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Tire replacement
To maintain good handling and vehicle
response, use only tires of a single tread
configuration from a single manufac-
turer. BMW tests and approves wheel/
tire combinations. Refer to page 122.
DOT Quality Grades
Treadwear
Traction AA A B C
Temperature A B C
All passenger car tires must con-
form to Federal Safety Require-
ments in addition to these grades.<
Treadwear
The treadwear 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 (1 1/2) 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 as-
phalt 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, hydro-
planing, or peak traction characteris-
tics.<
Temperature
The temperature grades are A (the high-
est), B and C, representing the tire’s re-
sistance to the generation of heat and
its ability to dissipate heat when tested
under controlled conditions on a speci-
fied indoor laboratory test wheel.
Sustained high temperature can cause
the material of the tire to degenerate
and reduce tire life, and excessive tem-
perature can lead to sudden tire failure.
The grade C correspods to a level of
performance which all passenger car
tires must meet under the Federal Mo-
tor Vehicle 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 ex-
cessive 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:
Treadwear 200 Traction AA
Temperature A
Online Edition Part-No. 01 41 0 155 062 - © 07/99 BMW AG