BMW 550i xDrive Sedan 2011 - Manual (Page 250)

DOT Quality Grades
Treadwear
Traction AA A B C
Temperature A B C
All passenger car tires must conform to Federal
Safety Requirements in addition to these
grades.
Treadwear
The treadwear grade is a comparative rating
based on the wear rate of the tire when tested
under controlled conditions on a specified gov‐
ernment test course. For example, a tire graded
150 would wear one and one-half, 1 g, 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 cli‐
mate.
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 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 252 , 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.
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Online Edition for Part no. 01 40 2 606 469 - 03 11 490
Wheels and tires