Now that 29″ wheels are completely accepted into mountain bike design and culture, with 26″ wheels holding their own, clearly the time is right for a new, even better, wheel size. 27.5 inches! No, I’m not kidding.
Might as well get ready for the talk of 650b. It’s already begun… Rivendell has been pushing for these in-between wheels as a touring and general riding solution for us all, and Kirk Pacenti of BikeLugs.com introduced a 650b mountain bike and has managed to get tires in production. The parts are all there, what about the hype?
The 650b standard is an old Euro thing that is pretty much right in-between 26″ and 700c/29″sizes. Touring folks like them as they allow an outside tire diameter close to 700c yet with much more volume. Mountain bike proponents point to them as a solution to many of the geometry challenges 29″ wheels present, both in terms of riders less than about 6′ tall and those designing suspension systems. Market forces will sort out if these things are “needed” or not, but I speculate the talk will intensify before it dies down. Between the touring folks and the not-quite 29er folks, there might be yet another size with a fighting chance.