BMW x5 2000 Manual Do Utilizador

128

Tire replacement

To maintain good handling and vehicle
response, use only tires of a single
tread configuration from a single manu-
facturer. BMW tests and approves
wheel/tire combinations. Refer to
page

130

DOT Quality Grades

Treadwear
Traction AA A B C
Temperature A B C

All passenger car tires must con-
form to Federal Safety Require-

ments 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 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, hy-
droplaning, or peak traction character-
istics.

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 material of the tire to degenerate
and reduce tire life, and excessive tem-
perature 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 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 ex-
cessive loading, either separately or in
combination, can cause heat buildup
and possible tire failure.

Uniform Tire Quality Grading

Quality grades can be found where ap-
plicable on the tire sidewall between
tread shoulder and maximum section
width. For example:

Treadwear 200 Traction AA
Temperature A

Do not use retreaded tires, since
driving safety may be impaired by

their use. This is due to the possible
variations in casing structures and, in
some cases, to their extreme age,
which can lead to a decrease in their
durability.