Originally Posted by
JAG410
700c's are smaller than 27", so the only qualifications are long reach brakes, which are easy to find. Dropout spacing matters as well, depending on how many speeds you have/plan on having.
The difference in diameter is 8 mm, so the difference in radius is 4 mm. If there's enough room in the brake shoe slots for both the front and rear brake shoes to move down 4 mm, you don't need a new set of brakes. All you need to do is install the wheels and position the brake shoes once the wheels are secure. It doesn't matter if teh shoes can't move down any farther once they are adjusted for the 700Cs. So rather than run out and search like heck for long brakes that have nut mountings (this will be hard if you don't want Weinmann or DiaCompe centerpulls), or start modifying your frame for recessed nuts, do a test fit and see if the existing brake calipers are ok. They really might be ok.