Treadwear grade is a rating on the tire code that measures a tire's durability based on manufacturer tests. This rating is required by the U.S. Department of Transportation to determine how a quickly a tire wears compared to a standard reference tire, which is graded at 100. If a tire's treadwear rating is 300, that means it should last about three times as long as a standard tire with a 100 grade. In theory, the higher the grade, the longer the tread and actual tire should last.
Facts about treadwear grade