I think you could go up a size without any noticeable difference. I have a '21 Trail Boss. The factory tire size is the same as yours. Granted, the Trail Boss has a factory 2" lift, but I was able to go up to 295 70 18 Falken Wildpeaks with the stock suspension. My speedometer is 2 mph too slow with the new tires and gas mileage has remained the same.