Originally Posted by
Hypno Toad
My surprising take away is that the Felt (newer AL frame) has such an advantage on the Mondonico (classic steel frame). The Mondonico is the new (to me) bike and that may be the fact that I haven't ridden it as many times. Plus I spent last summer making lots of little tweaks and upgrades, so many of the rides were shake-down rides, not aggressive rides.
Do you have identical tires on both? There can be 20W difference at 20 MPH between OK and good tires.
Is your position identical (including bar width)? 75-85% of your aerodynamic drag comes from the meat bag on top of the bike.
Do you have similar wheels? There's a significant difference between classic box-section and even vaguely aerodynamic modern rim shapes.