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SERVICING AND MAINTENANCE
250
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 cate-
gory 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 government course as a
tire graded 100. The relative perfor-
mance 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 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.
STORING THE VEHICLE
If the vehicle is left inactive for longer than a
month, the following precautions should be
observed:
Park the vehicle in an area that is covered
and dry, and well-ventilated if possible.
Slightly open the windows.
Check that the Electric Park Brake is not
activated.
Carry out the procedure: “manual trunk
opening device” procedure described in this
paragraph.
Disconnect the negative battery terminal
and check the battery charge. Repeat this
check once every three months during
storage.
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,
under-inflation, or excessive loading, either
separately or in combination, can cause
heat buildup and possible tire failure.
21_GA_OM_EN_USC_t.book Page 250
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