Originally Posted by
chas58
All other things being equal (including tire width), the 650b will lower your bottom bracket significantly. The biggest issue there is probably pedal strike,
although theoretically the bike will be more stable when it is lower. If you run a small frame, toe strike may be an issue with large 700c tires (and more so if you plan on running front fenders).
like
mstateglfr said, most people run 30-45mm tires in 700c, and 47mm up in 650b.
My advice - stick to the
tire diameter that is as close to what your bike was designed for (what it comes with stock). This is going to give it the best handling dynamics and optimum height.
If you spend any amount of time on pavement this is a big deal. 700x40 feels way different than 700x23/25 if any of you swap to skinnies regularly. 650x40 puts you at a similar diameter if you're riding a more roadish gravel bike and mellower terrain. A local runs 650x38c on his OPEN UP at our local crits and is still fast and can ride it home afterwards down the rail trail. He says he hates the way it feels with 700c wide slicks