BMW 745I - Manual (Page 189)

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187
wear one and one-half – 1 g – 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 signifi-
cantly from the norm due to variations in
driving habits, service practices and differ-
ences 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
braking traction tests, and does not include
acceleration, cornering, hydroplaning, or
peak traction characteristics.
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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, underinflation, or excessive
loading, either separately or in combina-
tion, can cause heat buildup and possible
tire failure.
<
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:
Treadwear 200 Traction AA
Temperature A
Do not use retreaded tires, since dri-
ving safety may be impaired. Possible
variations in the design and the age – which
could be substantial – of the carcasses can
lead to unusually rapid wear.
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Tire age
The tire's date of manufacture is indicated
on the sidewall:
DOT ... 3402 indicates that a tire was
manufactured in week 34 of the year 2002.
Regardless of mileage or wear, BMW
recommends that you replace all tires –
including the spare – after a maximum of
6 years, even though the tires may have a
theoretical service life of up to 10 years.
Wheel and tire
combinations
The right choice
Use only wheel and tire combinations
that BMW has approved for your par-
ticular vehicle. Variations in factors such as
manufacturing tolerances mean that even
wheels and tires with identical official size
ratings could actually have different dimen-
sions than the approved units – these diffe-
rences 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 there-
fore cannot be held liable for driving
safety.
<
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.
Online Edition for Part No. 01 41 0 157 197 - © 11/02 BMW AG