BMW Z8 2000, Owner'S Manual

Page: 99 / 172

98 n
Tire replacement
To maintain good handling and vehicle
response, use only tires of a single tread
configuration from a single manufac-
turer. BMW tests and approves wheel/
tire combinations. Refer to page
103 .
DOT Quality Grades
Tread wear
Traction AA A B C
Temperature A B C
All passenger vehicle 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
rating based on the wear rate of the tire
when tested under controlled condi-
tions 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 condi-
tions of their use, however, and may
depart significantly from the norm due
to variations in driving habits, service
practices and differences in road char-
acteristics 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 speci-
fied government test surfaces of as-
phalt 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,
hydroplaning, or peak traction charac-
teristics.
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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 condi-
tions on a specified indoor laboratory
test wheel.
Sustained high temperature can cause
the tire material to degenerate and re-
duce tire life, and excessive tempera-
ture can lead to sudden tire failure. The
Grade C corresponds to a level of per-
formance which all passenger vehicle
tires must meet under the Federal Mo-
tor 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.
The temperature grade for this
tire is established for a tire that is
properly inflated and not overloaded.
Excessive speed, underinflation, or
excessive loading, either separately or
in combination, can cause heat buildup
and possible tire failure.
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