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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,
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
controlled conditions on specified govern-
ment 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 brak-
ing 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 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 load-
ing, either separately or in combination,
can cause heat buildup and possible tire
failure.<
74
Online Edition for Part-No. 01 41 0 156 897 - © 09/02 BMW AG
Uniform Tire Quality Grading
Quality grades can be found where appli-
cable on the tire sidewall between tread
shoulder and maximum section width. For
example:
Tread wear 200 Traction AA
Temperature A
Wheel and tire combina-
tions
The right choice
Use wheels and tires approved by
BMW for your particular vehicle. Vari-
ations in factors such as manufacturing tol-
erances mean that even wheels and tires
with identical official size ratings could
actually have dimensions different from the
approved units. These differences could
lead to body contact, and with it the risk of
severe accidents. If non-approved wheels
and tires are used, BMW cannot evaluate
their suitability, and therefore cannot be
held liable for driving
BMW tests certain tire brands for each tire
size, classifies them as road-safe and
approves them. Consult your BMW center
for more information. Observe any country-
specific regulations, e.g. on making a cor-
responding entry in the vehicle documents.
The correct wheel and tire combina-
tion affects different systems such as
ABS, DSC, DTC and DBC. The function of
these systems is impaired if improper
wheel and tire combinations are used.
For this reason, use tires of the same brand
and tread configuration. In the event of a
flat tire, for example, remount the approved
wheel and tire combination as soon as pos-
sible.<
safety.<
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