GMC 1993 Jimmy Owner's Manual page 311

Warning: The traction grade assigned to this tire is based on braking
(straight-ahead) traction tests and does not include cornering (turning) traction.
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 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 separate19 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.
I f
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 i f 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.
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