Uniform Tire Quality Grading - GMC 1999 Savana Van Owner's Manual

CAUTION:
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If you use bias ply tires on your vehicle, the
wheel rim flanges could develop cracks after
many miles of driving. A tire and/or wheel could
fail suddenly, causing a crash. Use only radial
tires with the wheels on your vehicle.

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
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tires, space saver or temporary use spare tires, tires with
nominal rim diameters of 10 to 12 inches (25 to 30 cm),
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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
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ply
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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