Mercedes-Benz 2002 SLK 230 Kompressor Operator's Manual page 276

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
surfaces of asphalt and concrete. A tire marked "C" may
have poor traction performance.
Warning!
The traction grade assigned to this tire is based on
straightahead braking traction tests, and does not
include acceleration, cornering, hydroplaning, or
peak traction characteristics.
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Instruments
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273
Instrument
Driving
cluster display
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 sudden
tire failure. The grade "C" corresponds to a level of
performance which all passenger vehicle tires must
meet under the Federal Motor 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.
Warning!
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 excessive heat build up
and possible tire failure.
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