Just wondering because ive seen pictures of the wheels and they look pretty small. And im guessing that they dont require air. Right now i have a 2 wheel "Ebay Special 100XT" and it works great for my belt wb. But i getting a 48' wb/hydro and i understand that the bull rider type is the only way to go with a hydro. So is it a smooth ride, or do your knees break at the end of the day?