Some passenger tires are covered by a manufacturer's limited warranty for treadwear. No tire manufacturer can guarantee you a certain number of miles from a given tire. Driving habits, driving conditions, road conditions, and vehicle maintenance all play a part in the tread life of a tire.
If a tire does not reach the warranted mileage, and the owner of the tire(s) has complied with the terms and conditions of the warranty, the manufacturer will replace the tire(s) as follows.
If, as indicated by your new tire invoice, your tires wear evenly across the tread, down to the treadwear indicators (2/32nds of an inch (1.6mm) of tread remaining) before providing the warranted miles of service as indicated by the properly functioning vehicle odometer, they will be replaced with comparable new passenger tires for a pro rata charge based on mileage received. The mileage received will be based on the current vehicle mileage on the odometer compared to the vehicle mileage at the time of new tire installation, which must be listed on the new tire invoice and the original owner of the tire's installation information record.
If the mileage warranty says NA, the tire manufacturer has not put a mileage warranty on the tire.