Chapter 27 Bennet
Transcript of Chapter 27 Bennet
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Objectives (1 of 2)
Identify the wheel configurations used on heavy-duty trucks.
Explain the difference between standard and wide-base wheel systems and stud- and hub-piloted
mountings. Identify the common types of tire-to-rim hardware
and describe their functions.
Explain the importance of proper matching andassembly of tire and rim hardware.
Outline the safety procedure for handling andservicing wheels and tires.
Describe brake drum mounting configurations.
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Objectives (2 of 2)
Perform wheel runout checks and adjustments.
Properly match tires in dual and tandem mountings.
List the major components of both grease- and oil-lubricated wheel hubs.
Perform bearing and seal service on grease-lubricated front and rear wheel hubs.
Perform bearing and seal service on oil-lubricatedfront and rear wheel hubs.
Perform front and rear bearing adjustment. Describe TMC wheel-end procedure.
Outline the procedure for installing pre-set bearingwheels.
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Cast Spoke Wheels
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Spoke Wheel Duals
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Disc Wheels
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Hub-Piloted Wheel
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Stud-Piloted Wheel
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Wide-base Wheels
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Tires
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Construction of
Bias Ply and Radial Tires
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Tire Size
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Shop Talk
Learn how to identify stud- and hub-piloted
disc wheels: Improper torquing procedure
and sequencing of stud-piloted wheels is a
major cause of wheel failure. With the cone locknut design, a flat washer is
seated directly against the wheel face. The
nonrotating washer prevents galling of thewheel surface.
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Shop Talk
Revolutions per mile data on the drive axle tiresmust be correctly programmed to the chassis databus.
Whenever tires are replaced or swapped on a
vehicle, ensure that you check and reprogram tirerevolutions per mile to the appropriate controller onthe chassis data bus.
This data is used to calculate and broadcast road
speed data to the instrument cluster, engine,transmission, collision warning, and othercontrollers networked to the data bus.
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Shop Talk
Contrary to the beliefs of some truck drivers,
tire pressure cannot be checked with a
hammer.
The only condition a hammer can identify is acompletely deflated tire.
Tire pressures must be checked with a
pressure gauge. In fleets where this is not adrivers responsibility, it must be done by a
technician.
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Shop Talk
Manufacturers of speed
restricted tires, such as the
off-highway lug caution
operators not to exceed the
speed limits and guidelines in
their manuals.
To alert the operator, a decal
located in the cab warns ofthe limitations of speed
restricted tires.
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Shop Talk
Tires are a major fire hazard when trashed
and stored in large quantities.
Once a tire fire has ignited, it can be almost
impossible to extinguish.
Federal and state regulations have made
operators and garages liable for ensuring that
tires are stored and disposed of legally.
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Caution
You cannot learn tire and wheel service
procedure from a book alone.
Before working on tires and wheels make
sure you have received some hands-ontraining.
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Caution
When handling tire assemblies, remember to
lift properly, using your legs rather than your
back.
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Caution
Never raise a vehicle with a jack placed
under a leaf spring.
When the wheel has been raised, use heavy-
duty axle stands placed under the axle anddo not rely on a hydraulic jack alone.
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Shop Talk
The valves used on truck tires are known as
Schrader valves, identical to those used on
cars and bicycles.
It is probably the only common componentfound on all vehicles ranging from a bicycle
to the heaviest off-highway earth moving
equipment.
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Removing Tire Valve Core
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Shop Talk
Disc wheel nuts for right side wheels
generally have right-hand threads, and wheel
nuts for left side wheels usually have left-
hand threads.
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Removing the Tire from a Spoke Wheel
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Removing a Tire from a Disc Wheel
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Caution
Igniting quick start (ether) inside a tire is a
common but dangerous practice used to seat
tire beads.
The explosion that results depends on theproportions of air and ether combined inside
the tire.
Get this mixture wrong and you could injureyourself and others.
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Safety Cage
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Use a Remote In-line Valve
and Gauge When Inflating
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Caution
Watch your fingers and back when installing
tire/rim assemblies onto cast spoke wheels.
It is good practice to wear gloves, and lifting
with the tire/rim behind you is easier on yourback.
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Caution
To check and tighten the inner wheel torque, first
loosen the outer wheel nuts several turns and
tighten the inner nuts, then retighten the outer nuts.
To avoid losing the seating of the outer wheel when
checking the inner wheel torque, loosen alternate
outer nuts, tighten the inner nuts, and retighten the
outer nuts. Then loosen the remaining outer nuts,
tighten inner nuts, and retighten the outer nuts.
OEMs suggest that disc wheels require weekly
inspects and torque checks.
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Torque Sequence for Disc Wheels
U i S
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Using a Square to
Check Dual Tire Matching
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Difference in Tire Size
Typical Dual Mounting
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Typical Dual Mounting
of Cast Spoke Wheel
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Lip-Type Seals
Typical Metal encased
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Typical Metal-encased
Lip-type Seals
Sh T lk
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Shop Talk
If pulling more than one wheel, be sure tokeep all of the components of each wheel
together and separate from the other wheels.
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Caution
Never allow a bearing roller to be spun bycompressed air because the friction that
results can damage the hard surfaced
contact areas.
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Caution
Never use oxy-acetylene torches to heataluminum hubs.
This type of localized heat can weaken and
often destroy the aluminum. If an oven is not available, you should
replace the hub and bearing assembly as a
unit.
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Shop Talk
To ease the installation of the bearing cupinto the hub, the cup can be cooled (by dry
ice or in a freezer), a procedure that stresses
both the bearing cup and hub more evenly. Aluminum hubs are required to be heated in
an oven to get the cup to drop into place.
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Caution
Never pack wet bearings with grease.
Grease coated wheel bearings inhibit the
ability of gear lube to properly lubricate the
bearing assembly.
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Caution
Never hammer or use a punch directly onany part of a seal.
Force must be applied evenly around the
outer edge to avoid cocking the seal. Wheel seals are expensive. Failed wheel
seals are more expensive because of the
labor required to replace them!
Shop Talk
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Shop Talk
The reason dry bearings are seldom used oncurrent equipment is that grease does not
lubricate as effectively as gear oil.
Gear oil has a much wider temperatureoperating range than grease.
Caution
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Caution
Avoid using brass drifts to drive out wheelseals if you plan on reusing the bearing
brass particulate is difficult to remove from a
bearing.
Unitized Hub
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Unitized Hub
Bearing Setting Hardware
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Bearing Setting Hardware
Shop Talk
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Shop Talk
Wheel seal replacements are routine service facilityactivities.
Because of the cost of seals, trainee technicians do
not commonly practice seal replacement in a
training environment.
The first couple of times you replace wheel seals in
a real-world setting, read the instructions and ask
questions. The bottom line is that if you experiencecomeback failures after replacing wheel seals, your
days as a truck technician will not last long.
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Dynamic Balance Weight Chart
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Dynamic Balance Weight Chart
Summary (1 of 7)
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Summary (1 of 7)
Wheels and tires must be properly inspectedduring daily driver inspections and on
preventive maintenance schedules.
Improperly mounted, matched, aligned, orinflated tires create potentially dangerous on-
road situations.
Wheel bearings and wheel seals are key tokeeping the wheel assemblies turning
smoothly and safely.
Summary (2 of 7)
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Summary (2 of 7)
The rim supports the tire. Three general categories of tread design are used
on trucks. Rib tread, general duty lugs, and high-traction lugs
These thread designs are used on bias ply and radialtires.
One wide-base wheel and tire can replace atraditional dual wheel assembly. Wide-base wheels are categorized as high flotation,
super single, wide body, duplex, or jumbo wheels. Compared to steel dual wheel assemblies,
aluminum wide-base wheels and tires aresignificantly lighter in weight.
Summary (3 of 7)
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Summary (3 of 7)
Three basic types of wheels are used in truckapplications: cast spoke, stud-mounted disc, and
hub-mounted disc.
Tires should not be mismatched.
Mismatching includes the mixing of nominal tire sizes
and tread designs on a chassis. It is especially
important that a set of duals never be mismatched.
The tire body and belt material can be constructed
of rayon, nylon, polyester, fiberglass, steel, or the
newest synthetic rubber compounds.
Summary (4 of 7)
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Summary (4 of 7)
All tires (new and retread) sold in the United Statesand Canada must have a DOT number cured into
the lower sidewall on one side of the tire.
Proper tire care and maintenance is second only to
fuel mileage in overall cost per mile of truckoperation.
Improper loading can cause the tires on one side of
the truck or trailer to carry a greater percentage of
the load than those on the other side.
Summary (5 of 7)
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Summary (5 of 7)
Excessive heat produced by running avehicle at higher-than-rated speeds will
shorten tire life.
Wheel balance is the equal distribution ofweight in a wheel with the tire mounted.
Improper wheel bearing adjustment can
result in looseness in the bearings, steering
problems, or serious wheel-off incidents.
Summary (6 of 7)
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Summary (6 of 7)
Technicians should learn and always use theTMC method of adjusting bearings when
working on wheel ends with adjustable
bearings. Preset axle hubs such as the ConMet PreSet
and the Spicer Dana UHS eliminate the need
for the technician to adjust wheel bearings.
These wheel hubs are installed on the axle
and torque to a specified value.
Summary (7 of 7)
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Summary (7 of 7)
Two general categories of wheel seals areused on trucks today.
Lip-type seals and unitized seal assemblies
Wheel seals should always be installed usingOEM seal drivers to avoid damaging them.