"My Michelin Defender tires have a 50,000 mile treadwear warranty and I've got 85,000 miles on them! They're gggggreeat!", says Tony 'The Touring' Tiger.
Most of Michelin's competitors use the industry standard for light truck tires or 50,000 mile warranty, so Michelin started doing the same thing. And for the very reason illustrated in the "quote" above.
Mileage rating numbers aren't even an indication, much less a promise, of how many miles a tire will or should get. It's all marketing. There is an actual treadwear rating stamped (or molded, I guess it's more accurate) on the side of the tire, but that's just a relative thing. A rating of 300 means the tire will have 3x the treadwear longevity of a tire with a 100 rating. And even those ratings come from the manufacturer and not the government or some independent testing agency.
If the tread wears out prematurely, meaning 2/32 or less, like at 30,000 miles, the best you can hope for is a prorated reimbursement, and even that's iffy. In most cases all 4 tires need to have the same exact treadwear, otherwise you've got something wrong with your vehicle that's causing the odd wear on just one or two tires. In other cases you have to have receipts showing the tires have been rotated according to manufacturer recommendations (like every 5000 miles or something). In all cases, the amount of the prorated amount is against the manufacturer's suggested retail price or a dealer's price, which is usually higher than a retailer's price, meaning it's often cheaper to just buy a new tire discounted from a retailer than it is to warranty replace it. (now, that's just for treadwear, not for some creepy balloon buldge on the sidewall or some other manufacturer defect)
Consumer Reports is constantly testing tires for treadwear, and their reports show that other than one or two tire brands you've probably never heard of, like the Nokian Entire (80,000 mile warranty but wore out at 35,000 miles), most will be within 15,000 miles of the stated warranty mileage.
The Continental TrueContact and PureContact (H, V), Sumitomo HTR Enhance L/X (T, H, V), Kumho Solus TA71 and TA11, Firestone Precision Touring, and Bridgestone Serenity Plus tires all fell short of their stated numbers, but were well within that 15,000 miles, so close enough.
The longest lasting was the Pirelli P4 Four Seasons Plus, which lasted 100,000 miles. A close second was the Michelin Defender, and numbers 3 and 4 on that list were also Michelin tires.
My current M/S2 tires have 122,000 miles on them and they have a really long way to go yet. My previous set was so far above 200,000 that I don't even want to post the number. It was ridiculous. Even the guys at Discount Tire were giddy about it, because the numbers were right there in their computer. I attribute the lengthy wear on quick and regular replacement of ball joints and wheel bearings, (rotations were only done every 50,000 miles ballpark) and to nitrogen.
