BMW X3 xDrive30i 2009 - Manual (Page 100)

Wheels and tires
98
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 that 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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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 for foreign objects lodged
in the tread. Check the tread depth.
Minimum tread depth
The tread depth should not fall below 0.12 in/
3 mm. At tread depths below 0.12 in/3 mm,
there is an increased risk of high-speed hydro-
planing, even when only small amounts of water
are present on the road surface.
Winter tires display a noticeable loss in their
ability to cope with cold-weather driving condi-
tions once the tread wears to below 0.16 in/
4 mm. To ensure continued safety you should
always have such tires replaced.
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 tire tread
has worn down to the wear indicators, then the
legally permissible tread depth limit of 0.063 in/
1.6 mm has been reached.
Wheel/tire damage
Please note that low-profile tires, make
wheels, tires and suspension parts more
susceptible to road hazard and consequential
damages.
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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. The same
applies to any other abnormal road behavior,
such as pulling severely to the right or left.
In these cases, reduce speed immedi-
ately and have wheels and tires checked
immediately. Drive carefully to the nearest
BMW Sports Activity Vehicle Center or tire spe-
cialist. Have the vehicle towed to one of these
locations if necessary.
Tire damage can pose a potentially lethal safety
hazard for the vehicle's occupants and other
road users alike.
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New wheels and tires
Have new wheels and tires installed only
by your BMW Sports Activity Vehicle
Center or a tire shop that works according to
BMW repair procedures with correspondingly
trained personnel. If this work is not carried out
properly, there is a danger of subsequent dam-
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