rito25

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?

bbattle

If you still have the original steel wheels, I'd get some new 27" alloy ones. Shorter cranks is a good idea, there are 165mm cranksets but start with the new wheels. The old steel rims aren't hooked so you can't put a lot of pressure in the tires and they don't brake as well as aluminum, especially in wet conditions.

https://www.sheldonbrown.com/harris/wheels1.html#630

https://sheldonbrown.com/harris/tires/630.html

Narrower tires won't necessarily be any faster. I'd stay with the 1 1/4"

rito25

I have a new alloy flip flop rear. An araya alloy in the front. The one in back is hooked I believe, the one in front is not hooked. Wouldn't narrower tires be faster due to higher pressure?

TejanoTrackie 

There are a lot of factors affecting tire rolling resistance, and to some extent running tires at higher pressures will reduce rolling resistance and make them feel "faster." I doubt you'll notice much difference going from 27 x 1-1/4 down to 1-1/8 tires and you will increase the chance of pinch flats, since your typical 27" rim is quite wide.