Originally Posted by mihlbach
If you've got an old 27" conversion, I'd stick with 27" wheels. I'm afraid to put 700cs on mine. In fact I'm building up a new wheel set with new 27" inch rims...some are still making rims of that size, so there's no reason really to go with 700c. With 27X1 1/8 tires (or wider), the wheels are noticably taller than 700cX23. Plus, if you are tall and have a really tall frame, the taller wheels make the bike look better.
Of course it's going to make a big difference if you go from 27 x 1 1/8 to 700x23 - but if you stick with a similar sized tire, it's still only 4mm. My road conversion is a Nishiki built for 27" wheels, on which I'm running 700c x 28mm tires, and soon to go up to 32mm tires when these wear out. You gain a bit of clearance for fenders, and I've never had a pedal strike