On a thread some time ago, I had this conversation with Tom A about lower BB bikes and lower Cda. His view was that moving the rider down in the space had almost no impact on Cda. Basically you're just putting an extra cm of frame inside the dirty air around the rider's legs/body which if I recall correctly he felt would be close to negligible. Not sure if it really is or now. Would be interested in hearing Damon's views as Cervelo no longer has to market its high BB decision and in fact, going lower than most of the competiton should be able to explain the reasons why...maybe it is handling, maybe it is aero.
When we discussed this some time ago (the high BB on the older Cervelos) Rappstar felt that it was because the low BB would result in a really short head tube if the goal was the get the rider low enough. Of course, that we with traditional headsets and stems, so different picture on front end air flow compared to the new gen of superbike designs. The new designs allow you to go with taller head tube and get the same relative pad placement.
When we discussed this some time ago (the high BB on the older Cervelos) Rappstar felt that it was because the low BB would result in a really short head tube if the goal was the get the rider low enough. Of course, that we with traditional headsets and stems, so different picture on front end air flow compared to the new gen of superbike designs. The new designs allow you to go with taller head tube and get the same relative pad placement.