Originally Posted by
masi61
The 58 has a taller headtube (206mm compared to 181 mm) and a 1cm longer top tube. Do you like to get a little lower and have no neck or back issues? If yes, the 56 might be a bit quicker. If you need the extra headtube height for comfort then the 58 might make riding the drops a bit more comfort oriented for you. In that case you would also need to consider what stem length or handlebar drop you want.
I don't have a very flexible neck. Meaning, the more stretched I am over the top tube (tank in a motorcycle), the harder it is for me to flex/pivot my neck upwards.
This is why I went with the 56. I was less draped across the top tube.
Thank you for your input.