Originally Posted by
mickey85
You can get 27" tires down to 25c wide (Panaracer 27X1" comes to mind). To run it either fixed or singlespeed, redish the rear wheel (center the rim over the hub - look online), and screw on the cog. If you're running a fixed cog, buy red loctite, put it on the threads, screw it down, and mash the pedals a few times to get it on there tight. Then let it sit overnight, and you should be good. As far as chainline (very important on a fixed), check out
www.sheldonbrown.com for the info.
The reason it isn't safe to run a fixed cog on a standard hub is, as said before, it runs the danger of unscrewing; however, using the method above, I've never gotten one to unscrew - including the rather loosely fitting Surly cogs. This is on a heavy steel bike with steel wheels and rather wide tires (32c) and me weighing in at 220 lbs.
EDIT: You can run 700c wheels in this frame - you may need longer reach brakes (don't run a fixed gear without at least a front brake - especially with a standard hub) to accomplish that, but on frames of this era, I'd doubt it.
That's one way you can do it - keeping the wheelset you have now and not buying a new rear wheel.
Check what size is marked on the side of your tires. It will either say 622mm or 630mm somewhere on the side. 622 means 700c rims, 630 means 27" rims. If you want to save money and run a brake, go with what Mickey said. You could ride and save up for a new wheelset. Just don't do any massive skidding on it, or you may tear the threads and wind up being (literally) unstoppable.
So yeah, check wheel size and your budget. You can get thinner 27" tires, and 700c tires come in all sizes, down to the ridiculously tiny (19mm, etc) -- but I don't know that I'd recommend you go any smaller than a 23mm on an urban fixed gear. I'd just as soon get a 25mm or 28mm with reinforced tread and low rolling resistance. Speed of the wheel has little to do with tire diameter and more to do with the tire's tread.