BMW Z4 Roadster 2.5i 2004 - Manual (Page 80)

Wheels and tires
78
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 con-
trolled conditions on a specified indoor lab-
oratory 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.
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RSC: Run Flat tires
Run Flat tires are labeled on the sidewall
with a circular symbol containing the letters
RSC. Refer to page
80 .
M+S
Winter and all-season tires.
These have better winter performance
properties than summer 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.
Tire tread
Tread depth should not be allowed to go
below 1/8 in/3 mm even though in Europe,
for example, the legally specified minimum
tread depth is only 1/16 in/1.6 mm. Below
1/8 in/3 mm tread depth, there is a very
high risk of hydroplaning, even at relatively
moderate speeds and with only small
amounts of water on the road.
At tread depths below approx. 1/6 in/
4 mm, winter tires display a perceptible
decrease in their ability to cope with winter
driving conditions, and should be replaced
in the interest of safety.
Tread wear indicators in the tread-groove
base, see arrow, are distributed around the
wheel circumference and are labeled on
the tire sidewall as TWI, Tread Wear Indica-
tor. At a tread depth of 1/16 in/1.6 mm, the
indicators signal that the legally permissi-
ble wear limit has been reached.
Tire damage
Unusual vibrations encountered dur-
ing normal vehicle operation can indi-
cate tire failure or some other vehicle mal-
function. This type of problem can be
caused by contact with curbs, etc. This is
also true for irregularities in the vehicle's
handling characteristics, such as a pro-
nounced tendency to pull to the left or right.
Should this occur, respond by immediately
reducing your speed. Proceed carefully to
the nearest BMW center or professional tire
center, or have the vehicle towed there to
have it and its wheels or tires inspected.
Tire damage up to and including sudden
and complete air loss can pose an extreme
hazard for both vehicle occupants and
other road users.
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