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9-78 Vehicle Care
Uniform Tire Quality
Grading
Quality grades can be found
where applicable on the tire
sidewall between tread shoulder
and maximum section width.
For example:
Treadwear 200 Traction AA
Temperature A
The following information relates
to the system developed by the
United States National Highway
Traffic Safety Administration
(NHTSA), 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 (UTQG) system
does not apply to deep tread,
winter-type snow tires,
space-saver, or temporary use
spare tires, tires with nominal
rim diameters of 25 to 30 cm
(10 to 12 inches), or to some
limited-production tires.
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
specified 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 significantly from the
norm due to variations in
driving habits, service practices,
and differences in road
characteristics and climate.