Porsche Cayenne 2009 Owner's Manual page 284

Example
Uniform Tire Quality Grading
Quality grades can be found where applicable on
the tire sidewall between tread shoulder and
maximum section width.
All passenger car tires must conform to Federal
Safety Requirements in addition to these grades.
284
Minor Repairs
Treadwear
The treadwear grade is a comparative rating
based on the wear rate of the tire when tested
under controlled conditions on a specific govern-
ment test course. For example, a tire graded 150
would wear one 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 ac-
tual conditions of their use, however, and may de-
part significantly from the norm due to variations
in driving habits, service practices and differences
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 performance.
Warning!
The traction grade assigned to this is based
on braking (straight-ahead) traction tests
and does not include cornering (turned)
traction, acceleration, hydroplaning or peak
traction characteristics.
Temperature A, B, C
The temperature grades are A (the highest), B and
C, representing the tire's resistance to the genera-
tion 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
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 car 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 estab-
lished for a tire that is properly inflated and
not overloaded. Excessive speed, underinfla-
tion, or excessive loading, either separately
or in combination, can cause heat buildup
and possible tire failure, resulting loss of
control, leading to serious personal injury or
death.