
While the tires available on General Motors
passenger cars and light trucks may vary with
respect to these grades, they must also conform
to federal safety requirements and additional
General Motors Tire Performance Criteria (TPC)
standards.
Treadwear
The treadwear grade is a comparative rating based
on the wear rate of the tire when tested under
controlled conditions on a speci ed government
test course. For example, a tire graded 150 would
wear one and a half (1.5) times as well on the
government course as a tire graded 100. The
relative performance of tires depends upon the
actual conditions of their use, however, and may
depart signi cantly from the norm due to variations
in driving habits, service practices, and differences
in road characteristics and climate.
Traction – AA, A, B, C
The traction grades, from highest to lowest, are AA,
A, B, and C. Those grades represent the tire’s
ability to stop on wet pavement as measured under
controlled conditions on speci ed government test
surfaces of asphalt and concrete. A tire marked C
may have poor traction performance.Warning:The traction grade assigned to this
tire is based on straight-ahead braking traction
tests, and does not include acceleration, cornering,
hydroplaning, or peak traction characteristics.
Temperature – A, B, C
The temperature grades are A (the highest), B,
and C, representing the tire’s resistance to the
generation of heat and its ability to dissipate heat
when tested under controlled conditions on a
speci ed indoor laboratory test wheel. Sustained
high temperature can cause the material of the tire
to degenerate and reduce tire life, and excessive
temperature can lead to sudden tire failure. The
grade C corresponds to a level of performance
which all passenger car tires must meet under the
Federal Motor Vehicle Safety Standard No. 109.
Grades B and A represent higher levels of
performance on the laboratory test wheel than
the minimum required by law.
Warning:The temperature grade for this tire is
established for a tire that is properly in ated
and not overloaded. Excessive speed,
underin ation, or excessive loading, either
separately or in combination, can cause heat
buildup and possible tire failure.
421

Wheel Alignment and Tire Balance
The tires and wheels on your vehicle were aligned
and balanced carefully at the factory to give you
the longest tire life and best overall performance.
Adjustments to wheel alignment and tire balancing
will not be necessary on a regular basis. However,
if you notice unusual tire wear or your vehicle
pulling to one side or the other, the alignment may
need to be checked. If you notice your vehicle
vibrating when driving on a smooth road, your tires
and wheels may need to be rebalanced. See your
dealer for proper diagnosis.
Wheel Replacement
Replace any wheel that is bent, cracked, or badly
rusted or corroded. If wheel nuts keep coming
loose, the wheel, wheel bolts, and wheel nuts
should be replaced. If the wheel leaks air, replace
it (except some aluminum wheels, which can
sometimes be repaired). See your dealer if any
of these conditions exist.
Your dealer will know the kind of wheel you need.
Each new wheel should have the same
load-carrying capacity, diameter, width, offset
and be mounted the same way as the one
it replaces.
422

If you need to replace any of your wheels, wheel
bolts, or wheel nuts, replace them only with new
GM original equipment parts. This way, you will be
sure to have the right wheel, wheel bolts, and wheel
nuts for your vehicle.
{CAUTION:
Using the wrong replacement wheels,
wheel bolts, or wheel nuts on your vehicle
can be dangerous. It could affect the
braking and handling of your vehicle,
make your tires lose air and make you
lose control. You could have a collision
in which you or others could be injured.
Always use the correct wheel, wheel bolts,
and wheel nuts for replacement.Notice:The wrong wheel can also cause
problems with bearing life, brake cooling,
speedometer or odometer calibration, headlamp
aim, bumper height, vehicle ground clearance,
and tire or tire chain clearance to the body and
chassis.
SeeChanging a Flat Tire on page 428for more
information.Used Replacement Wheels
{CAUTION:
Putting a used wheel on your vehicle is
dangerous. You cannot know how it has
been used or how far it has been driven. It
could fail suddenly and cause a crash. If
you have to replace a wheel, use a new
GM original equipment wheel.
423

Tire Chains
{CAUTION:
Do not use tire chains. There is not enough
clearance. Tire chains used on a vehicle
without the proper amount of clearance
can cause damage to the brakes,
suspension, or other vehicle parts. The
area damaged by the tire chains could
cause you to lose control of your vehicle
and you or others may be injured in a
crash.
CAUTION: (Continued)
CAUTION: (Continued)
Use another type of traction device only if
its manufacturer recommends it for use
on your vehicle and tire size combination
and road conditions. Follow that
manufacturer’s instructions. To help avoid
damage to your vehicle, drive slowly,
readjust or remove the device if it is
contacting your vehicle, and do not spin
the wheels. If you do nd traction devices
that will t, install them on the front tires
for front-wheel-drive vehicles. If your
vehicle has all-wheel drive, install traction
devices on either the front tires or all four
tires, but never on the rear tires only.
424

If a Tire Goes Flat
It is unusual for a tire to blowout while you are
driving, especially if you maintain your vehicle’s
tires properly. If air goes out of a tire, it is much
more likely to leak out slowly. But if you should ever
have a blowout, here are a few tips about what to
expect and what to do:
If a front tire fails, the at tire will create a drag that
pulls the vehicle toward that side. Take your foot off
the accelerator pedal and grip the steering wheel
rmly. Steer to maintain lane position, and then
gently brake to a stop well out of the traffic lane.A rear blowout, particularly on a curve, acts much
like a skid and may require the same correction you
would use in a skid. In any rear blowout remove
your foot from the accelerator pedal. Get the vehicle
under control by steering the way you want the
vehicle to go. It may be very bumpy and noisy, but
you can still steer. Gently brake to a stop, well off
the road if possible.
{CAUTION:
Lifting a vehicle and getting under it to
do maintenance or repairs is dangerous
without the appropriate safety equipment
and training. The jack provided with your
vehicle is designed only for changing a
at tire. If it is used for anything else, you
or others could be badly injured or killed
if the vehicle slips off the jack. Use the
jack provided with your vehicle only for
changing a at tire.
If a tire goes at, the next part shows how to use the
jacking equipment to change a at tire safely.
427