Volvo 2013 XC70 - Manual (Page 307)

08 Wheels and tires
Uniform Tire Quality Grading
08
305
Quality grading information
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 tested
under controlled conditions on a specified gov-
ernment test course. For example, a tire gra-
ded 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 signifi-
cantly 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 sur-
faces of asphalt and concrete. A tire marked C
may have poor traction performance. The trac-
tion grade assigned to this tire is based on
braking (straight-ahead) traction tests and is
not a measure of cornering (turning) 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 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 minimum level of performance that all pas-
senger vehicle tires must meet under the Fed-
eral 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 estab-
lished for a tire that is properly inflated and
not overloaded. Excessive speed, under-
inflation, or excessive loading, either sepa-
rately or in combination, can cause heat
buildup and tire failure.