Originally Posted by
Brian Ratliff
The 2cm difference in frame size is all front end. Wheelbases are mostly identical, which means seat tube angle is pretty close, within half a degree. All the difference is at the front end.
I would suggest that your saddle is not for you. If you are struggling to use a saddle that requires you sit forward of where you are supposed to traditionally sit on the saddle, then perhaps it's the saddle itself, not the setback, that is the issue.
If you're comparing sporty racing bikes, maybe you are right, I don't know. But I have bikes with STAs ranging from 74.5 to 71.5, and the effect is quite dramatic. At 704mm seat height, the amount of setback variance (47mm) is well out of range of most seatposts. It's certainly enough for me to sell the 74.5 frame, given my preferences.
Regarding the saddle, you may well be right. I hope not, because the 'comfy spot' really is very very comfy.