I use Michelin LTX M&S2 tires on our E450 Class C motorhome with their 70,000 mile tread warranty, in size 215/85R16 Load Range E.
Size 215/85R16 in Load Range E is rated for the identical weights at the indentical pressures on the same rims as the size 225/75R16 Load Range E that comes stock on most Ford chassis Class C motorhomes. However, I went with 215/85R16 because this tire size has a 1.2 inch larger diameter ... which gives me 0.6 inches higher ground clearance for less rear end dragging during offroad use, and when going into/out-of parking lots and shopping centers.