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),
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 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.
Traction -- A, B, C
The traction grades, from highest to lowest, are A, B,
and C, and they represent the tire’s ability to stop on
wet pavement as measured under controlled conditions
on 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 (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.
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