Chevrolet 1993 Astro Passenger Owner's Manual page 286

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
lire
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 out, replace it (except some aluminum wheels, which can
sometimes be repaired). See your GM 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.
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 you have the right wheel, wheel bolts, and wheel nuts for your
vehicle.
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