Porsche Boxster Owner's Manual page 226

and a 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 conditions of their use, however, and
may depart significantly from the norm due to var-
iations in driving habits, service practices and dif-
ferences in road characteristics and climate.
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
224
Practical Tips, Emergency Service
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, result-
ing in serious personal injury or death.
Tire pressures
Warning!
Incorrect tire pressure causes increased tire
wear and adversely affects road handling.
This could lead to tire failure, resulting in loss
of control, leading to serious personal injury
or death.
f Always use an accurate tire pressure gage
when checking inflation pressures.
f Do not exceed the maximum tire pressure list-
ed on the tire sidewall.
Please see the chapter "TIRE PRESSURE PLA-
TE" on Page 275.
f Cold tire inflation pressure means: all tires
must be cold, ambient temperature maximum
(68 °F/20 °C) , when adjusting the inflation
pressure.
Avoid sunlight striking the tires before measur-
ing cold pressures, since the pressures would
rise from temperature influence.
f Valve caps protect the valve from dust and dirt,
and thus from leakage.
Always screw caps tightly down.
Replace missing caps immediately.
f Use only plastic valve caps.
f Do not use commercially available sealant or
tire inflating bottles. Only use Porsche
approved tire sealant.
f Please see the chapter "TIRE PRESSURE FOR
COLD TIRES (68 °F/20 °C)" on Page 277.