Ok I must chime in here.......BMW does not messure there HP rating form the wheels....the messure from the engine (fly wheel). This i know because I work for a European car parts wholesaler. I deal and talk to BMW al day and i decided to call my vendor and my dealers about this issue. I even E-mailed my BMW contacts in Germany they all say they messure at the Engine.
So I hope this clarifies things...and the HP rating for the M5 is 395 hp. Although some top 400hp. Freak M5's. the M3 is 333hp to the engine. And with BMW's subtract 18 to 19 percent from the engine HP and you will get an estimate of wheel HP. if you want to be more exact its 18.9523%.
I hope this helps!
Roz
