I understand 590mm is still a popular size in Japan. I need to ask someone who lives there if that is true. Anyone?

I was thinking about contacting a wheelchair supplier. See this https://www.draftwheelchairs.com/faq...-wheel-sizing/

"Why then is a 25″ wheelchair tyre marked 26″ when its only 24″ ¯across?

Similarly, the American rim size ETRTO**-559 has existed over there for generations, but has only recently become globally available through its use on most adult mountainbikes. These can still have fat tyres over 2″¯ wide, similar to the fat balloon tyres fitted to this rim size 50 years ago. This gave an overall wheel and tyre diameter close to their nominal 26″(559+(2×50)=659mm/25.9″), so was marked 26″.

However, when fitted with a typical 25mm wheelchair tyre the 559mm wheel size comes out a lot smaller than either of the names by which it is known: 559+(2×25)=609mm/23.9″.

This 559mm US rim size falls very conveniently between two British rim sizes which have been widely used on wheelchairs but are now almost extinct in the cycling world: 24 x 1 3/8 (**-540) and 26 x 1 3/8 (**-590). Fitted with a smaller section tyre for wheelchair use, they are sensibly known as 25″ as they fall roughly halfway between the existing 24″ and 26″ sizes, but you’ll get strange looks if you ask for a 25″ inner tube down at the bike shop".


597mm.....I can dream that somewhere, someone is using them for some obscure reason! LOL