The issue of the availability of several type of tires remain:
- 24"/ETRTO507, BMX size, mainly wide tires, no road tires.
- 24"/ETRTO520, very few tires, mainly road tires. This size is (was) used for road bikes for smaller riders for instance by Terry and by Airnimal.
- 24"/ETRTO540 I don't know any recent bike using this wheel size?