Uniform Tire Quality Grading
The following information relates to the system developed by the United States National Highway
Traffic Safety Administration, which grades tires by
treadwear, traction and temperature performance. (This
applies only to vehicles sold in the United States.) The
grades are molded on the sidewalls of most passenger
car tires. The Uniform Tire Quality Grading system does
not apply to deep tread, winter-type snow tires,
space-saver or temporary use spare tires, tires with
nominal rim diameters of
10 to 12 inches (25 to 30 cm),
Treadwear
The treadwear grade is a comparative rating based on
the wear rate
of the tire when tested under controlled
conditions
on a specified government test course. For
example, a tire graded
150 would wear one and a half 1
(1 1/2) 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 significantly from the norm due to variations
in driving habits, service practices and differences in
road characteristics and climate.
I.
or to some limited-production tires. ;,*?;;x.,< .
. .'-I '.'Traction -- A, B, C
While the tires available on General Motors passenger 1
cars and light trucks may vary with respect to these The traction grades, from highest to lowest, are A, B, and
grades,, they must also conform to Federal safety
C, and they represent the tire's' ability to stop on wet
requirements and additional General Motors Tire pavement as measured under controlled conditioa
on
Peiformance Criteria (TPC) standards. specified 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 braking (straightahead) traction tests and does not
include cornering (turning) traction.
6-53
ProCarManuals.com
Temperature -- A, B, C
The temperature grades are A (the highest), B, and C,
representing he 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
hgh 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
€3 and A represent higher levels of performance on the
laboratory test wheel than the minimum required by law.
Warning: ne 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.
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 *at 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
Pontiac dealer if any
of these conditions exist.
ProCarManuals.com
