Singlespeed & Fixed Gear - Frame size?

How do I know what frame size is right for me? I'm 5'8" with a 30" - 32" inseam. The cross check I have has a 52cm frame, but I'm not even sure what that measures. I know it's the right size for me, but I've seen other guys who can buy a range of frames with about 6cm difference.

What is that measurement anyway?

Suggestions?

Originally posted by Yuppie
....but I'm not even sure what that measures. What is that measurement anyway?
Surlys are measured center to top which means from the center of your crankbolt to the top of your top tube, measured along the seattube. My Steamroller measures 53cm C to T as shown in photo.
Some frames are measured C to C...center to center (center to center of top tube).....in this case, my frame would measure 52cm C to C. And to make matters more complicated, some manufacturers measure their frames center to top of seat collar such as Cannondale, for example....

some manufacturers don't even measure along the seat tube.
i have a felt road bike size 58 and the seat tube measures about 54cm C to C.
it looks like they measure the length of the top tube, since my top tube is 58cm long...

ShrimpX.......Felt measures their frames from center to top of seat collar. I'll bet the distance from center to top of seat collar on your frame measures 58...

hm...i'm 5'8" and have a 30 inseam or there about as well. my two bikes are 53cm and 49cm
i got them both used cheap. if i buy new i would op for a 51 or 52. it really depends on
your liking and your body proportion. i have a longer torso than average so the 53 is cool for
the longer top tube. i use a longer stem with the 49. smaller frame usually have steeper
geometry (aka track geometry) therefore it might be better for fixie conversion (quicker handling)
if you are buying a track bike, i would go for a 51(c to c) if you getting a custom, i would have the
store measure you.