Chevrolet 2011 Volt Owner's Manual page 395

All Passenger Car 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
a half (1½) 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 AA, A, B, C
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.
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 A, B, C
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
Vehicle Care
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 car tires must meet
under the Federal Motor
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, underinflation, or
excessive loading, either
separately or in combination,
can cause heat buildup and
possible tire failure.
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