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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
manufacturer in each category is
shown on the sidewall of the tires
on your vehicle.
All passenger vehicle tires must
conform to Federal safety
requirements 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 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 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 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 straight-ahead
braking traction tests, and does
not include acceleration,
cornering, hydroplaning, or peak
traction characteristics.
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
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
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 temperature grade for this tire
is established for a tire that is
properly inflated and not
overloaded. Excessive speed,
under-inflation, or excessive
loading, either separately or in
combination, can cause heat
buildup and possible tire failure.
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