Tire tread – BMW 2012 X6M User Manual
Page 259
ernment test course. For example, a tire graded
150 would wear one and one-half (11/2) times
as well on the government course as a tire
graded 100. The relative performance of tires
depends upon the actual conditions of their use,
however, and may depart significantly from the
norm due to variations in driving habits, service
practices and differences in road characteristics
and climate.
Traction
The traction grades, from highest to lowest, are
AA, A, B, and C.
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 B and 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.◀
RSC – Run-flat tires
The symbol identifying run-flat tires is a circle
with the letters RSC on the sidewall, refer to
page
.
M+S
Winter and all-season tires.
These have better winter properties than
summer tires.
XL
Designation for specially reinforced 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.
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