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
3bility to dissipate heat when tested under
:ontrolled 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 separately ,,or
in combination, can cause heat buildup
and possible tire failure.
Those 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.
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