66 Tire and Wheel Bearing FundamentalsII (1)
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Transcript of 66 Tire and Wheel Bearing FundamentalsII (1)
© Goodheart-Willcox Co., Inc.
Tires perform two basic functions: act as a soft cushion between the road
and the metal wheel provide adequate traction (friction) with
the road surface
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Tire Types Pneumatic
filled with air internal air pressure pushes out on the
inside of the tire to support the vehicle Tubeless tire
does not use an inner tube tire and wheel form an airtight unit
Tube-type tire uses an inner tube to hold air pressure
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Bias Ply Tire Plies run on an angle from bead to
bead Angle is reversed from ply to ply Does not use belts Body of the tire flexes easily Provides a smooth ride Plies and tread are weakest
reduces traction at high speeds increases rolling resistance
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Radial Ply Tire Plies run straight across from bead to
bead Stabilizer belts lie beneath the tread Belts can be made of steel, flexten,
fiberglass, or other materials
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Radial Ply Tire Uses a very flexible sidewall with a stiff
tread provides a very stiff footprint improves safety, cornering, braking, and
wear may produce a harsher ride at low speeds
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Tire Size
Alpha-Numeric–Uses letters and numbers to denote tire size in inches and its load-
carrying capacity in pounds
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Tire Size
P= passenger LT=Light Truck ST= Special Trailer T= Temporary C= Commercial
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Aspect Ratio
Height-to-width ratio of a tire. Comparison of a tire’s height and width
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Tread Plies Number of plies and ply rating:
2-ply 2-ply with a 4-ply rating 4-ply
Ply rating doesn’t mean how many plies the tire has Plies are made of different materials today
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Maximum Load Rating Amount of weight the tire can carry at
the recommended inflation pressure Printed on the sidewall P-metric:
given in kilograms and pounds Alpha-numeric:
indicated by a letter such as B, C, or D
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Maximum Inflation Pressure
Highest air pressure that should be pumped into the tire
Many tires have a maximum recommended pressure of 32 to 40 psi (220 to 275 kPa)
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Checking Tire Inflation Pressure
Check the manufactures recommended tire pressure In Door Jam In owners manual
Compare to max inflation and inflate to proper inflation
Many of today's cars have to be inflated to manufactures specs
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DOT Serial Number Identifies the manufacturer, plant,
location, construction, and date of manufacture
Stamped into the sidewall Department of Transportation rating
means the tire has passed prescribed safety tests
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Speed Rating Maximum allowable sustained road
speed a tire can safely withstand without failure
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Traction Rating Traction rating is a letter based on a
straight-line wet surface braking test AA- (Best) A B C- (Worst)
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Tread Wear Higher the number the better the tread
wear Tread wear rating 200 will last 2 times as
long as a 100
Can not compare different manufactures tread wear ratings
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Heat Rating A- Best (coolest running tire)
B-
C- Least able to dissipate heat
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Wear Bars
When too much tread has worn
away, solid rubber bars will show up across the tread
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Rotating Tires Ensures maximum tire life Front and rear tires wear differently Rotation helps even out tire wear Tires are rotated at intervals such as
every 3000 miles (5000 km)
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Today’s Preferred Pattern
This Pattern is used today because of radial tire memory!
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Compact Spare Tire
This is a high pressure spare, requiring60 psi (415 kPa)
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Self-Sealing Tire Action
A. Nail punctures tireB. Nail is pulled outC. Sealing compound
flows into the hole
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Run-Flat Tires Use extremely stiff sidewall
construction Still usable with a loss of air pressure Tire will still retain most of its shape
because the sidewall is strong enough to support vehicle weight
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Retreads Used tires that have had a new tread
vulcanized to the old carcass, or body Large truck tires are often recapped
because of the high cost of new truck tires
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Tire Inflation Monitoring System
Often used with run-flat tires Pressure sensors are mounted on each
wheel If tire pressure is not correct, the wheel
sensor produces a radio signal Signal is received by a module that
turns on a dash warning light
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ABS Tire Monitoring Wheel speed is
measured using ABS sensors
Different wheel speeds equals uneven tire pressures
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Valve Stem Assembly
Valve stem snaps into the holein the wheel
Press fit forms an airtight seal
Valve core screws into the
valve stem body
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Lug Nut and Stud
Stud is pressed into the hub or
axle flange
If metric or left-hand threads are used,
markings will normally be given
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Torquing Lug Nuts Torque is very important, especially on
vehicles with mag wheels and lightweight hubs
Overtorquing can cause wheel and hub distortion, or brake pulsation
Undertorquing might allow the lug nuts to loosen and the wheel to fall off
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Wheel Cover Removal
Pry between the wheel and coverat four alternating points
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Wheel Cover Installation
Hold the wheel cover in place with the valve stem sticking through the cover
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Wheel balance is a common cause of tire and steering wheel vibration
When one side of a tire is heavier than the other, centrifugal force tries to throw the heavy side outward when the tire is rotating
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Ball Bearing
Balls allow parts to rotate with a minimum amount of friction and wear
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Hub and Wheel Bearing
(Four-Wheel Drive)
Front axle, brakes, hub, and wheel bearing assembly
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Wheel Bearing Noise Produced by a dry, worn wheel bearing When balls or rollers are damaged from
lack of lubrication, they may emit a humming or growling sound
Checking the bearings: raise the vehicle on a lift rotate the tire by hand feel and listen for bearing roughness wiggle the tire to check for looseness