Volvo S80 Owner's Manual page 227

06 Maintenance and specifications
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 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 government test course. For exam-
ple, a tire graded 150 would wear one and
one half (1 1/2) times as well on the govern-
06
ment course as a tire graded 100. The rela-
tive 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 character-
istics and climate.
TRACTION
The traction grades, from highest to lowest,
are AA, A, B, and C, as measured under con-
226
trolled conditions on specified government
test surfaces of asphalt and concrete. A tire
marked C may have poor traction perfor-
mance. The traction grade assigned to this
tire is based on braking (straight-ahead) trac-
tion 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 AA (the highest),
A, B, and C, representing the tire's resistance
to the generation of heat and its ability to dis-
sipate 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 tempera-
ture can lead to sudden tire failure. The grade
C corresponds to a minimum level of perfor-
mance that all passenger vehicle tires must
meet under the Federal Motor Safety Stan-
dard No. 109. Grades B and A represent
higher levels of performance on the labora-
tory 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-in-
flation, or excessive loading, either sepa-
rately or in combination, can cause heat
buildup and tire failure.