Tire replacement – BMW 01 41 0 155 307 User Manual

Page 125

125

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Overview

To maintain good handling and vehicle
response, use only tires of a single
tread configuration from a single manu-
facturer. BMW tests and approves
wheel/tire combinations. Refer to
page

129

DOT Quality Grades

Treadwear
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 condi-
tions on a specified government test
course.

For example, a tire graded 150 would
wear one and one-half (1g) times as
well on the government course as a tire
graded 100. The relative performance
of tires depends upon the actual condi-
tions of their use, however, and may
depart significantly from the norm due
to variations in driving habits, service
practices and differences in road char-
acteristics 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 speci-
fied 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 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 condi-
tions 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 Stan-
dard No. 109. Grades B and A repre-
sent 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, under-inflation, or
excessive loading, either separately or
in combination, can cause heat buildup
and possible tire failure.

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

Do not use retreaded tires. Driving
safety may be impaired by their

use. This is due to the possible varia-
tions in casing structures and, in some
cases, to their extreme age, which can
lead to a decrease in their durability.

Tire replacement