BMW 645Ci Coupe 2005 - Manual (Page 172)

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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 Vehi-
cle 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 excessive loading, either sep-
arately or in combination, can cause heat
buildup and possible tire failure.
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RSC – run-flat tires
You will recognize run-flat tires by a circular
symbol containing the letters RSC on the side
of the tire, refer to page
172 .
M+S
Winter and all-season tires.
These have better winter properties than sum-
mer tires.
Tire condition
Inspect your tires frequently for tread wear,
signs of damage and foreign objects lodged in
the tread, and check the tread depth.
Minimum tread depth
The tread depth should not drop below 0.12 in/
3 mm, although, for example, European legisla-
tion only specifies a minimum tread depth of
0.063 in/1.6 mm.
At tread depths below 0.12 in/3 mm there is an
increased risk of high-speed hydroplaning,
even when only small amounts of water are
present on the road surface.
Winter tires noticeably loose their suitability for
winter use below a tread depth of 0.16 in/4 mm.
New tires should be mounted in the interest of
safety.
Wear indicators at the tread-groove base, refer
to arrow, are distributed over the tire's circum-
ference and are marked on the side of the tire
with TWI – Tread Wear Indicator. If the indica-
tors are at the level of the profile, the legal per-
missible tread depth of 0.063 in/1.6 mm has
been reached.
Tire damage
Due to low-profile tires, please note that
wheels, tires and suspension parts are
more susceptible to road hazard and conse-
quential damages.
Unusual vibrations encountered during normal
vehicle operation can indicate tire failure or
some other vehicle defect. This can, for exam-
ple, be caused by driving over curbs. These
kinds of problems may also be signaled by other
changes in vehicle response, such as a strong
tendency to pull to the left or right.
In these cases reduce your speed immediately
and have the wheels and tires inspected imme-
diately. To do this, carefully drive to the next
BMW center or a specialized tire dealer which
works with personnel trained in accordance
with BMW specifications. Have the vehicle
towed to the workshop if necessary.
Tire damage can be extremely dangerous to
vehicle occupants and other road users.
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Unprofessional attempts by laymen to
service tires can lead to damage and acci-
dents. Have this work performed by skilled pro-
fessionals only. The technicians at your BMW
center will be glad to assist you with the
required professional knowledge and special-
ized equipment.
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