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.)
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. 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.
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: 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
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