Tire condition, Wh eels and tire s – BMW M5 Sedan 2007 User Manual

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eels

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tire

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DOT Quality Grades

Tread wear
Traction AA A B C
Temperature A B C

All passenger car tires must conform to
Federal Safety Requirements in addition

to these grades.

Tread wear

The tread wear 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 graded
150 would wear one and one-half (1

γ) 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, how-
ever, and may depart significantly from the
norm due to variations in driving habits, service
practices and differences in road characteris-
tics and climate.

Traction

The traction grades, from highest to lowest, are
AA, A, B, and C.
Those grades represent the tire's ability to stop
on wet pavement 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 traction grade assigned to this tire is
based on straight-ahead braking traction

tests, and does not include acceleration, cor-
nering, hydroplaning, or peak traction charac-
teristics.

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 level of performance which all passenger car

tires must meet under the Federal Motor Vehi-
cle Safety Standard No. 109. Grades B and A
represent higher levels of performance on the
laboratory test wheel than the minimum
required by law.

The temperature grade for this tire is
established for a tire that is properly

inflated and not overloaded. Excessive speed,
underinflation, or excessive loading, either sep-
arately or in combination, can cause heat
buildup and possible tire failure.

M+S

Winter and all-season tires.
These have better winter properties than sum-
mer tires.

Indicates specially reinforced tires.

Tire condition

Inspect your tires frequently for tread wear,
signs of damage and for foreign objects lodged
in the tread. Check the tread depth.

Minimum tread depth

The tread depth should not drop below 0.12 in/
3 mm, although, for example, European legisla-
tion only specifies a minimum tread depth of
0.063 in/1.6 mm. At tread depths below 0.12 in/
3 mm there is an increased risk of high-speed
hydroplaning, even when only small amounts of
water are present on the road surface.
When winter tires wear down past a tread depth
of 0.16 in/4 mm, they become perceptibly less
suitable for winter conditions. For the sake of
safety, new tires should be installed.

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