Us Department Of Transportation - Aston Martin DB 9 2013 Manual

US Department of Transportation

Uniform Tire Quality Grades
The following information relates to the tire grading system
developed by the National Highway Traffic Safety Administration,
which grades tires by tread wear, traction and temperature
performance. All passenger vehicle tires must conform to federal
safety requirements in addition to these grades.
Tread Wear
The tread wear grade is a comparative rating based on the wear rate
of a tire tested, under controlled conditions, on a specified
government test course. For example, a tire graded 150 would wear
one and a half times (1½) 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 normal due to variations in driving habits, service practices
and differences in road characteristics and climate.
11.14
Traction
Warning: The traction grade assigned to this tire is based on
straight-ahead braking traction tests and does not include
acceleration, cornering, hydroplaning, or peak traction
characteristics.
The traction grades, from highest to lowest, are AA, A, B, and C. The
grades 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.
Temperature
Warning: The temperature grade for this tire is established
for a tire that is correctly inflated and not overloaded. Excessive
speed, under inflation, or excessive loading, either separately or
in combination, can cause heat buildup and possible tire failure.
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 temperature 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 vehicle tires must meet under the
Federal Motor Safety Standard No. 109. Grades B and A represent
higher levels of performance on the laboratory test wheel than the
minimum required by law.