Uniform
Tire
Quality
Grading
The following information relates to the system
developed
by
the
United States National Highway
Traffic Safety Administration, which grades tires by
treadwear, traction and temperature performance.
(This
applies only to vehicles sold in the United States.) The
grades are molded on the sidewalls
of
most passenger
car tires. The Uniform Tire Quality Grading system
does not apply to deep tread, winter-type snow tires,
space-saver or temporary
use
spare tires,
tires
with
nominal
rim
diameters
of
10
to 12 inches
(25
to
30
cm),
or
to
some limited-production tires.
While the tires available on General Motors passenger
cars and light trucks may
vary
with respect to these
grades,
they
must also conform
to
Federal safety
requirements and additional General Motors Tire
Performance Criteria (TPC) standards.
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
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.
%action
--
A,
B,
C
The traction grades,
from
highest to lowest,
are
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.
Warning: The traction grade assigned to this tire is
based on braking (straight ahead) traction tests and
does not include cornering (turning) traction.
6-50
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