Tire condition, Replacing wheels/tires – BMW X3 3.0i SAV 2004 User Manual
Page 91
89
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 load-
ing, either separately or in combination,
can cause heat buildup and possible tire
failure.
<
M+S
Winter and all-season tires.
These have better winter properties than
summer tires.
Tire condition
Inspect your tires frequently for treadwear,
signs of damage and for foreign objects
lodged in the tread. Check the tread pat-
tern depth.
Tire tread
The tread depth should not drop below
0.12 in/3 mm, although, for example, Euro-
pean legislation 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.
As winter tires display a noticeable loss in
their ability to cope with cold-weather driv-
ing conditions 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
circumference and are marked on the tire
sidewall with TWI – Tread Wear Indicator.
At a tread depth of 0.063 in/1.6 mm these
indicators, signal that the tires have
reached the legally permissible wear limit.
Tire damage
Unusual vibrations encountered dur-
ing normal vehicle operation can indi-
cate tire failure or some other vehicle
defect. This can, for example, be caused by
driving over curbs. These kinds of prob-
lems may also be signaled by other
changes in vehicle response, such as a
strong tendency to pull to the left or right.
Should this occur, respond by immediately
reducing your speed. Proceed carefully to
the nearest BMW Sports Activity Vehicle
Center or professional tire center, or have
the vehicle towed in to have it, its wheels
and tires inspected.
Tire damage, extending to sudden and
complete loss of pressure in extreme
cases, can pose a potentially lethal safety
hazard for the vehicle's occupants and
other road users alike.
<
Replacing wheels/tires
Unprofessional attempts by laymen to
service tires can lead to damage and
accidents.
Have this work performed by skilled pro-
fessionals only. All BMW Sports Activity
Vehicle Centers will be happy to help you
Online Edition for Part No. 01 41 0 157 631 - © 07/03 BMW AG