Take a look at the yahoo group. About 5 years ago there was
conversation about using a wheelchair innertube for the tailwheel. I
unfortunatly don't remember the exact size it was.

There has also been some converstion about the main wheel on the site
as well.

On Sep 7, 1:09*pm, Mark Wilson wrote:
I have a Russia AC-4C glider (with a retractable main gear), and need
new inner-tubes. *The sizes(47 x 110 for the tail wheel and 310 x135
for the main) are not available. *Does anyone know of an alternate?