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135n
RepairsIndex OverviewControlsCar careTechnologyData
Tire replacement
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 137.
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 cha-
racteristics 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 characteri-
stics.<
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 tem-
perature 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 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 pro-
perly inflated and not overloaded. Ex-
cessive speed, underinflation, or exces-
sive loading, either separately or in
combination, can cause heat buildup
and possible tire failure.<
Online Edition for Part No. 01 41 0 155 012 - © 07/99 BMW AG
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