Uniform Tire Quality Grading - Lotus Evora 2011 Owner's Handbook Manual

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Uniform Tire Quality Grading

The following information relates to the system developed by
the United States National Highway Traffic Safety Administra
tion, which grades tires by treadwear, traction and temperature
performance. The grades are moulded on the sidewalls of most
passenger car tires between the tread shoulder and maximum
section width. For example:
Treadwear 180 Traction AA Temperature A
Treadwear
The treadwear grade is a comparative rating based on the
wear rate of the tire when tested under controlled conditions on
a specified government test course. For example, a tire graded
150 would wear one and a half (1.5) times as well on the govern-
ment course as a tire graded 100. The relative performance of
tires depends, however, upon the actual conditions of their use,
and may differ significantly from the norm due to variations in
driving habits, service practices, and differences in road char
acteristics and climates.
Traction - AA, A, B, C: The traction grades, from highest to low
est are: AA, A, B, and C. They represent the tire's grip 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 is based on braking (straight ahead) tests
and does not include acceleration, cornering, 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 speed cruising, or a demanding driving style can generate
high tire temperatures which can cause the material of the tire
to degenerate and reduce tire life. Excessive temperature can
also result in sudden tire failure. Temperature grade 'C' is a
level of performance which all passenger car tires must meet.
Grades 'B' and 'A' represent higher levels of performance on the
laboratory test wheel than the minimum required by law.
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