Mine came with 15's and I put Goodyear Endurance in 235/80/16 as they are a little shorter and wider than the 235/85's. You can look up the exact specs. I didn't want to deal with tire clearance issues as it was a pretty big jump over the stock 15's. No clearance problems whatsover. Just make sure your springs are mounted on the lowest holes.
For comparison, here are the same 16's against the 15's on our previous FR Wildcat. The Goodyears and rims were new when I traded it for the Jayco, so they took them off the Wildcat and put them on the Jayco. From memory I gained about an inch and a half in height. Not nearly enough for it to sit level with my Ram, but the tires have a way more load rating than the originals, so I'm not too worried.