Originally Posted by Loose Chain

Do not get hung up on the alleged manufacturer stated frame size. Measure the effective top tube length, that is the frame size c/c. Most people, of fairly average proportions can accommodate a range of fit of up to plus or minus 2cm. And some people prefer a competition fit and some a French fit or something in between. At 5-10 plus and 33 inch true cycling inseam, a 56cm c/c is my size but my current favorite bicycle is a old GT that is a stated size 54cm but measure a full 55cm on the top tube and fits me like a good glove, when adjusted out for me, it gives me a good, preferred somewhat aggressive fit and does fine for even longer rides. I have a 56cm in the same bike, it feels a little big to me, not as quick, both will ride hands off under power.