Originally Posted by
VernonFlorida
I have read this entire 15 year-long thread, and I don't think I understand anything better than I did when I searched up the same question as the OP.
No fault of the posters, though people tend to add bits of extremely minute partial detail in dribs and drabs, probably based on their particular experience.
I think really you'd need a well written and edited book with diagrams to properly explain the history of and current naming conventions for tires and wheel sizes.
In any case, speaking of personal experience, I just installed a 45mm winter tire marked 28" on a rim marked 29, which I bought because I was told it was the same as a 700.
It fits fine! All perfectly rational
700c is an obsolete French designation, IIRC...
27" and 29" are badly named American marketing names related to Overall tire diameter, when mounted and inflated... and 28" is a bad English marketing name, along those same lines....
650b is a french thing.... again.... i think.... maybe.... kinda-sorta.
and the 700 or 650 specs simply don't exist, but are approximations of overall TIRE OUTSIDE Diameters... as are any INCH specs shown regarding RIM Sizes. 20" rims are actually about 15 3/4"across the diameter...., etc.
there are 12", 16", 18", 20", 22", 24", 26", 27", 28", and 29" bike tires being sold... with variations of Actual bead Diameters on several of those tires...
Continental and Schwalbe seem to being creating their own bead specs at times... the darn things refuse to bead up on the rims they were SUPPOSED to fit on... IRC made some of those too...
And then SCHWINN decided to create their VERY Own, Proprietary Tire Bead sizes and designs......
wanna buy some 22" Schwinn ROAD tires? oh wait... i tossed all but a few of those turkeys. People were attempting to sell them on 'Bay for less than shipping cost, with free shipping! $5 each.. shipped.
it was cheaper than the dump costs. Luckily, my local dump allows bike tires to be disposed of if they're in plastic trash bags, at the normal rates per load size....
i hope this adds to the confusions created by way too many stubborn folks bent on clinging to ridiculous specs that never really meant what they were supposed to anyway.. it seems that confusion was the only goal, at times.
did you know that 20 x 1.375" and 20 x 1 3/8" mean different things, in the bike tire world? they do.... fractional and decimal sizes denote a BEAD SEAT DESIGN and DIAMETER DIFFERENCE.... most of the time... but not always...
An ETRTO number shows Actual BEAD Seat DIAMETER, which is a MUCH Better spec to rely on.
i'm sure some hate ETRTO too... especially the stubborn folks.
(i still call "tubular" tires SEW UPS..
)