Mini COOPER User Manual download pdf (Page 85)

83

OVERVIEWREPAIRS OPERATION CONTROLSDATAINDEX

TIRE REPLACEMENT

To maintain good handling and vehicle

response, use only tires of a single tread

configuration from a single manufacturer.

The manufacturer of your MINI tests and

approves wheel and tire combinations.

Do not use retreaded tires, since

driving safety may be impaired. 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.<

DOT Quality Grades

Tread wear

Traction AA A B C

Temperature A B C

All passenger car tires must conform

to Federal Safety Requirements in

addition to these grades.<

Tread wear

The tread wear grade is a comparative

rating 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 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 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

braking traction tests, and does not include

acceleration, cornering, hydroplaning, 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.

Sustained high temperature can cause the

material of the tire to degenerate and

reduce tire life, and excessive temperature

can lead to a sudden flat tire. The grade C

corresponds to a level of performance

which all passenger car tires must meet

under the Federal Motor Car Safety Stan-

dard No. 109. Grades B and A represent

higher levels of performance on the labora-

tory 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.<

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:

Tread wear 200

Traction AA

Temperature A

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