Act of 1972, the EPA has beenempowered to issue regulations controllingthe operational noise levels of interstaterail and common carriers, and the noiseemissions of newly manufactured products.To do this, the EPA must identify a certainarea of commercial endeavor or a certainproduct as a “major noise source.” It thenhas the authority to pursue regulatoryactivity to control and monitor that areaor product. Early on, the railroads, airports,certain manufacturing operations, and ahost of other activities were identified asmajor noise sources in need of regulatoryattention. The Agency specificallylabeled medium and heavy trucks as significant sources of environmentalnoise and has set up standards for thetesting and control of the “total vehiclenoise emission package.” These standards,known as the Interstate Motor CarrierNoise Emission Standards, are containedin Volume 40, Parts 202 and 205, of theCode of Federal Regulations. They havebeen in force since 1975, and apply toall vehicles in over-the-highway serviceas well as to newly manufactured vehicles.They set definite limits for total noiselevels at various speeds and under stationary conditions.

The legislation for in-service interstatemotor carriers requires that overallexternal noise levels for trucks manufactured previous to the 1986model year not exceed the followingvalues, measured at a distance of 50 feetfrom the vehicle centerline:

• 90 dB(A) on highways at speedsgreater than 35 mph

• 86 dB(A) on highways at speeds of 35 mph or less

• 88 dB(A) during stationary runup at governed engine rpm

For trucks of 1986 model year manufacture and later, the standard requires that the external noise level values must not exceed:

• 87 dB(A) on highways at speedsgreater than 35 mph

• 83 dB(A) on highways at speeds of 35 mph or less

• 85 dB(A) during stationary runup at governed engine rpm

New medium and heavy duty trucks(vehicles with GVWR of 10,000 lbs. or greater) must meet noise emissionstandards based on a vehicle accelerationand pass-by test at speeds of up to but not exceeding 35 mph. The noisemeasurement is taken at a distance of 50 feet from the centerline of vehicletravel, and the test is performed by the vehicle manufacturer himself andcertified to the EPA. For medium andheavy duty trucks produced prior toJanuary 1, 1988, manufacturers had totest their vehicles to a maximum externalnoise level of 83 dB(A). For trucks manufactured after January 1, 1988, themaximum external noise level permittedis 80 dB(A).

Figure 12.3 Combining noise sources.

Engine 80

Fan 79

Exhaust 80

Intake 80

Driveline 83

Tires 75-86

82

83

86

87-90 dB(A)

Speeds Above 35 MPH – Six Predominant Noise Sources


99

Miscellaneous

TIRE STORAGERECOMMENDATIONSFor Tires Not Installed on Vehicles1. Oil, Solvents and Grease

Mounted or unmounted tires shouldnever be stored on oily floors or otherwisein contact with solvents, oil or grease.Nor should tires be stored in the same oradjoining rooms with volatile solvents.These solids, liquids or vapors are readilyabsorbed in rubber and will damage andweaken it.

2. OzoneMounted and unmounted tires should

be stored away from electrical devicessuch as motors, generators, arc weldersand switches because they are activesources of ozone. Ozone attacks rubbercausing it to crack perpendicular to anyapplied stress. Such cracking exposes thenew rubber surface at the base of the crackto greater stress and consequently tomore severe ozone attack until eventuallythe cracks can penetrate to the carcasswhere continued rubber degradationcould cause carcass failure. Minor, ozoneinduced, surface cracks will seldom causetire failure, but can form an access routefor foreign material to penetrate the carcass once the tire is placed in service.

3. Heat and LightTires should be stored in a cool place,

away from direct sunlight or strong artificial light. Both heat and light aresources of oxidation of the tire surfaces.The oxidation is characterized by a“crazed” or “alligatored” surface whichdoes not penetrate the rubber deeply.The severity of the oxidation is, of course,a time- and temperature-dependent variable. Long term storage at ambienttemperatures have been equated to shortterm storage at elevated temperatures.For instance, three days storage at 158˚ Fcauses approximately the same loss intensile strength as three years storage at75˚ F. Oxidation may cause sufficientdamage to the inside of an unmountedtire as to cause early tube failure or aslow leak.

4. Undue Stress in StorageIf possible, tires should be stored

vertically on treads. Severely stressedand distorted tires are subject to muchgreater damage from solvent, ozone oroxidative attack than those which arenot stressed or are stressed minimallyand uniformly. Unmounted tires stackedhorizontally (on sidewall) should bepiled symmetrically and never so high as to cause severe distortion to the bottomtire. Tires that are mounted on rims butnot on vehicles should follow the same recommendations as for unmounted tires.

5. Foreign Material - Dirt, WaterUnmounted tires should be stored

under a waterproof covering. Dirt is notharmful to a tire. However, dirt on theinside of a tire placed in service cancause early tube failure or a slow leak.Water on the inside of a tire in servicecan be turned into steam which canquickly destroy the strength of both therubber and the textile members of thetire. Additionally, water and dirt inside a tubeless tire can cause corrosion totubeless rims and plug tubeless values,both a source of potential tire failure.Foreign material on the tire bead seatcould affect air seal and cause air loss.

6. InflationIf tires are mounted on rims and

inflated, pressure should be maintainedat 10 PSI. If tires are inflated and put instorage during warm weather, the initialinflation should be about 15 PSI to offsetthe drop in pressure which will occurduring the cold weather months.

7. Protective CoverIf tires are stacked, first lay a foundation

of clean wood to protect them from dirt,oil, grease, etc. Tires should be coveredwith an opaque or black polyethylenefilm. PVC or any other clear film is notsatisfactory. The polyethylene film willprotect against ozone generated by

electrical sources and cut down on aircirculation which will minimize both the available oxygen and ozone whichdegrade rubber.

8. Do Not Use Paint to Preserve Tires

For Tires Installed on Vehicles1. The storage area surface under each

vehicle should be firm, reasonablylevel, well drained and free of all oil, fuel or grease. Clean 1/4'' - 3/4''gravel under each tire is desirable ifthe area is not paved. Storage shouldnot be permitted on blacktop or oilstabilized surfaces.

2. When storage longer than 6 monthsis anticipated, the vehicle should beblocked up so weight does not reston the tires and inflation pressurereduced to 15 PSI. Storage of suchvehicles should be under cover if possible. Otherwise, tires should be protected from elements by anopaque waterproof covering.

3. If it is not possible to block up thevehicle, inflation pressure in the tiresshould be increased to 25% above theinflation required for the actual loadon the tire in the storage condition.

4. Vehicles should not be moved duringextremely cold weather. Under moderate temperature conditions,vehicles may be moved if necessary.

5. Inflation in the tires must be adjustedto the recommended service pressurebefore shipping or putting a storedvehicle into service.

6. Both tires and vehicles should be usedon a first-in, first-out basis to avoidexcessive aging due to storage.

7. Based on varying weather conditions,if tires are stored uncovered on vehicles under load, some weatheringmay occur at approximately one yearstorage period.

TIRE STORAGERECOMMENDATIONS


100

Miscellaneous

A tire has delivered its full originaltread life and this warranty ends whenthe tread wear indicators become visible, or five (5) years from he date oforiginal tire manufacture or original newtire purchase date (whichever comes first).

How Do I Know When MyTires Were Maufactured?

Tires with a Department ofTransportation (DOT) number endingwith 0100 or later were manufacturedafter 1/1/2000.

0100 is the 4-digit production date inweek-week-year-year format. 0100means the tire was produced in the 1stweek of 2000. Prior to January 2000, a3-digit date code was used following aweek-week-year format. thus, 019 meansthe tire was produced in the 1st week of 1999.

There are many vendors that sellaftermarket tire sealants and balancematerials that can be added or pumpedinto a tire. Goodyear does not endorseany product, but if you wish to use sucha product as either a sealant or tire balancer, the Goodyear warranty isvoided if the material adversely affectsthe tire inner liner.

WHEN DOES THEWARRANTY END

TIRE SEALANTS ANDBALANCE MATERIALS

Standards &

Regulations

Both truck tire manufacturers and truck tire

users are covered by a number of federal and

state regulations designed to assure the safety

of the motoring public. Some of the more

important requirements of these regulations

are discussed in the following section, including

Federal Motor Carrier Safety Regulations,

Commercial Vehicle Safety Alliance and

Regrooving/Tire Siping Regulations.

S E C T I O N T H I R T E E N

101

Standards &Regulations


102


FEDERAL MOTOR VEHICLE SAFETYSTANDARDS TESTING AND CERTIFICATION

The federal regulations which pertainto the performance and safety of trucktires fall generally into two categories.Those regulations which affect the testing,certification, and marking of newly manufactured tires are contained in Volume49 of the Code of Federal Regulations(CFR), Part 571, and are referred to as“Federal Motor Vehicle Safety Standards.”Those which cover over-the-highwayusage and application are contained inVolume 49 of the same Code, but in Parts350 through 399, and are called “FederalMotor Carrier Safety Regulations.”

The differentiation between newlymanufactured items and over-the-highwayusage is quite clear. Thus, a tire manufacturer is concerned with complyingwith the Motor Vehicle Safety Standardsregarding testing, certification and markings, while the owner or operator of a vehicle who is using the tires inservice must be in compliance with theMotor Carrier Safety Standards in regardto the application, usage and conditionof those tires.

Standard 119 makes demands beyondsimply testing. For one thing, the tire mustcarry a serial code of up to eleven digits orcharacters on one sidewall indicating thename of the manufacturer, the producingplant, the tire size, the tire type (brandname, load range, sidewall description,etc.), and the week and year of production.This information becomes especiallyimportant for record keeping and recallwork. For another, the tire must carryinformation clearly molded into the sidewall to give the consumer a varietyof facts about the product, such as size,type, load range, generic names of materials,construction type, whether for single ordual usage, maximum load and inflationdata, and of course the DOT symbol andserial code. The manufacturer must alsoinclude treadwear indicators evenlyspaced around the circumference of thetire to indicate visually when the tire hasworn to a tread depth of 2/32''.

The regulations encompassed by theFederal Motor Vehicle Safety Standardsfor newly manufactured products areadministered by the National HighwayTraffic Safety Administration (NHTSA),a branch of the U. S. Department ofTransportation (DOT). Those laws contained within the Federal MotorCarrier Safety Regulations are administeredby the Federal Highway Administration(FHWA), also a branch of the DOT, andenforced by the Bureau of Motor CarrierSafety (BMCS), a sub-agency of the FHWAand one of the few true enforcementarms within the DOT.

Part 571.119 of Volume 49 of theCode of Federal Regulations, known asFederal Motor Vehicle Safety Standard119 (FMVSS 119), requires that a varietyof tests be performed by a tire manufacturerto certify that a specific size of a tire linemeets Federal safety requirements. Themain purpose of this law is to ensure tire testing and certification to specificperformance parameters in the areas ofendurance and strength. By randomlysampling and laboratory testing tires inthis manner during production periods, a tire manufacturer certifies that hisproduct meets the minimum safetyrequirements established by law. He alsoproperly qualifies his tires to carry the“DOT” stamping on the sidewall. Sincethis DOT marking must appear on anytire legally sold for over-the- highwayuse in the U.S., it becomes essential for amanufacturer to test and certify his tiresto Motor Vehicle Safety Standard 119.

The other Federal Motor VehicleSafety Standard which effects truck tiresis FMVSS 120, which spells out tire andrim selection and matching requirementsfor vehicle manufacturers. This standardis intended to ensure that when a consumerpurchases a new vehicle, the total maximumload capacities on any axle are at least asgreat as the gross weight rating of thataxle, so that the load carrying capacityof the tires is not exceeded so long asthe vehicle is properly loaded.

SUBPART G — MISCELLANEOUSPARTS AND ACCESSORIES

§393.75 Tires.(a) No motor vehicle shall be operat-

ed on any tire that (1) has body ply orbelt material exposed through the treador sidewall, (2) has any tread or sidewallseparation, (3) is flat or has an audibleleak, or (4) has a cut to the extent thatthe ply or belt material is exposed.

(b) Any tire on the front wheels of abus, truck, or truck tractor shall have atread groove pattern depth of at least4/32 of an inch when measured at anypoint on a major tread groove. Themeasurements shall not be made wheretie bars, humps, or fillets are located.

(c) Except as provided in paragraph(b) of this section, tires shall have atread groove pattern depth of at least2/32 of an inch when measured in amajor tread groove. The measurementshall not be made where tie bars, humpsor fillets are located.

(d) No bus shall be operated withregrooved, recapped or retreaded tireson the front wheels.

(e) No truck or truck tractor shall beoperated with regrooved tires on the

Federal Motor Carrier

SAFETYREGULATIONSTITLE 49 CODE OF FEDERAL REGULATIONS

PARTS 40, 325, 383, 385, 386, 387, 390–397, 399

U.S. DEPARTMENT OF TRANSPORTATIONFEDERAL HIGHWAY ADMINISTRATION

SEPTEMBER, 1993

American Trucking Associations


103


INSPECTIONfront wheels which have a load carryingcapacity equal to or greater than that of8.25-20 8 ply-rating tires.

(f) Tire loading restrictions (except onmanufactured homes). No motor vehicle(except manufactured homes, which aregoverned by paragraph (g) of this sec-tion) shall be operated with tires thatcarry a weight greater than that markedon the sidewall of the tire or, in theabsence of such a marking, a weightgreater than that specified for the tires inany of the publications of any of theorganizations listed in Federal MotorVehicle Safety Standard No. 119 (49CFR 571.119, S5.1(b)) unless:

(1) The vehicle is being operatedunder the terms of a special permitissued by the State; and

(2) The vehicle is being operated at areduced speed to compensate for the tireloading in excess of the manufacturer'srated capacity for the tire. In no case shallthe speed exceed 80 km/hr (50 mph).

(g)(1) Tire loading restrictions formanufactured homes built before January 1, 2002. Manufactured homesthat are labeled pursuant to 24 CFR3282.362(c)(2)(i) before January 1, 2002,must not be transported on tires that areloaded more than 18 percent over theload rating marked on the sidewall of thetire or, in the absence of such a marking,more than 18 percent over the load ratingspecified in any of the publications ofany of the organizations listed in FMVSSNo. 119 (49 CFR 571.119, S5.1(b)).Manufactured homes labeled beforeJanuary 1, 2002, transported on tiresoverloaded by 9 percent or more mustnot be operated at speeds exceeding 80km/hr (50 mph).

(2) Tire loading restrictions for manu-factured homes built on or after January1, 2002. Manufactured homes that arelabeled pursuant to 24 CFR 3282.362(c)(2)(i) on or after January 1, 2002,must not be transported on tires loadedbeyond the load rating marked on the

sidewall of the tire or, in the absence ofsuch a marking, the load rating specifiedin any of the publications of any of theorganizations listed in FMVSS No. 119(49 CFR 571.119, S5.1(b)).

(h) Tire inflation pressure. (1) Nomotor vehicle shall be operated on a tirewhich has a cold inflation pressure lessthan that specified for the load beingcarried.

(2) If the inflation pressure of the tirehas been increased by heat because ofthe recent operation of the vehicle, thecold inflation pressure shall be estimatedby subtracting the inflation buildupfactor shown in Table 1 from themeasured inflation pressure.

A regular program of tire inspection isessential for the prevention of rapid airloss failures. At a minimum, tires shouldbe inspected at the time of the regularpreventive maintenance checks.

The Bureau of Motor Carrier Safetyrecommends an inspection by the driverprior to every trip in its “Truck Driver’sPre-trip Check List.”

In any tire inspection routine, tiresshould be inspected for the followingconditions. If any are found, the tireshould be removed and repaired, retreadedor scrapped as the condition indicates.

• Any blister, bump or raised portionanywhere on the surface of the tiretread or sidewall (other than a bumpmade by a repair). These indicatethe start of internal separation.

• Any cut that reaches to the belt orply cords, or any cut that is largeenough to grow in size and depth.

• Any nail or puncturing object.• If any stone or object is held by a

tread groove and is starting to drillinto the tread base, remove the object.

• Look for skid spots and irregular wearconditions and refer to the chapter onalignment, irregular wear, and rotation.

The owner or operator should also beaware that the use of recapped, retreaded,or regrooved tires is restricted by theBMCS, Federal Motor Carrier SafetyRegulations, and some state regulations,and that the Rubber ManufacturersAssociation recommends against theiruse in certain applications.

In addition to the routine type ofcommon-sense, owner-performed tireinspection just described, there aremandatory inspections which involveagents and agencies of the federal government. For example, the inspectionof tires for defects is required by NHTSAVehicle In Use Inspection Standards, and by BMCS, Federal Motor CarrierSafety Regulations.

Part 396 of the Federal Motor CarrierSafety Regulations authorizes specialagent personnel of the Federal Highway

Table I — Inflation pressure measurement correctionfor heat

Minimum inflation pressure buildup

Average speed Tires with Tires with overof tire in 4,000 lbs. 4,000 lb.previous hour (1,814 kg) (1,814 kg)

maximum load load ratingrating or less

41 to 55 mph 5 psi 15 psi(66 to 88.5 (34.5 kPa) (103.4 kPa)km/hr)


104


Administration, including Bureau ofMotor Safety inspectors, to performinspections of a motor carrier’s vehicleswhich are currently in operation. Theseinspections may be performed at a facili-ty of the motor carrier (such as a termi-nal) or at some other location (such ason-highway) at the discretion of theinspector. The results of these inspec-tions are recorded in a Driver-EquipmentCompliance Check report. If the checkis done at a location other than one ofthe motor carrier’s facilities, the driver isrequired to deliver this report to themotor carrier upon his arrival at the car-rier’s next terminal, or to mail it to thecarrier if he is not scheduled to be in aterminal within 24 hours after the time ofthe inspection. The motor carrier thenhas 15 days from the inspection date tocorrect any violations or defects, certifyany action taken using Form MCS-63,and return the form to the BMCS officeaddress indicated on the report.

Part 397 of the same regulationrequires that for the transport of haz-ardous materials, vehicles equipped withduals on any axle must have the tiresinspected every two hours or 100 miles,whichever occurs first, for the durationof the trip.

Minimum tread groove depths arespecified for tire manufacturers underFederal Motor Vehicle Safety Standard119, and for in-use applications byFederal Motor Carrier Safety Regulations,part 393.75. Under FMVSS 119, manufacturers must include tread depthindicators, commonly called “wear bars”,in six locations evenly spaced aroundthe circumference of a highway trucktire, so that they become visible when2/32'' of tread groove depth is remaining.

Under FMCSR Part 393.75, operatorsare required to maintain at least 4/32'' oftread groove depth on the front tires ofany bus, truck, or truck tractor coveredby that law, and the standard 2/32''remaining tread depth on the otherwheel positions.

In conjunction with the federallyrequired tire inspections previouslymentioned, much work has been doneto promote commonly performed andrecognized tire inspection criteria withinthe scope of the total vehicle inspectionprogram in use by the CommercialVehicle Safety Alliance (CVSA).

The CVSA is a voluntary organizationmade up of states and provinces whichhave responsibility for commercial vehiclesafety operations and which performvehicle inspections and conduct othersafety related programs. The aims of the organization are to maximize theutilization of commercial vehicle, driverand cargo inspection resources, to avoidduplication of effort, to expand thenumber of inspections performed on aregional basis, to advance uniformity ofinspection, and to minimize delays inindustry schedules which could resultfrom this type of enforcement activity.

The CVSA does not supersede or countermand any legally requiredinspection process or any state laws. It is simply a working agreement amongmember jurisdictions to use standardizedprocedures. It has gained widespreadacceptance and has made great progress toward providing a commoninspection program.

CVSA members inspect vehicles on-highway and in terminals. Areas covered by a CVSA vehicle inspectionare the driver (license, hours-of-servicerecords, medical certificate), steeringmechanism, brakes, brake lights/turn signals, drawbars, suspension, fifth wheels,air loss and warning, wheels and tires.Vehicles which pass the inspection areissued a CVSA decal, colored differentlyfor each quarter of the year, and honoredfor the month of issuance plus the

MINIMUMTREAD DEPTHS

COMMERCIAL VEHICLESAFETY ALLIANCE(CVSA)


105


following two months by all participatingstates and provinces.

Criteria for the tire inspection portionof the CVSA inspection program recommends replacement of a tire with any of the following conditions:

Steering Axle of Power Unit• Less than 2/32-inch tread depth at

two, adjacent, major tread groovesanywhere on the tire.

• Portion of breaker strip or casing plyvisibe in tread.

• Sidewall is cut, worn, or damagedthereby exposing ply cord.

• Labeled “Not for Highway Use” or other marking excluding currentapplication (Excluding farm/off-road vehicles briefly on the road.

• Bulge suggesting tread/sidewall separation. Exception: Bulge from sectionrepair (sometimes identified by adjacent blue,triangular label) is not a defect unless higherthan 3/8 inch.

• Tire flat or has leak that’s felt or heard.

• Mounted/inflated so tire contacts partof vehicle.

• Tire overloaded, including overloadresulting from under-inflation.Exception: Does not apply to special permit vehicle operated at a speed low enoughto compensate for underinflation.

Drive/Trail Tires Out of Service• 75 percent or more tread width loose

or missing, in excess of 12 inches oftire’s circumference.

• Less than 1/32 inch tread depth at twoadjacent, major tread grooves at threeseparate locations on tire. With duals,both tires must have listed defect towarrant out-of-service judgement.

• Tire flat or has leak that can be felt or heard.

• Bias-ply tire with more than one plyexposed in tread area or sidewall, orwhen exposed area of top ply exceeds2 square inches. With duals, both tiresmust have listed defect to warrant out-of-service judfgement.

• Radial tire with two or more pliesexposed in tread area, or damagedcords evident in sidewall or exposedarea on sidewall exceeding 2 squareinches. With dual, both tires musthave listed defect to warrant out-of-service judgement

• Bulge suggesting tread/sidewall separation. Exception: Bulge from sectionrepair (sometimes identified by adjacent blue,triangular label) is not a defect unless higherthan 3/8 inch.

• Mounted or inflated so tire contactspart of vehicle or in the case of a dualassembly, its mate.

• Tire overloaded, including overloadresulting from under-inflation.Exception: Does not apply to special permitvehicle operated at a speed low enough to compensate for underinflation.

Regrooving is used in certain types ofservice to extend the mileage obtainablefrom the original tire tread. Tires designedwith sufficient undertread depth to permitregrooving are labeled on the sidewallsas regroovable. Undertread depth refersto the thickness of tread compoundbetween the bottom of the original treadgrooves and the top of the uppermostbreaker or belt. The use of regrooving ismore common in intra-state bus servicethan in trucking fleets.

Goodyear recommends retreadingradial tires for truck use rather thanregrooving. If retreading is not practical,front tires can be regrooved and movedto trailers. Drive tires should be takenoff when about 80 percent worn, thenon-skid depth increased by regrooving,and then reapplied to the drive axle.

Regrooving requires probing the depthof the undertread so that a minimumundertread depth of 3/32 inch remainbelow the newly cut groove. It is recommended that the local Goodyearrepresentative be contacted for informationif regrooving is being considered.

Tire Siping For TractionAdding tire siping to new or partially

worn rib tires for additional traction (as differentiated from regrooving worntread for additional mileage) is anaccepted practice for trucking fleetsoperating on and off the road.

Partially worn radial lug tires can also benefit from regrooving the treadpattern down to 80% of the deepestportion of the original non-skid depthfor added traction.

REGROOVING/TIRE SIPING

106

S E C T I O N T H I R T E E NStandards &Regulations

DOT Regulations On Regrooved TirePurpose and Scope

This part sets forth the conditionsunder which regrooved and regroovabletires manufactured or regrooved afterthe effective date of the regulation maybe sold, offered for sale, introduced forsale or delivered for introduction intointerstate commerce.

Definitions(A) Regroovable tire means a tire,

either original tread or retread, designedand constructed with sufficient treadmaterial to permit renewal of the treadpattern or the generaton of a new treadpatternin a manner which conforms tothis part.

(B) Regrooved tire means a tire, eitheroriginal tread or retread, on which thetread pattern has been renewed or a newtread has been produced by cutting intothe tread of a worn tire to a depth equalto or deeper than the molded originalgroove depth.

Applicability(A) General. Except as provided in

paragraph (B) of this section, this partapplies to all motor vehicle regrooved or regroovable tires manufactured orregrooved after the effective date of the regulation.

(B) Export. This part does not applyto regrooved or regroovable tires intendedsolely for export and so labeled or tagged.

Requirements(A) Regrooved tires. (1) Except as per-

mitted by paragraph (A)(2) of this sec-tion, no person shall sell, offer for sale,or introduce or deliver for introductioninto interstate commerce regrooved tiresproduced by removing rubber from thesurface of a worn tire tread to generate anew tread pattern. Any person who

regrooves tires and leases them to own-ers or operators of motor vehicles andany person who regrooves his own tiresfor use on motor vehicles is consideredto be a person delivering for introduc-tion into interstate commerce within themeaning of this part.

(2) A regrooved tire may be sold,offered for sale, or introduced for sale ordelivered for introduction into interstatecommerce only if it conforms to each ofthe following requirements:

(a) The tire being regrooved shall be a regroovable tire;

(b) After regrooving, cord materialbelow the grooves shall have a protective covering of tread material at least 3/32 inch thick;

(c) After regrooving, the new groovesgenerated into the tread materialand any residual original moldedtread groove which is at or belowthe new regrooved depth shallhave a minimum of 90 linearinches of tread edges per linearfoot of the circumference;

(d) After regrooving, the new groovewidth generated into the treadmaterial shall be a minimum of3/16 inch and a maximum of 5/16 inch;

(e) After regrooving, all new groovescut into the tread shall provideunobstructed fluid escape passages; and

(f) After regrooving, the tire shall not contain any of the followingdefects, as determined by a visualexamination of the tire eithermounted on the rim, or dismounted,whichever is applicable:(i) Cracking which extends to

the fabric.(ii) Groove cracks or wear

extending to the fabric, or(iii) Evidence of ply, tread or

sidewall separation.

(g) If the tire is siped by cutting thetread surface without removingrubber, the tire cord material shallnot be damaged as a result of thesiping process, and no sipe shallbe deeper than the original orretread groove depth.

(B) Siped regroovable tires. No personshall sell, offer for sale, or introduce forsale or deliver for introduction intointerstate commerce a regroovable tirethat has been siped by cutting the treadsurface without removing rubber if thetire cord material is damaged as a resultof the siping process, or if the tire issiped deeper than the original or retreadgroove depth.

Labeling ofRegroovable Tires

Each tire designed and constructedfor regrooving shall be labeled on bothsidewalls with the word “Regroovable”molded on or into the tire in raised orrecessed letters 0.025 to 0.040 inch. Theword “Regroovable” shall be in letters0.38 to 0.50 inch in height and not lessthan 4 inches and not more than 6 inchesin length. The lettering shall be locatedin the sidewall of the tire between themaximum section width and the bead inan area which will not be obstructed bythe rim flange.

See Page 102 (Subpart G -Miscellaneous Parts and Accessories) for the Federal Motor Carriers Safety Regulatons regarding regrooved tires.

107

LOAD RATINGS AND INFLATION DATA FOR RADIAL TRUCK TIRESTubeless Tube Type Load Range Load Range Load Range Load Range Load Range Load Range Load Range

Dual Tire Load Rating D E F G H J L7.50R16LT 2140@65 2440@80LT225/75R16 2150@65 2470@80LT245/75R16 2381@65 2778@80LT215/85R16 2150@65 2470@80LT235/85R16 2381@65 2778@80 [email protected] 2070@65 [email protected] 2445@65 [email protected] [email protected] [email protected] 8.25R15 3660@105 3970@110 5675@125*10R17.5 [email protected] 10.00R15TR 4430@95 4850@110 [email protected] 2700@80 [email protected] 8.25R20 [email protected] 9.00R20 4875@100 [email protected] 10.00R20 5750@105 [email protected] 11.00R20 5780@95 [email protected] 7160@125

12.00R20 [email protected] 9610@105*

11R24.5 10.00R22 6000@105 [email protected] 11.00R22 6720@110

11.00R24 [email protected] 8100@110

215/75R17.5 4540@125*225/70R19.5 3415@95245/70R19.5 3875@85 4375@100265/70R19.5 4750@105255/70R22.5 5070@115245/75R22.5 4410@110265/75R22.5 4805@100295/75R22.5 5675@100 6005@110295/80R22.5 6610@115315/80R22.5 7610@120 7750@120*

13/80R20 7160@110285/75R24.5 5675@100

Single Tire Load Rating7.50R16LT 2440@65 2780@80LT225/75R16 2335@65 2680@80LT245/75R16 2623@65 3042@80LT215/85R16 2335@65 2680@80LT235/85R16 2623@65 3042@80 [email protected] 2350@65 [email protected] 2780@65 [email protected] [email protected] [email protected] 8.25R15 4070@105 4410@110 6005@125*10R17.5 [email protected] 10.00R15TR 5050@105 5530@120 [email protected] 2800@80 [email protected] 8.25R20 [email protected] 9.00R20 5150@100 [email protected] 10.00R20 6175@105 [email protected] 11.00R20 6590@105 [email protected] 8270@125

12.00R20 [email protected] 10960@115*

11R24.5 10.00R22 6430@105 [email protected] 11.00R22 7660@120

11.00R24 [email protected] 9230@120

215/75R17.5 4805@125*225/70R19.5 3640@95245/70R19.5 4080@85 4545@100265/70R19.5 5000@105255/70R22.5 5510@115245/75R22.5 4675@110265/75R22.5 5205@110295/75R22.5 6175@110 6610@120295/80R22.5 7390@115315/80R22.5 8270@120 9000@120*

13/80R20 8050@11014/80R20 9090@120365/80R20 10000@130

285/75R24.5 6175@110385/65R22.5 9370@120425/65R22.5 10500@110445/65R22.5 12300@120Notes: 1. With above loads and inflations, the maximum speed is 65 MPH.

2. For ML tires, see Tire and Rim Year Book for separate ML table.*55 MPH max.

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CLASS ONE6,000 lbs. or less

Full Size Pickup Mini Pickup Minivan SUV Utility Van

CLASS TWO6,001 to 10,000 lbs.

Crew Size Pickup Full Size Pickup Mini Bus Minivan Step Van

CLASS THREE10,001 to 14,000 lbs.

City Delivery Mini Bus Walk In

CLASS FOUR14,001 to 16,000 lbs.

City Delivery Conventional Van Landscape Utility Large Walk In

CLASS FIVE16,001 to 19,500 lbs.

Bucket City Delivery Large Walk In

CLASS SIX19,501 to 26,000 lbs.

Beverage Rack School Bus Single Axle Van Stake Body

CLASS SEVEN26,001 to 33,000 lbs.

City Transit Bus Furniture

Refuse Tow

High Profile Semi Home Fuel Medium Semi Tractor

CLASS EIGHT33,001 lbs. & over

Cement Mixer Dump

Semi Sleeper Tour Bus

Fire Truck Fuel Heavy Semi Tractor

TRAILERS

Auto Transport Double Van Drop Frame Dry Bulk Dump Trailer Flatbed

Flatbed Low Boy Logger Reefer Tanker Van Trailer

Refrigerated Van

Utility Van

TRUCK TYPE AND WEIGHT CLASSThe vehicle icons on the following page depict examples of vehicles in each DOT classification 1-8 with corresponding load

ranges. These classifications are guidelines in understanding the type of vehicle used for different applications by vehicle class.

109

Ackerman Steering Effecton Tire Wear........................................47

Alignment................................................43Ackerman Steering Effect on

Tire Wear ...........................................47Camber...................................................46Caster.....................................................46Drive Axle Alignment ...............................48In-Service Alignment

Recommendations .................................49Loaded vs. Unloaded Alignment

Settings ...............................................45Steer Axle Alignment ................................45Toe.........................................................46Trailer Axle Alignment..............................49

Bearing Adjustment.................................55Branding Tires .........................................35

Camber....................................................46Caster.......................................................46Center-Over-Injury Section Repairs ......85Chains on Radial Truck Tires .................95Collecting and Storing

Tire Information ..................................35Branding Tires .........................................35Radio Frequency

Identification Tags ................................36Radio Frequency Tag Usage......................36

Commercial Vehicle Safety Alliance(CVSA)..............................................104

Cross-Sectional View of Typical Tire.......6Crown Repair Limits...............................85

Demounting ............................................24Drive Axle Alignment.............................48Drive Tires...............................................54Dynamometer Tests................................96

Factors Affecting Treadwear...................50Bearing Adjustment...................................55Drive Tires ..............................................54Environmental Effects ................................56How Speed Affects Tire Wear.....................57Setback Steer Axles...................................53Steer Tire Wear ........................................52

Factors Affecting Truck Fuel Economy..63Appendix ................................................78Environmental Conditions..........................74Summary................................................77Tire Description and Specifications..............76Tire Selection and Maintenance ..................70Vehicle and Engine Design.........................64Vehicle Operation ....................................67

Federal Motor CarrierSafety Regulations.............................102

Federal Motor Vehicle Safety StandardsTesting and Certification..................102

In-Service Alignment Recommendations..49Inflation ...................................................37

Do’s and Don’ts for MaintainingProper Inflation Pressure........................42

Nitrogen Inflation ....................................42Underinflation .........................................40

Inspection..............................................103Inspection Procedures.............................31Installation...............................................23

Loaded vs. UnloadedAlignment Settings..............................45

Lubrication ..............................................20

Matching of Duals ..................................25Minimum Tread Depths .......................104Mixing Radial and Bias Ply Tires............96Mounting and Inflation ..........................29Mounting Procedure...............................19

Assembly of Tire Tube Flap........................22Demounting.............................................24Inspection Procedures ................................31Installation..............................................23Lubrication..............................................20Matching of Duals...................................25Mounting and Inflation ............................29Operation ...............................................31Proper Matching of Rim Parts...................27Safety Instructions....................................20Safety Precautions....................................28Servicing Tire and Rim .............................31Spacers ...................................................26Spacing of Duals .....................................26Tire and Rim Cleaning..............................21Tubeless Tire Mounting .............................23Tubes and Flaps .......................................22Wheel Inspection Guidelines .......................20

Nail Hole Repair Procedures..................82Nitrogen Inflation ...................................42Noise........................................................97

Operation ................................................31

Planning A Retread Plant Visit...............87Plant Inspection ......................................87Proper Matching of Rim Parts................27

Radial Ply Tires........................................85Radial Tire Section Repairs.....................84Radial Tires ..............................................84Radial Section Repair Limits ..................84Radial Truck Tire Terms............................5

Cross-Sectional View of Typical Tire ............6Radio Frequency Identification Tags......36Radio Frequency Tag Usage...................36Regrooving/Tire Siping.........................105

Tire Siping for Traction...........................105DOT Regulations on Regrooved Tire .......106Labeling of Regroovable Tires...................106

Retread Plant Inspection Checklist........92

Retreading ...............................................86Definitions ..............................................90Introduction.............................................87Planning A Retread Plant Visit .................87Plant Inspection .......................................87Retread Plant Inspection Checklist ..............92

Safety Instructions...................................20Safety Precautions...................................28Section Repair Limits in

Sidewall and Shoulder Area................84Servicing Tire and Rim ...........................31Setback Steer Axles.................................53Siping.......................................................95Spacers.....................................................26Spacing of Duals .....................................26Speed and Tire Wear ..............................57Standards and Regulations ...................101

Commercial Vehicle Safety Alliance(CVSA) ...........................................104

Federal Motor CarrierSafety Regulations .............................102

Federal Motor Vehicle Safety StandardsTesting and Certification......................102

Inspection..............................................103Minimum Tread Depths ..........................104

Steer Axle Alignment..............................45Steer Tire Wear .......................................52

Tire and Rim Cleaning............................21Tire Description & Specifications...........76Tire Industry Definitions ........................90Tire Repairs..............................................80

Application of Center-Over-InjurySection Repairs ....................................85

Crown Repair Limits ................................85Nail Hole Repair Procedures......................82Radial Ply Tires ......................................85Radial Tire Section Repairs .......................84Radial Tires ............................................84Radial Section Repair Limits......................84Section Repair Limits in

Sidewall and Shoulder Area ...................84Tire Sealants And Balance Materials ....100Tire Selection & Maintenance ................70Tire Selection Process ...............................9Tire Selection Process Work Sheet ........16Tire Siping/Regrooving.........................105

Tire Siping for Traction...........................105DOT Regulations on Regrooved Tire .......106Labeling of Regroovable Tires...................106

Toe ..........................................................46Trailer Axle Alignment............................49Tube Flap Assembly ................................22Tubeless Tire Mounting ..........................23Tubes and Flaps .......................................22

Underinflation.........................................40

Vehicle and Engine Design ....................64Vehicle Operation...................................67

Wheel Inspection Guidelines.................20

INDEX

Radial Truck Tire And Retread Service Manual · PDF fileForward This manual was prepared as a...

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