Does anyone know if Robart or another manufacturer make a solid tire replacement for the Robart 3-1/2" straight tread scale tire that comes on the 2-part plastic rim?
I know one option is to use the foam insert to stiffen it up, but was wondering if there was any solid options?

Don't know about a solid wheel replacement, but what about using that 'Great Stuff' Expanding Foam stuff inside the tire? I know the Blue Can of Great Stuff Expanding Foam is supposed to be flexable versus the Red Can Stuff.

Not sure if you already have the Foam Inserts, but if you decide to go that route, the foam inserts that Robarts sells are expensive and are made from 'Backer Cord', which you can get from Lowes or Home Depot, look in the Concrete/Masonary Section, you can get a Roll of the stuff and comes in different diameters, the larger diameter the stiffer you make the Tires/Wheels; its also found in the Storm Window/Door products section, where the weather Striping is located, there I think it's called Caulking Cord.

Don't ya just luv this forum!!

I was just contemplating this a day or two ago for my fat Zero which really flattens out the tires......Now I have an answer and a source without even having to ask

Thank you to you both! (query and reply)

could also use pipe insulation? - Cheap, fairly stiff....

I totally agree!