The Costco 5 Year Road Hazard Warranty will give you "replacement tires," but the fine print says they will give you a credit for purchase of new tires based on remaining tread wear. I discussed the "extra certificate warranty" with Discount Tires and they confirmed that as long as there is legal tread-wear left on the tire, they will actually replace it with a new tire. That is pretty significant, if you wind up having to use the warranty.