650 wheels on a cross bike?

[Cataboo]

How about 650b's?

There are brake adapters that allow you to put 700c's on a mountain bike... There's a set of paul bmx brakes for that allow you to run 650bs or 700c or 29er rims - they have more adjustment.

If you get disc brakes, you can swap between 650b & 700c wheels without any problem.

I was looking up building up a rawland's sogn for a long time because of the amount of versatility in the frame to run whatever size wheel you wanted - but finally decided if I really wanted to do that, I'd get a surly steamroller fork for my surly pacer & use long reach brakes to run 650bs on it & swap to 700c's. Cheaper than building up a new frame.