A treadwear rating generally falls between 60 and 540. Treadwear ratings are determined by testing tires in a controlled environment to determine how long a tire's tread will last. After a 7,200 mile wear test, a treadwear rating is assigned.
Because treadwear ratings are assigned by tire manufacturers, comparisons are most effective between a specific manufacturer's products rather than across brands. A tire with a treadwear rating of 400, for example, is likely to last twice as long as a tire rated at 200.
The Uniform Tire Quality Grading System, or UTQGS, requires tire manufacturers to disclose treadwear, traction, and temperature information for tires they produce. This is designed to help customers decide which tires are most suitable to their needs.