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TIRE KNOW-HOW
Tool and Material Checklist:
- Pocket pressure gauge
- Antitheft wheel lug nut key
- Air compressor
- Sponge
- Wheel shocks
- Soap
- Jack and Jack stand
- Crayon
- Tread depth Indicator
- Plug repair kit
- Key wrench
Tires perform two important functions. First,
they provide frictional contact between the wheels
and the road so that good traction Is assured. This
allows for rapid acceleration, offers resistance to
the normal tendency of the car to skid on turns,
and permits quick stops when the brakes are applied. Second, they provide a cushion between the
road and the wheels to absorb the shock as bumps
are encountered. Tires should not be taken for
granted: check them regularly for proper inflation
pressure, wear, and damage.
INFLATION PRESSURE
Without a doubt, neglect ruins more tires than
anything else. For long tire life, riding comfort, and
handling stability, keep your tires properly inflated.
Underinflatlon
Too little air pressure can result in excessive tire
heat, abnormal wear, poor handling, and reduced
fuel economy. An under-inflated tire will show maximum wear on the outside edges of the tire tread,
with little or no wear in the center.
Overinfiation
Too much air pressure can cause a poor ride
and handling, as well as increased susceptibility to
road impact damage. An over-inflated tire will show
its wear in the center of the tread and little wear on
the outside edges.
Making a Pressure Check
Tire pressure should be checked at least once a
month (preferably more often) and always when the tires are cold. Cold tire ratings are applicable
when a vehicle has been parked for 3 hours or
more or driven less than a mile. Even a short drive
can heat tip the tires sufficiently to defeat the purpose of the check. For this reason, it is a good idea
to purchase your own pocket pressure gauge and
carry it in the glove compartment, This type of
gauge is generally more accurate than those found
in service stations.
Make a pressure check as follows:
1. Look up the Inflation pressure recommended
by the vehicle manufacturer. It is indicated either
on a decal located in the glove compartment or on
the left front vehicle door or in your owner's manual. However, keep in mind that the vehicle
manufacturer normally specifies a pressure designed to
provide a smooth ride at the expense of tire wear.
Instead, you might want to use the pressure specified by the tire manufacturer, since it is geared
toward maximum tire wear and performance. This
recommended pressure can be found on the tire
itself.
2. Remove the valve cap from the valve stem
(assuming a valve cap is used).
3. Use a pressure gauge to check the pressure.
Do not rely solely on the appearance of the tire; it
can be deceiving. For example, while bias-belted
tires look firm when they are inflated, radials tend
to look a little on the soft side.
4. If necessary, add air. You might want to consider buying a small air compressor to do this job
quickly and easily.
5. Reinstall the valve cap to prevent dirt and
moisture from entering the valve core, which could
cause leakage.
Special Circumstances
For sustained driving at highway speeds, cold inflation should be increased about 4 psi but should
not exceed the following levels:
- 32 psi for load range B
- 36 psi for load range C
- 40 psi for load range D
A change in tire pressure will occur with the
onset of cold weather. Every 10-degree drop in
temperature causes the pressure to decrease
about 1 psi. Adjust the pressure accordingly, then
bleed off the excess air when the weather gets
warmer.
NOTE: Never bleed a hot tire. Bleeding only
serves to increase the flexing action of the tire,
which can result in damage or failure. When carrying heavier-than-normal loads, tire pressure
should be increased-but never to an extent that is
greater than the load range.
TIRE ROTATION
To equalize wear, most car and tire manufacturers recommend that the tires be rotated.
Remember that front and rear tires perform different
jobs and can wear differently, depending on driving habits and the type of vehicle. In a
rear-wheel-drive vehicle, for instance, the front tires usually
wear along the outer edges because of the scuffing and slippage encountered In cornering; the
rear tires wear in the center because of acceleration thrusts. Bias-ply and bias-belted tires should
be rotated about every 6,000 miles. Radial tires
should be rotated at the first 7,500 and then at
least every 15,000 miles thereafter. In the event of
abnormal wear, find and correct the cause, then
rotate the tires to promote more even wear. If the
vehicle is equipped with a compact spare, do not
include it in the rotation of the other four tires.
When installing snow tires, the regular tread
tires on the rear should be moved to the front and
the front tires stored. When the snows are removed, install the stored tires on the rear. Do not
rotate studded tires; always remount them in their
original positions.
NOTE: Snow tires installed on the rear require a
4 psi increase in the cold inflation pressure above
that shown on the tire pressure decal, but should
not exceed the maximum cold inflation pressure
marked on the tire.
TREAD WEAR
Tire rotation provides an excellent opportunity
to check for potentially dangerous conditions. Abnormal or excessive wear can be caused by an
incorrect wheel/tire imbalance or improper tire
pressure.
Most tires today have built-in tread wear indicators to show when they need replacement. These
indicators will appear as 1/2"-wide bands when the
tread depth becomes 1/16". When the indicators
appear in two or more adjacent grooves at three
locations around the tire, or when cord or fabric is
exposed, tire replacement is recommended.
If a tire does not have tread wear indicators, a
tread depth gauge quickly shows in 32nds of an
inch how much of a tire's tread is left. When only
2/32" is left, It is time to replace the tire.
REPLACING TIRES
When replacing tires, keep In mind the following
tips from the Tire Industry Safety Council:
1. Tires should always be replaced with the
same size designation or an approved option size
as recommended by the auto or tire manufacturer.
Use of any other size or type tire might seriously
affect ride, handling, speedometer/odometer calibration, vehicle ground clearance, and tire
clearance to the body and chassis.
2. When replacing original tires with an optional
recommended size of different diameter, the speedometer must be recalibrated by installing the
correct speedometer-driven gear.
3. To achieve the best all-around vehicle performance, bias-belted tires and bias tires should
not be mixed on the same car.
4. Do not use radial tires with other types, such
as bias or bias belted, except for short-term, low speed emergency use. Use only radial snow tires
with radial-ply tires.
5. New tires should be Installed in pairs on the
same axle. When replacing only one tire, it should
be paired with the tire having the least wear, to
equalize braking traction. Also, choose the same
brand and model tire as the one It is being paired
with; dissimilar tires can cause serious problems
during panic braking.
6. When buying new tires, be sure the seller records your name, address, and tire identification
number as required by federal law.
REPLACING WHEELS
Before attempting to remove or replace a wheel
when changing a flat tire or rotating tires, be sure
to
1. Park the car on a level surface and set the
parking brake.
2. Set the automatic transmission in PARK and
block the tires so the vehicle does not roil.
3. If you are on a highway, activate the hazard
warning flasher.
After removing the spare wheel and tire, jack,
jack stand, and wrench from the trunk, proceed
with changing the wheel as follows:
1, Remove the wheel cover. Keep in mind that
some wheel covers are equipped with an antitheft
locking system. The lock bolt for each wheel cover
is located behind the hub ornament. A special key
wrench is required to pry off the hub ornament
and remove the lock bolt. In the event the key is
misplaced, a master key set is available at the
dealer.
2. Loosen, but do not remove, the hub lug nuts.
In recent years more and more wheels are being
equipped with antitheft wheel lugs (one per
wheel). The key has a circular keyway that is
matched to the female slot in the antitheft wheel
lug nut. To loosen the antitheft wheel lug nut, inset the key into the slot, place the lug nut wrench
on the key, and, while applying pressure on the
key, loosen the lug nut.
3. Jack up the car as directed in the owner's
manual, Always operate the jack with a slow,
smooth motion. Raise the vehicle so the tire just
clears the ground.
4. Remove all iu9 nuts or bolts and put them in
the wheel cover. Take off the wheel.
5. Put the new wheel on and tighten the lug nuts
or bolts slightly.
6. Lower the jack and tighten all the lug nuts or
bolts securely using the recommended tightening
sequence. If a torque wrench is available, tighten
the lug nuts to the specified torque.
7. Check and adjust the air pressure in all the
tires.
TIRE REPAIR
The most common tire repair problem is a puncture. When properly replaced, a punctured tire can
be put back in service safely without fear of the
leak recurring. Service punctures in the tread area
only; never attempt to repair punctures in the tire
shoulders or sidewalls. In addition, do not service
a tire that has sustained the following damage:
- Bulges or blisters
- Ply separation
- Broken or cracked beads
- Fabric cracks or cuts
- Wear down to the fabric or visible wear
indicators
- Punctures larger than 1/4" diameter
NOTE: Tire sealants that are injected through
the valve stem must not be used to service punctured tires because they can promote wheel rust
and tire imbalance.
Locating Punctures
1. Inflate the tire to its maximum inflation pressure (marked on the tire).
2. Submerge the wheel/tire assembly in a tank
of water, or sponge on a soapy water solution. The
water or soapy solution will bubble at the exact
spot of the leak.
3. Mark the location of the leak with a crayon so
that it can be easily found once the tire is removed
from the wheel.
4. Use a crayon to mark the valve stem location
on the tire so that the original balance and runout
can be maintained when the tire is remounted.
A tire should always be mounted or dismounted
with a tire changer. This can be done at a service
station. Once the tire is removed from the wheel
and the cause of the puncture has been eliminated, the tire can be serviced from the inside
using a combination plug and vulcanized patch. Although the service kit manufacturers instructions
should always be heeded, following are some
general recommendations.
CAUTION: Large holes (more than 1/8" In diameter) In radial tires should be patched Instead of
plugged. Large plugs can damage the carcass of a radial tire.
Plug Repairs
1. After removing the cause of the puncture and
reaming the damaged area, place a plug slightly
larger than the size of the puncture in the eye of
the insertion tool. Wet both the plug and insertion
tool with vulcanizing fluid.
2. While holding and stretching the long end of
the plug, insert it Into the puncture hole from inside the tire. The plug must extend above both the
tread and inner liner surface, If the plug pops
through, discard it and repeat the insertion
procedure.
3. Once the insertion tool has been removed,
trim off the plug 1/32" above the inner liner surface. Do not pull on the plug while cutting.
NOTE: Dismounting the tire from the rim is not
always necessary when plugging a tire, It the
source of the leak is obvious, the repair can be
done from the outside of the tire; in many cases
the wheel doesn't even have to be removed.
Cold Patching
1. After buffing and cleaning the tire, carefully
remove the backing from the patch.
2. Spread vulcanizing fluid over the punctured
area and let it dry.
3. Center the patch over the puncture.
4. Run a stitching tool over the patch to help
bind it to the tire.
NOTE: When repairing radial tires, only a specially approved radial patch should be used. These
patches have arrows that must be lined up parallel
to the radial plies.
Hot Patching
This is very similar to a cold patch. The only difference is that the hot patch is clamped over the
puncture and heat is applied to make it adhere.
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