Jaguar XK JJM 18 02 30 701 - Manual (Page 243)

277
Wheels and Tires
R
UNITED STATES 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 will grade tires by
tread wear, traction and temperature
performance.
Tread wear
The tread wear 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 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
The traction grades, from the highest to
the 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.
!
WARNING:
The traction grade assigned to this tire
is based on straight-ahead braking
traction tests and does not include
cornering (turning) traction 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 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 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.
!
WARNING:
The temperature grade for this tire is
established for a tire that is properly
inflated and not over loaded. Excessive
speed, under-inflation or excessive
loading, either separately or in
combination, can cause heat build-up
and possible tire failure.