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Tires
Vehicle care and maintenance 9-15
9
EXAMPLE: DOT MA L9 ABCD
1504
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
(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 signifi-
cantly from the norm due to variations in
driving habits, service practices and differ-
ences in road characteristics and climate.
The traction grades, from highest to lowest,
are AA, A, B and C. Those 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.
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 corre-
sponds to a level of performance which all
passenger car tires must meet under the Fed-
eral 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.
N00939302008
Proper tire inflation pressure is essential for
the safe and satisfactory operation of your
vehicle. The wrong tire pressure will cause
problems in three major areas:
Safety
Too little pressure increases flexing in the
tire and can cause tire failure. Too much
pressure can cause a tire to lose its ability
to cushion shock. Objects on the road and
potholes could then cause tire damage that
may result in tire failure.
DOT
Department of Transporta-
tion
This symbol certifies that the
tire is in compliance with the
U.S. Department of Trans-
portation tire safety stan-
dards, and is approved for
highway use.
MA
Code representing the tire
manufacturing location.
(2 digits)
L9
ABC
D
Code representing the tire
size. (2 digits)
Code used by tire manufac-
turer. (1 to 4 digits)
15
Number representing the
week in which the tire was
manufactured. (2 digits)
04
Number representing the
year in which the tire was
manufactured. (2 digits)
Treadwear, Traction and Temper-
ature Grades
Treadwear
Traction
Temperature
Tire inflation pressures
BK0277700US.book 15 ページ ２０１９年３月８日 金曜日 午前９時２３分
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