IMO, if you get any adjustment from Firestone, it would have to be just because the rep bent over backwards and went above and beyond. Reason being, you can't verify how the tractor and tires were used. They might have been run at extremely low PSI under very heavy loads with lots of slippage. Or abused in some other way. Not siding with Firestone at all, I hope you get some help on them. Also, you didn't mention how many hours on the tractor, that would surely have some bearing on their decision, too, I would think.