Originally Posted by
70sSanO
While this is a bit OT, if 26” is 559mm bead diameter and 650b is 584mm bead diameter, that is a difference of 25mm (1”) in diameter.
How did the industry get to 27.5?
I’m pretty sure it is just marketing to fairly uninformed consumers that wanted a size right in the middle of 26” and 29”.
Not exactly 'uninformed' but 559 MTBs were and are most commonly referred to as
26" probably from their Schwinn / Klunker origins. Nobody has ever, outside of the pedantics at BiekForums, referred to them as 559's. There have been occasional '700c' (622mm) MTBs appearing as far back as ~1991, but the y2k-era
29" moniker better describes how it's different from a 26er, than '700c'.
Same for
27.5", which is really 650b, but again, tells you much more easily that it's bigger than a 26er but smaller than a 29er.
With the trends towards wider rims/tires in the gravel/adv segment, the line's getting blurred, but generally, "29er" has referred to 622mm wheels for all-terrain tires wider than 47mm or so (1.75" for you MTBers), and "700" for narrower, pavement-biased tires. Same for 650b -v- 27.5"