Volvo 2009 C70 User Manual download pdf (Page 179)

07 Wheels and tires

Uniform tire quality gradings

07

179

Uniform tire quality gradings

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 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 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 corre-

sponds 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 per-

formance 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.

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