I've thought about doing it on older MTBs with drilled steerer and seatstay bridges but haven't gone to the trouble of sourcing the brakes I'd need for it. Seems like fairly standard reach road calipers would work on the fork of my Mongoose. They'd have to be nutted and the bolt would have to be long enough to accommodate the 1 1/8" steerer.

That's about as much thought as I've put into it.

Oh, I do have a 700c rear wheel on my cheep-o Black Baron bike, but I haven't fit a brake to it.


Black Baron Day 8 by Lester Of Puppets, on Flickr