Originally Posted by
walnutz
This thread has me wondering: what are the effective differences between, say, 650bx47 and 700x47 on the same frame, besides a higher BB?
Curious because I used to have a bike built for 650b that made me fall in love with the rim size. It was sadly stolen and now I have a bike that could accommodate both tire sizes listed above.
The problem with 700 x 47mm is that the tire/wheel combo has too large a diameter compared to something like 700 x 28mm, and will change the handling properties of the bike (it will become less responsive and a bit more of a sluggish feel to ride, especially climbing), more toe overlap, etc. The great thing about 650b x 47 is the outer diameter is approximately what 700C x 28mm would be, so the bike handles in the way that it would with 700C x 28mm tires, preserves the geometry, better toe overlap clearance, etc.
If you are really tall, you might prefer the large wheel/tire combination.