What is the 56cm measurement referring to? I have a 57cm Pinarello & a 60cm merckx. The distance from crank center is to head tube is shorter on the Pinarello. Geometry is a tricky thing which can't be determined by a general or brand specific number. You really need to break down the frame geometry to figure out the horizontal length of crank center to bars. I can't tell you what you should like. However I tend to think a 120cm stem length is a good place to start in factoring frame size.