Im 6ft 3 I ride a 58, my friend who is 6ft rides a 58, we both can fit on 56s. Depends how cramped and race ready you want to be. If you cant get a good pedal stroke with you legs at less than 150 degrees when fully extended and when in the your forearms/upperarms dont create a near right angle. You may want to look to get professionally fitted because you make have weird dimensions, like I do. Ive got the legs for a 61cm bike, but the torso for 56/58cm bike.