Volvo 2005 C70 - Manual (Page 93)

87
Wheels and tires
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
applicable, 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 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 many depart
significantly from the norm due to variation in
driving habits, maintenance practices and
differences in road characteristics and climate.
TRACTION
The traction grades, from highest to lowest,
are AA, A, B, and C, as measured under
controlled conditions on specified government
test surfaces of asphalt and concrete. A tire
marked C may have poor traction
performance. 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 AA (the highest),
A, 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 temper-ature can
lead to sudden tire failure. The grade C
corresponds to a minimum level of
performance that all passenger vehicle 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 traction grade assigned to this tire is
based on braking (straight-ahead) traction
tests and is not a measure of cornering
(turning) traction.
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 tire failure.