Originally Posted by
NormanF
There used to be a bewildering variety of tire sizes but they seem to have sorted themselves out into more or less five categories:
406 mm for folders, mini velo and bmx bikes, 559 mm for cruisers and standard mountain bikes, 584 mm for mid size mountain bikes and older French touring/city bikes, 622 mm for road bikes and 29er mountain bikes and 635 mm for path bikes and roadsters.
Dont forget 507mm for 24" kid MTB's, 571mm for 650c (26" narrow road tires) both are fairly common. There are also a couple of other 20" wheel sizes that all use different rims. I
nterestingly, the outer diameter of the tire for both 507mm and 571mm are very close. I converted a 24" mtb frame into a road bike for my daughter by switching it to 650c wheels and fork and drilling the frame bridge for a road brake on the rear tire.