Originally Posted by
Puget Pounder
You have the experts in this thread (of which I certainly am not)... but from what I gather, there is nothing inherently/physically better about 650B vs a 26". When you convert a 700c road bike to 650B though, you get that road geometry with the pneumatic comfort of the puffy tires. You also free up room for comfort. From my experience converting rigid MTBs/hybrids to drop bars, the handling and fit is kind of odd. Lots of people have done it and have had good results though.
This pretty much sums it up. With 650B, you can take an off-the-shelf 700c road frame with a geometry you like, shrink the wheel diameter slightly and make up for it with puffier tires. That's about the only advantage of 650B.