Thanks Melgar for the link to the MTH traction tyre chart. I have an Australian built "Ferris" tinplate loco and tender from the 1950's, and I also am searching for new traction tyres for it. I have attached a couple of photos of the 4-6-0 loco, and the tender, and you will note how the tender is the "driver" and the loco is just a "free-wheeler". That's the way it was built here in Australia, but I also know they did make the same model with the 20v AC motor inside the loco chassis instead of inside the tender. We're a bit crazy here, "down-under".
Anyway, I think I have found the right traction tyre for the drive wheels in the MTH chart you posted. I've been searching for the correct size tyre for ages, to no avail, and have had to make do with stretched "O" rings......not the best for keeping the tender correctly positioned on top of the brass 3 rail track.
Thanks again, and I'll be getting in contact with Midge at MTH to place an order.
Peter on the fabulous Gold Coast, in sunny Queensland, Australia.