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09 Wheels and tires
09
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side B-pillar and in the tire inflation table
in this chapter.
•
Cold tires: The tires are considered to be
cold when they have the same tempera-
ture as the surrounding (ambient) air. This
temperature is normally reached after the
vehicle has been parked for at least
3 hours.
Tire specifications – Uniform Tire
Quality Grading
ALL PASSENGER VEHICLE TIRES MUST
CONFORM TO FEDERAL SAFETY
REQUIREMENTS IN ADDITION TO THESE
GRADES.
Quality grades can be found, where appli-
cable, on the tire sidewall between the
tread shoulder and maximum section
width. For example:
Treadwear 200 Traction AA Temperature A
TREADWEAR
The treadwear grade is a comparative rating
based on the wear rate of the tire when tes-
ted under controlled conditions on a specified
government test course. For example, a tire
graded 150 would wear one and one half
(1 ½) times as well on the government course
as a tire graded 100. The relative perform-
ance of tires depends upon the actual condi-
tions of their use, however, and many depart
significantly from the norm due to variation in
driving habits, maintenance practices and dif-
ferences in road characteristics and climate.
TRACTION
The traction grades, from highest to lowest,
are AA, A, B, and C, as measured under con-
trolled conditions on specified government
test surfaces of asphalt and concrete. A tire
marked C may have poor traction perform-
ance. The traction grade assigned to this tire
is based on braking (straight-ahead) traction
tests and is not a measure of cornering (turn-
ing) traction.
WARNING
The traction grade assigned to this tire is
based on braking (straight-ahead) traction
tests and is not a measure of cornering
(turning) traction.
TEMPERATURE
The temperature grades are A (the highest),
B, and C, representing the tire's resistance to
the generation of heat and its ability to dissi-
pate heat when tested under controlled con-
ditions 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 minimum level of perform-
ance that all passenger vehicle tires must
meet under the Federal Motor Safety Stand-
ard No. 109. Grades B and A represent higher
levels of performance on the laboratory test
wheel than the minimum required by law.
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