Porsche cayman gt4 Owner's Manual page 189

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Tire damage while
DANGER
driving
Driving with damaged tires could cause you to
lose control of the vehicle.
f
If while driving, your vehicle experiences a
sudden vibration or ride disturbance, and/or
you suspect that possible damage to your tires
or vehicle has occurred, you should
immediately reduce your speed without
excessive use of the brakes.
f
Stop the vehicle as soon as possible, and
inspect the tires.
If you cannot determine the cause for the
disturbance, have your vehicle towed to the
nearest Porsche or tire dealer to have your
vehicle or tire(s) inspected.
f
Continuing to operate the vehicle without
correction could result in a loss of control.
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.
Treadwear
The treadwear grade is a comparative rating
based on the wear rate of the tire when tested
under controlled conditions on a specific
government 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 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 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
controlled conditions on specified government
test surfaces of asphalt and concrete. A tire
marked C may have poor traction performance.
Information
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
generation 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.
Minor Repairs
187