Am I going to have to have a "Motorcycle Education Class" for some of you guys? The most aerodynamic streetbike made is very un-aerodynamic. Whereas the Supra probably has a cD of @.31-.33 (VERY guesstimating that one, correct me if I'm wrong, I'm basing it on what knowledge I have of drag coefficent), the Hayabusa MIGHT have a cD of .38-.39. Get on a GSXR1000 and that number goes to about .41. As is obvious, a higher cD means the vehicle (or barn in most bikes cases) is less slick in the air and more prone to being slowed down by the air (less aerodynamic to shorten it!). Most bikes have a drag coefficent that is the equivalent of a van or large truck.