I am converting a Gitane Gran Tour DeLuxe into a fixed gear. This bike's bottem bracket seems to be fairly low. With 27 in rims and 27 1/4 in rims and 171 mm cranks. I think my clearance will be fine; however, I was tempted to try to upgrade to 700c rims. I tried my brother's wheel set which was 700c x 23 or 28 and I had almost no pedal clearance. If I wanted "faster tires" what is my best bet? Try 27 1/8 in tires? Get shorter cranks?