Pontiac 1993 Sunbird Owner's Manual page 180

heat and its ability to dissipate heat
when tested under controlled
conditions on a specified 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 inflated and not overloaded.
Excessive speed, underinflation, or
excessive loading, either separately or in
combination, can cause heat buildup
and possible tire failure.
These grades are molded on the
sidewalls of passenger car tires.
While the tires available as standard or
optional equipment on General Motors
vehicles may vary with respect to these
grades, all such tires meet General Motors
performance standards and have been
approved for use on General Motors
vehicles. All passenger type (P Metric)
tires must conform to Federal safety
requirements in addition to these grades.
Wheel Alignment and Tire
Balance
The wheels on your vehicle were
aligned and balanced carefully at the
factory to give you the longest tire life
and best overall performance.
In most cases, you will not need to have
your wheels aligned again. However, if
you notice unusual tire wear or your
vehicle pulling one way or the other, the
alignment may need to be reset. If you
notice your vehicle vibrating when
driving on a smooth road, your wheels
may need to be rebalanced.
Wheel Replacement
Replace any wheel that is bent, cracked
or badly rusted. 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 Pontiac
dealer if any of these conditions exist.
Your dealer will lmow 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.
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
Pontiac model.