AMuzi wrote:

'700' started out at 642mm (historically
measured like wagon wheels at the very
outside diameter, 700mm). As roads improved
and tires narrowed, a new smaller lighter
version of 700 at 635mm appeared so the 642mm
became "700A" and the new one "700B".

So that's the origin of all the 700s! 635 and
622 are still around, the 622 being the more
common of the two it seems. But "there is no
queen of tires", right?

(Since everyone just made things up to suit
their need/desire, there were two 700B, both at
1995mm=635mm and 1992mm=634mm)

The circumference. Historically measured
like... windmills?

Lest you think that we moderns are more
rational or smarter than The Ancients

No one is thinking that. Ancient morons make
modern morons...

note that your example of 650B was known as
a 26" size (26 x 1-3/4) for a hundred years
and nearly died out before being rebranded as
'twenty seven and a half' because it's in the
middle of the 26" tire range and smaller than
27 inches.

Why wasn't it rebranded "twenty seven minus
a half" rather?

--
underground experts united
http://user.it.uu.se/~embe8573