Cool, excellent, great information, but let's pause to note that we're posting on the Touring subforum, and for a cycletourist on a long journey, this crosses the river from 'common' to 'available'. I can get 17" (yes, seventeen inch) tires for my Moulton bike delivered to my door in a day or two as well, but no one would call them common.

I've opined before that if I were bumping down the road on a duct-taped tire knowing I'd have to spend a couple of days in a grim little hamlet in flyover country if I couldn't find a tire in the general mercantile, I'd want to be on 20"ers (ISO406mm). I'd think this would be the case in any country where children rode bicycles or where delivery/cargo bikes were in use.