Tire coding – BMW Z4 Roadster 2.5i 2004 User Manual
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Tire coding
Understanding the lettering on the tire
sidewall makes it easier to identify and
choose the correct tires.
Tire size
e.g.
225/50 R 16 92 V
Nominal width in mm
Cross-sectional
ratio in %
Radial belt construction
Rim diameter in inches
Load index,
not on ZR tires
Speed code letter,
in front of the R on ZR tires
Speed code letters
Q = up to 105 mph / 160 km/h
T
= up to 118 mph / 190 km/h
H = up to 131 mph / 210 km/h
V
= up to 150 mph / 240 km/h
W = up to 167 mph / 270 km/h
Y
= up to 186 mph / 300 km/h
Tire Identification Number
Tires with DOT codes meet the guidelines
of the U.S. Department of Transportation.
DOT code:
e.g.
DOT xxxx xxx 3603
Manufacturer's code
for tire brand
Tire size and
tire version
Tire age
Tire age
The date on which the tire was manufac-
tured is indicated by the code on the side-
wall:
DOT … 3603 indicates that the tire was
manufactured in week 36 of the year 2003.
BMW recommends the replacement of all
tires every 6 years at the latest, even if a tire
usage of 10 years is possible.
Uniform Tire Quality Grading
Quality grades can be found where appli-
cable on the tire sidewall between tread
shoulder and maximum section width. For
example:
Treadwear 200 Traction AA
Temperature A
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.
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Tread wear
The tread wear grade is a comparative rat-
ing based on the wear rate of the tire when
tested under controlled conditions on a
specified government test course.
For example, a tire graded 150 would wear
one and one-half, 1 1/2, 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 govern-
ment test surfaces 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 brak-
ing traction tests, and does not include
acceleration, cornering, hydroplaning, or
peak traction characteristics.
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