Chevrolet 1993 Corvette Owner's Manual page 286

L
Unijiim Tire Quality
Grading
The
following information relates to the
system developed by the United States
National Highway Tr&c 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
wh<n tested under mntmlled conditions
on a specified government test course.
For example, a tire graded 150 would
wear one and
a
half (1%) times as well
on the govement course as a tire
graded 100. Therelative 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.