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271
DEPARTMENT OF
TRANSPORTATION UNIFORM
TIRE QUALITY GRADES
The following tire grading categories were
established by the National Highway
Traffic Safety Administration. The specific
grade rating assigned by the tire's manu-
facturer in each category is shown on the
sidewall of the tires on your vehicle.
All passenger vehicle tires must
conform to Federal safety require-
ments in addition to these grades.
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 one-half times as well on the govern-
ment course as a tire graded 100. The rela-
tive 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 prac-
tices, and differences in road characteris-
tics and climate.
Traction Grades
The Traction grades, from highest to
lowest, are AA, A, B, and C. These
grades represent the tire's ability to
stop on wet pavement, as measured
under controlled conditions on speci-
fied government test surfaces of
asphalt and concrete. A tire marked C
may have poor traction performance.
Temperature Grades
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 condi-
tions 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 corre-
sponds to a level of performance, which
all passenger vehicle 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 traction grade assigned to this tire is
based on straight-ahead braking traction
tests, and does not include acceleration,
cornering, hydroplaning, or peak traction
characteristics.
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.
20_GA_OM_EN_USC_t.book Page 271
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