As I said in a previous post on this thread, refering back to the (brief) time when we towed our Kia Sedona minivan on a dolly:
The only tow dolly I ever found that works good with minivans, is the Acme EZE tow dolly.
Just about every other dolly we looked at would not work either due to weight limitations, or concerns over fender contact when turning.
Contrary to what a previous poster suggested, yes, you DO have to account for the entire weight of the towed vehicle. If a dolly says it is rated to handle only a 4,000 lb vehicle, then it is not a good idea to tow a 4500 lb van with it. Not only that, but you have to consider the weight limitation of the Motorhome's hitch receiver. Many are limited to 5,000 lbs, and this means the weight of the vehilce PLUS the dolly needs to be under that 5,000 lbs. When most vans weigh 4500 lbs or more, this rules out many dollies as their weight + 4500 would put you over the 5000 limit. The Acme dolly with its light 400 lb total weight and 5000 lb vehicle rating makes it ideal for minivans.
As far as width, turning goes: Based on what some tow dolly manufacturers would recommend, it seems they expect you to just avoid any turns more than 45 degrees, haha. :)
Pivot tables just do not allow for much pivoting/turning with wider vehicles like vans. There are a few dollies that the wheels on the dolly itself are steerable. This is much better, but problem is those dollies tend to be so heavy, the 5,000 lb limit of the hitch receiver becomes an issue.
Acme EZE dolly takes a whole different approach that seems to work best and allow for the tightest turning: They use a solid, non-pivoting platform that the vehicle sits on, and instruct you to leave steering wheel unlocked to allow for pivoting. They use small enough wheels, fenders, that contact is just about impossible no matter how tight you turn. Check out the videos of this dolly on their web page, you'll see what I mean. Its almost as if the fenders, wheels of the dolly become one with the front wheels of the towed vehicle. I actually tested this with our van, MH in a parking lot once. I could literally turn so tight that front of van was about to make contact with the back of the MH (easily 90 degree angle between the two, and there was no contact with fenders of the van.
If we were ever to go back to using a dolly to tow, no question, it will be with an Acme EZE dolly.