This thing is just a flat roller and it doesn't have any bearings in it. I figured I'd keep it simple, as anything with bearings would significantly add to the cost, and it was hard to find anything that could take the weight. In fact, I looked around, and couldn't, so I gave up on the swivel idea pretty quickly.
It doesn't spend a lot of time on the ground - only about 6-8 feet as I roll through that area, and if there is any sideways movement, which in my case there isn't, it can just scrap sideways a little.
If you're turning too much, enough to need a caster while your back end is hitting the ground, it might be wise to consider the logistics of putting the bus in that location in the first place. I only use this in this garage. If I'm out on the road, I don't even have the thing with me. g