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Uniform Tire Qualify 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
Yz)
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
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.
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 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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