Let me share an experience from today (04/23/18); brought my car in to have a tire patched (slow leak). 3-4 hr wait. Was told that Firestone only covered 12,000 mi or 12 mos on tire warranties from Fletcher's which Firestone obtained apprx 2 yrs ago. Tires are still inside 40k mi warranty, but outside the 12 mo time/12K mi window's. Finally, the service advisor got off his duff and went outside to check the tire. When he came back, I was told "I can't patch that tire because it has a wear ring that indicates possible internal damage to the blackwall" Me: "A what? So I have to drive with a slow leaking tire?" He: "I can fill with air" The SA gave me a quote for 168.33 for replacement tire. Frustrated, I left. On a whim, I wound up at Discount Tire about a mile closer to home. The store Manager Chris walked me out to inspect the tire and found a torn/chafed valve stem. He checked the other 3 and they were in the same condition. I walked out of the store about 1.5 hrs later with 4 new valve stems + tire balance for 20.00 At no time did a Discount Tire service tech inform me of any "damage ring".
I suppose it's possible if the rim rides on the tire long enough to cause outside blackwall damage. But geezus......
If don't mind wasting your hard earned cash on goods or services you don't need, then by all means, visit this Firestone Complete Auto Rip-off, I mean Care.
Otherwise, visit Discount Tire. My NEW tire place. Discount Tire is more interested in making a new customer into an old customer.