[Richard230]

Here is a link to an interesting article regarding calculating aerodynamic drag for a motorcycle chassis. Not something that you come across every day.  It might be of interest to someone who is trying to make their motorcycle more efficient or just likes this sort of thing: 

http://info.simuleon.com/blog/how-to-calculate-drag-coefficient-for-motorcycle

[simca1200scoupe]

Interesting stuff 

I have another formula which is not too bad for some rough calculations:

max topspeed = 45 (seated driver) or 48 (driver nose down) * 3rd root (engine power in hp at crank)

example:

seated driver on a 27 hp bike = 135 km/h max speed.....not far away from the data of a GT !

The factor 45 or 48 includes the average air and rolling resistance and is suitable for some first calculations......