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Wheels and tires MOBILITY
207
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
government test course. For example, a tire
graded 150 would wear one and one-half (1γ)
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 may depart significantly from the
norm due to variations in driving habits, service
practices and differences in road characteristics
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 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,
cornering, hydroplaning, or peak traction
characteristics.<
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 Vehicle
Safety Standard No. 109. Grades B and A repre-
sent levels of performance on the laboratory test
wheel that exceed 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
separately or in combination, can cause heat
buildup and possible tire failure.<
RSC - run-flat tires
You will recognize run-flat tires by a circular
symbol containing the letters RSC on the side of
the tire, page 208.
M+S
Winter and all-season tires.
These have better winter properties than
summer tires.
XL
Designation for specially reinforced tires.
Tire condition
Inspect your tires regularly for tread wear, signs
of damage and for foreign objects lodged in the
tread. Check the tread depth.
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.
Online Edition for Part no. 01 40 2 914 807 - © 07/12 BMW AG
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