Tire tread, Tire damage – BMW 550i xDrive Gran Turismo 2011 User Manual

Page 247

Those grades represent the tire's ability to stop
on wet pavement as measured under controlled
conditions on specified government test surfa‐
ces 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, hydro‐
planing, or peak traction characteristics.

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. Sus‐
tained 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 Band A represent
higher levels of performance on the laboratory
test wheel than the minimum required by law.

Temperature grade for this tire
The temperature grade for this tire is es‐

tablished for a tire that is properly inflated and
not overloaded. Excessive speed, underinfla‐
tion, or excessive loading, either separately or in
combination, can cause heat buildup and pos‐
sible tire failure.
If necessary, have the vehicle towed.◀

RSC – Run-flat tires

Run-flat tires, refer to page

249

, are labeled with

a circular symbol containing the letters RSC
marked on the sidewall.

M+S

Winter and all-season tires with better cold
weather performance than summer tires.

Tire tread

Summer tires

Do not drive with a tire tread depth of less than
0.12 in/3 mm.
There is an increased danger of hydroplaning if
the tread depth is less than 0.12 in/3 mm.

Winter tires

Do not drive with a tire tread depth of less than
0.16 in/4 mm.
Below a tread depth of 0.16 in/4 mm, tires are
less suitable for winter operation.

Minimum tread depth

Wear indicators are distributed around the tire's
circumference and have the legally required
minimum height of 0.063 in/1.6 mm.

They are marked on the side of the tire with TWI,
Tread Wear Indicator.

Tire damage

General information

Inspect your tires often for damage, foreign ob‐
jects lodged in the tread, and tread wear.

Notes

Indications of tire damage or other vehicle de‐
fects:

▷

Unusual vibrations during driving.