Originally Posted by Sixty Fiver

This is why so many people are confused by tyre sizing... those wider 622 tyres that are produced by Schwalbe (and others) may also have a fractional measurement of 28 inches on them as this is also the standard tyre size on most non British roadsters that may also be labelled as 28 by 1 3/8 & 1 5/8 (Canada) or as 28 by 1 1/2.

Those British roadsters run a 28 by 1 1/2 inch tyre which actually sits on a 635 mm rim and are not interchangeable with the continental 28 inch tyres.... for this reason they are called English oversize although their height is effectively the same because of a shallower tyre depth.

In the French system a 635mm rim is a 700B.