The tire traction grade is one measure of Uniform Tire Quality Grading (UTQG) developed by the US Department of Transportation (DOT).
Measure: coefficient of friction on a water roadway under standardized conditions
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Asphalt g Force
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Concrete g Force
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Grade
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> 0.54
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> 0.38
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AA
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0.48 to 0.54 (> 0.47)
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0.36 to 0.38 (> 0.35)
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A
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0.39 to 0.47 (> 0.38)
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0.27 to 0.35 (> 0.26)
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B
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<= 0.38
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<= 0.26
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C
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If either surface is Grade C, then the tire is Grade C.
For Grades AA, A and B both criteria must be met.
The higher the grade the better the tire's traction and better the ability to stop on wet pavement.
There are other factors that impact stopping distance under different conditions3in addition to the tire traction grade.
