Transcript Power Point

© Goodheart-Willcox Co., Inc.
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Tire, wheel, and wheel bearing diagnosis
Wheel cover removal and installation
Tire maintenance
Measuring tire and wheel runout
Wheel balance
Mounting and dismounting tires
Tire puncture repair
Wheel bearing service
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Problems usually show up as vibrations,
abnormal tread wear patterns, steering
wheel pull, abnormal noises,
and other symptoms
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Diagnosing Tire Problems
 Inspect
the tires for problems
 Check both sidewalls and the tread area
 If necessary, road test the vehicle to
verify the customer complaint
 Make sure the symptoms are not being
caused by steering, suspension, or front
wheel alignment problems
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Inspecting the Tires
Wiggle the tire to check for dry, rough,
or loose wheel bearings
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Tire Impact Damage
Typical damage found on used tires
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Tire Wear Patterns
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Tire Inflation Problems
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Correct tire inflation is important to the service
life of a tire
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Under inflation
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assures the full tire tread contacts the road
Most tires have a recommended cold inflation
pressure of 1 to 3 pounds-per-square inch (psi)
below the maximum listed air pressure.
wears the outer edges of the tread
sidewalls flex, building up heat
Overinflation
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wears the center of the tread
produces a rough ride
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Tire Inflation Pressure
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Load Index
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Load index
indicates the
maximum load
capacity each tire
is designed to
support. Like
speed ratings,
assume near
perfect operating
conditions to
obtain the ratings
listed in the table
on the left.
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Tire Vibration Problems
 When
one of the front tires is vibrating, it
may be felt in the steering wheel
 When one of the rear tires is vibrating, it
will be felt in the center and rear of the car
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Causes of
Tire Vibration
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Tire Noise
 Thumping
sound caused by ply
separation
 Whine due to abnormal tread wear
 When these noises occur, inspect the
tire for an out-of-round condition or
tread cupping
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these conditions require replacement
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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:
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raise the vehicle on a lift
rotate the tire by hand
feel and listen for bearing roughness
wiggle the tire to check for looseness
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© Goodheart-Willcox Co., Inc.
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Wheel Cover Removal
Pry between the wheel and cover
at 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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 Maintenance
procedures include periodic
inspection, inflation pressure checks, and
tire rotation
 These maintenance steps help ensure
safety and longer tire life
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Checking Tire Inflation Pressure
 Remove
the valve stem cap
 Press the tire gauge squarely over the
stem
 Compare the reading to the maximum
pressure printed on the tire’s sidewall or in
the operator’s manual
 Adjust the pressure as necessary
 Reinstall the cap
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Tire Service
Tools
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Rotating Tires
 Ensures
maximum tire life
 The front and rear tires wear differently
 Rotation helps even out tire wear
 Tires are rotated at specific intervals, such
as every 3000 miles (4827 km)
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Tire Rotation Patterns
BIAS TIRES
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RADIAL TIRES
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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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Torquing Lug Nuts
Torque the nuts to specifications in a
crisscross pattern
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 Tire
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runout
caused by ply separation or manufacturing
defect
 Wheel
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runout
caused by impact damage or incorrect
welding of the spider and rim
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Lateral Runout
 Side-to-side
movement of a wheel or
tire
 Maximum for a tire
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0.090" (2.0 mm)
 Maximum
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for a wheel
0.045" (1.0 mm)
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Measuring Lateral Runout
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Mount a dial indicator with the stem against
the sidewall and side of the rim
 Check the reading at several points
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Radial Runout
 Difference
in radius from the center axis
of rotation (out-of-round)
 Maximum for a tire
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0.060" (1.5 mm)
 Maximum
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for a wheel
0.035" (0.9 mm)
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Measuring Radial Runout
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Mount a dial indicator with the stem against
the tread and the lip of the rim
 Check the reading at several points
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 Improper
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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Static Imbalance
Caused by a heavy spot located in
the center of the tire tread
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Dynamic Imbalance
The heavy spot is to one side of
the tread or on the sidewall
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Wheel Balancing
 Wheels
are balanced by adding wheel
weights
 Most weights are press-fit onto the wheel
 Weights for some mag wheels stick onto
the wheel with an adhesive backing
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Wheel Balancing
 Static
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balancing
add weights opposite the heavy area of the
wheel
if a large amount is needed, add half to the
inside and half to the outside of the wheel
 Dynamic
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balancing
add weights exactly where needed
the dynamic balancing machine will
indicate where weight must be added
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Wheel Balancing
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On-Car Balancing
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Follow the equipment operating instructions
Wear eye protection
Remove rocks and debris from the tread
Place the vehicle on a jack stand
When using the engine to spin the drive wheels,
do not exceed 35 mph
(40 to 56 km/h)
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when one wheel is on the floor, the free wheel will
turn at twice the indicated speed
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On-Car Balancing
With a limited-slip differential, raise both
rear wheels off the floor
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Wheel Balancers
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A wheel balancing machine is used to determine
which part of a wheel assembly is heavy
 Bubble balancer
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Off-car balancer
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static balance
static or dynamic balance
On-car balancer
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static or dynamic balance
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Bubble Balancer
The wheel and tire assembly is mounted
on the machine
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Bubble Balancer
Add weights until the bubble is centered
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Off-Car Balancer
 The
wheel and tire assembly is mounted
on the machine and rotated
 The machine will indicate where weights
should be added
 After adding weights, spin the tire again to
check for vibration
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Off-Car Balancer
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On-Car Balancer
 Provides
an electric motor to spin the
wheel and tire assembly
 An electronic pick-up unit or a handoperated device is used to determine
where weights are needed
 Balances the wheel cover, brake disc, and
lug nuts, along with the tire and wheel
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 A tire
changing machine is used to force
the tire on and off the wheel
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prevents tire or rim damage
reduces the labor required
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Tire Changing Machine
Power head turns the bar to force the
beads over the rim
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Tire Changing Machine
Applies tremendous force to stretch the
tire bead on and off the wheel
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Safe Work Practices
 Wear
eye protection
 Keep your fingers out of the way
 Never mount a tire on a rim that is not
smooth and clean
 Always lubricate the bead and wheel
flange with the proper lubricant
 Only inflate a tire on the machine or in a
safety cage, as recommended
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Safe Work Practices
 Stand
away from the tire when adding air;
a loud “pop” sound will indicate when the
beads seat
 Do not exceed 40 psi (276–345 kPa)
when initially inflating a tire
 After inflation, install the core and inflate
the tire to the recommended pressure
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Finding/Repairing a Leak
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Inflate the tire with air
Place the tire in a drum of water, or wet the tire
with a water hose
Look for air bubbles forming on the tire or around
the bead at the rim
Bubbles indicate leakage
Mark the leak with a crayon or chalk
Puncture must be in the tread to be repairable
There must be adequate tread left on the tire to
be repairable
Punctures through the tread can be repaired with
a plug if they are not too large, but punctures to
the sidewall should not be repaired.
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Wheel bearings are normally filled with grease
Modern Vehicles usually do not have
serviceable wheel bearings
If the grease dries out, the bearing will fail
Some bearings on older vehicles are serviceable
Most newer bearings are sealed units
Wheel bearings on front-wheel –drive
vehicles are difficult to service and require
special methods or tools.
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Nondriving Hub and Tapered
Roller Wheel Bearing
Assembly
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Bearing Inspection
Wash and dry the bearings
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Bearing Inspection
Bearing and
race problems
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Greasing the Bearings
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Serviceable disc-brake wheel bearings require a
special grease called high-temperature wheelbearing grease
 Use a packer or grease the bearing assemblies by
hand
 Make sure the grease is worked completely through
each bearing cage and around every ball or roller
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Greasing the
Bearings
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Driving Hub and Wheel Bearing
Assembly
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Rear Hub Assembly
(Non-serviceable)
If bearings are dry and noisy, remove and
replace the entire assembly
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