Toyota Tacoma 2012, Owner'S Manual

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6-1. Specifications
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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 (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 significantly from the norm due
to variations in driving habits, service practices and differences in
road characteristics and climate.
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Traction AA, A, B, C
The traction grades, from highest to lowest, are AA, A, B and C,
and they 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 braking
(straight ahead) traction tests and does not include cornering
(turning) traction.
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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 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 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.