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Wh eels and tire s – BMW 550i Sedan 2008 User Manual

Page 228

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Wh

eels

and

tire

s

226

Tire age

The manufacturing date of tires is contained in
the tire coding: DOT ... 3307 indicates that the
tire was manufactured in week 33 of 2007.
BMW recommends that you replace all tires
after 6 years at most, even if some tires may last
for 10 years.

Uniform Tire Quality Grading

Quality grades can be found where applicable
on the tire sidewall between tread shoulder and
maximum section width. For example:
Tread wear 200 Traction AA
Temperature A

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.
These grades represent the tire's ability to stop
on wet pavement, as measured under con-
trolled 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 straight-ahead braking traction

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

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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.

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RSC – run-flat tires

You will recognize run-flat tires by a circular
symbol containing the letters RSC on the side
of the tire, refer to page

227

.

M+S

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

XL

Indicates specially reinforced tires.

Online Edition for Part no. 01 41 0 014 240 - © 08/07 BMW AG

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