Ford Mercury Villager 1997 Owner's Manual page 308

150 would wear one and one-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, and
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.
The traction grade assigned to this tire is based on
braking (straightahead) 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 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.
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