Buick 1993 LeSabre Owner's Manual page 261

A
CAUTION:
;
Mixing tires could cause you to lose control
while driving. If you mix tires of different sizes
or
types (radial and bias-belted tires), the vehicle
may not handle properly, and you could have a
crash. Be sure to use the same size and type
tires on all four wheels.
It's all right to drive with your compact spare,
though. It was developed for use on your vehicle.
I
I
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.)
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.
Traction
-
A, B, C
The traction grades, from highest to lowest are: A, B,
and C. 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.
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