Geo 1995 Prizm Owner's Manual page 235

Buying New Tires
To find out what kind and size of tires you need, look at
the Tire-Loading Information label.
Make sure the replacements are the same size, load
range, speed rating, and construction type (bias,
bias-belted or radial) as your original tires.
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.
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