26" wheels for 650mm frame?

[bert]

Argh. I just unwittingly bought a 650mm Ti time trial frame on ebay thinking it was a regular road frame. Well, at least it was fairly cheap. Does anybody know if these 650mm wheels, which are pretty nonstandard are interchangeable with MTB wheel (26in=660mm)?
Would these tiny tired things make a pretty decent cyclocrossy road bike for on and off road cycling?

Also, how skinny do MTB tires get? 28mm? 35mm? I will probably have to see when the I get the frame what sort of clearance I need.

[rainperimeter]

650b is slightly larger that 26"? if i remember correctly. it seems that with proper brake alignment they would be interchangable. i believe it should be no issue. i think the narrowest/smallest 26" tires get down to is 26x1". that's pretty road-y. 650 tires are by no means impossible to find however.

it's been a while since i've dealt with anything beside 700c so someone may come along and correct me (i worked in a recumbent only shop and many bikes we sold/tuned/repaired had 26" or 650b wheelsets, but that was a couple years ago...)