Originally Posted by
Flying Merkel
The difference in diameter between 27 and 700c is 8mm. Most brake can handle a 4mm adjustment. Bigger question is the width of the dropouts. Old frames are a bit narrower than new standards. My old Univega had 126mm spacing. I installed a rear rim with 130mm. I just pushed the frame apart by hand a bit. Not sophisticated, but it worked.
+1 Good answer. I agree with the part about the frame on the old bikes being more narrow than newer wheel hubs/freehubs. This is especially true if your 700 cm wheelset has a 7 sprocket freehub.
You can try to spread the chainstay/dropouts a little bit with a car jack. Unfortunately, it isn't really that easy because you can spread the frame apart and still have interference with the chainstay tubes rubbing against the freehub.
You can give it a whack - you don't have much to lose.