342 SERVICING AND MAINTENANCE
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.
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 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.
21_WD_OM_EN_USC_t.book Page 342
To Next Page
Loading...
