Porsche 911 Carrera Manual page 187

Traction AA, A, B, C
The traction grades, from highest to lowest, are
AA, A, B, and C and they represent the tire's ability
to stop on wet pavement as measured under con-
trolled conditions on specified government test
surfaces of asphalt and concrete.
A tire marked C may have poor traction perform-
ance.
Warning!
The traction grade assigned to this is based on
braking (straight-ahead) traction tests and does
not include cornering (turned) traction, accelera-
tion, hydroplaning or peak traction characteris-
tics.
Temperature A, B, C
The temperature grades are A (the highest), B and
C, representing the tire's resistance to the gener-
ation of heat and its ability to dissipate heat when
tested under controlled conditions on a specified
indoor laboratory test wheel.
Sustained high temperatures can cause the mate-
rial 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 perform-
ance which all passenger car tires must meet un-
der the Federal Motor Vehicle Safety Standard No.
109.
Grades B and A represent higher levels of per-
formance 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 overload-
ed.
Excessive speed, underinflation, or excessive
loading, either separately or in combination, can
cause heat buildup and possible tire failure.
187
Practical Tips, Emergency Service