Originally Posted by
garysol1
Or are they just talking about BB/Stay stiffness. What I am questioning is front end stiffness when your cranking on the bars left to right. Will the thinner shaped down tube have more give than a round tube.
Depends on your assumptions, but generally, the biggest factor is amount of material away from the neutral axis. So if your aero tubes put a ton of material at the bottom of the headtube that otherwise wouldn't be there, that joint will be stiffer.
Of course, analyzing that joint in a vacuum is kind of worthless, since the whole tube bends.