Hello,
I do not have a spare wheel, but I checked about the Seitech dolly wheel a few years ago ago when I thought my tire might have been ruined (but luckily it was not and it is still holding well), so let me share what I found at that time. I have been using Seitech dolly with "beach wheels”. (The photo attached. Emilio would find another duct tape in it….)
Basically there is no more Seitech, so we cannot get original Seitech dolly wheels any more. But the dollies from the Dynamic Dollies & Racks are compatible with Seitech’s, so we can get the "standard dolly wheel" from them.
But getting “beach dolly wheel” is difficult. Dynamic Dollies & Racks has the one, but this one looks huge.
So I was wondering how I could get the beach wheel that looks like the original Seitech’s. What I found was: the wheels for the Go-Kart or ATV might work. The following seems to have the same with and similar look:
These do not come with the rims, so we need to figure out how to attach the wheel to the rim, which we might be able to find in Youtube.
Luckily, I did not have to go this route, but if my dolly wheel went really bad, using these Go-Kart wheel might be something I would consider as an option.