I'm feeling quite fortunate that I generally have proportional body dimensions. I have a 32.5" inseam and my original height (I'm older and shorter now) was 5'10 1/2". For my entire 40 yrs of cycling a "square" 55 (55 ST and 55 TT) has been perfect. I can ride anything from 54 to 58 pretty well but 55 is the sweet spot. Find your sweet spot. I found mine using the LeMond-Guimard sizing formula. I've also had a professional fit which confirmed my findings.