I have been reading about different bike geometry's and I would like to know if the frame size matters that much. I would like to buy a used bike either on through this website or on ebay. I am 5'7"-5'8". Most manufactures show that I would need a 54cm, but I could also fit a 52cm and a 56cm. Does anyone have any imput on this? When I search for bikes I usually find a lot of 56cm but not many 54cm. Will this 2cm make or break me? I understand it's about comfort but when buying online it's not possible to try before I buy. Thank you for all your help.
By the way I'm looking for a Trek 5200.