Originally Posted by ehcoplex

Yes, it is knowable..... somewhere! Apparently there was a blog post somewhere that had all the info in one place but it's gone now. I found the info I needed in various places and I could swear I wrote it all down somewhere, but now....

A 650B wheel will most definitely fit a frame made for 700c, as the 650B is a smaller diameter. The question is how much extra clearance for wide tires will it give you, and is it enough to be worth it. And what will you need to do as far as brakes. It gets a little more complicated as the width of tire you run will determine where exactly the widest point will be, as well as your overall diameter.

I've got to run now, but I'll see if I can find the numbers..... But I believe I determined that with 650B x 42 tires the widest point was about 303mm from the center of the wheel..... And I think the outer edge of 700c wheel is more or less where the widest point with a 650bx42 tire will be....