Originally Posted by
John Hood
There are probably dozens of ways that it could be standardized that would make good sense so long as it were simple, uniform and informative. What's amazing is that hardly any of the common tire sizing standards are any of those things. You'd think that at some point someone would get it right and then everyone else would jump on the band wagon.
The issue is that with much of the marketing being US based they keep inventing new inch sizes rather then simply using the existing size designations, which are metric based. Things like the new 27.5 inch designation for 650B (ETRTO 584) and 29" for (ETRTO 622). The question for Joe Blough is whether he has a $49 bike or a $49,000 bike is no matter what the designation, what is the smallest and what is the largest tire that will fit. This is where the sizing systems, no matter which one is used, fall apart. Including ETRTO.
Perhaps the best designation would be this:
Bead Seat Diameter, plus 2 letters designating a width range of tires, for example A = 17mm, B = 19mm, C=21mm, D=23mm, E=25mm, F=28mm, G=30mm, H=32mm, J=35mm, K=38mm, L=40mm, M=45mm, N=50mm, P=55mm, Q=60mm, S=65mm, T=70mm, U=75mm, V=80mm, W=85mm, X=90mm, Y=95mm, Z=100mm+
So a rim might be marked as 622CH meaning that it's designed for a tire that is 21-32mm wide. A bicycle might be similarly marked as 622CK where the frame and components are designed for tires as narrow as 21mm, or as wide as 38mm. By moving to letter sizes, you eliminate the inch/metric issue.