mill4six wrote:I see, more to think about then. In response to an earlier question, I suggested 650b wheels so that I could have knobbly tyres on one wheelset and a second with deep rims and slicks for road use although I have found slick 25mm 26" tyres before it's not as easy.
25mm 700c has essentially the same diameter as 26" x 2.1 or 2.25 and will therefore deliver the same bb / pedal ground clearance and design geometry, and would also give you the best possible choice of road and off-road tyres money can buy. So if I were you I wouldn't go for 650b.