On Tuesday, October 6, 2020 at 11:07:02 PM UTC-4, George Haeh wrote:
Last year I replaced the 200 x 50 tube. A few days ago it was low and I pumped it up to 36 or so pounds according to max pressure on the tire.

The next day the tire came off the rim and won't stay on even with much reduced pressure. Can't really complain as could have been on for 20+ years.

In the interim I just bought a Princess Auto (Canuck for Harbor Freight) solid rubber wheel that I hope can be made to work with a few extra washers.

Does anybody know a decent supplier for dolly tires?

Check with W&W. They carry a replacement wheel for the IMI tail dollies, which were originally delivered with air-less solid foam tires. These tended to swell up and pop off the rim when used on hot black-top as found in Moriarty in June!
The replacement is an air tire 2.50-4, which they call 'Military Tread' and can be inflated to 50psi.
The hub is 75mm wide and the hole in the bearing is dia. 20mm. The dolly uses a bushing inside that bearing in order to bring the bolt size down.
Mine has not yet popped off the rim.

Uli
'AS'