Have 14 Mega 3500 SRW running factory tires ( Firestone Transport 275/70r/18 About 26000 and down to less then half tread depth. about 18000 miles towing 6900lbs on rear axle when towing. Original depth 15/32 most tires showing between 6-7 32nds. I do rotate . Run 60 up front 80 in rear when loaded and 60 in rear when empty . Any one getting any better mileage when towing . Thinking of seeing a Firestone representive about rapid wear. :{:{