Originally Posted by
dddd
I read just today that Dunlop introduced the 27x1-1/4" tire/rim size in 1935, and it was an entirely new set of dimensions not based on any other of the numerical "A, B, C, etc" versions of metric or other existing standards.
It was also stated that the 700c/622 bead seat diameter did precede this 27" standard, using fat tires of 1-5/8" and 1-3/4" to yield rolling diameters in the 28" range.
Likely this is how "700c" racing tubulars came to be referred to by tire maker Continental as 28", not that these thin tires measure anywhere close to that rolling diameter.
The 622 bead was a Canadian standard from around the turn of the century albeit on wooden rims. I mistakenly thought the Dunlops were early 50's. Still, I was wondering when the tubular racing wheel took over the peleton.