Uniform Tire Quality Grading- Page 622

621

uu

Checking and Maintaining Tires

u

DOT Tire Quality Grading (U.S. Vehicles)

Main

tenan

ce

The traction grades, from highest to lowest, are AA, A, B, and C. 
Those grades 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 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.

■

Traction

■

Temperature

1

Traction

Warning: The traction grade 
assigned to this tire is based on 
straight-ahead braking traction tests, 
and does not include acceleration, 
cornering, hydroplaning, or peak 
traction characteristics.

1

Temperature

Warning: The temperature grade for 
this tire is established for a tire that is 
properly inflated and not 
overloaded. Excessive speed, 
underinflation, or excessive loading, 
either separately or in combination, 
can cause heat buildup and possible 
tire failure.