Us Department Of Transportation - Aston Martin DB 9 2010 Manual

Tread Wear Marks
A
Tread wear marks (A) are incorporated
into the construction of all tires. These
marks are integral moulded ribs spaced
at regular intervals around the
circumference of the tire and extend
across the full width of the tread, in all
primary grooves.
When a tire has worn causing one or more of the marks to be flush
with the outer face of the tread the tire has reached its wear limit. It
then becomes illegal in certain countries and must be replaced.
11.16

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.
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.