Right now I'm on an old 58cm Trek road bike(because it was given to me, it's probably a bit big). I should probably be on a 56cm. I bought a new TT bike for triathlons and ended up on a 52cm QR Kilo. Its a nice bike and fits real good surprisingly. The 54 Cervelo was a bit too big for me. I think I have long legs and a short torso. Just be sure you get a good fit before you buy.