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.