Hi Frank
I've just rec'd the M41 metal wheel set from RCtank.de, they are supplied with Tamiya M26 rubber tyres - 56015, A901080.
They fit a wheel 35mm across, and 9mm wide, though the 35mm does not include the flange which holds the tyre in place.
This being for single wheel of the inner & outer wheel pairing.

Hope this helps?

Mal