This thread is pretty funny. I like the VSG talk
Some notes.
Pressure drag increases with the square of the velocity (assuming all other things are constant). Viscous drag is more difficult to predict and at low mach numbers viscous drag is on the same order of magnitude as pressure drag, so you can't ignore it. Most people use the coefficient of drag as a way of characterizing the shape of the car and the viscous drag at a certain Reynold's number. But the coefficient of drag the automobile industry gives is completely useless for any sort of drag prediction calculations.
The one thing you can count on is that at a given engine RPM and gear ratio, you'll be doing a specific velocity in the car.
Expansion of the tires isn't really worth determining since it'll be very small compared to the actual tire radius.
Of course RPM limiters also get in the way, along with speed limits and police. Then you also have to worry about speedo error which in BMWs always indicates higher than actual speed.
So, what does this all mean? In a vacuum you can easily calculate the maximum theoretical speed of a car. In reality, it's much harder to predict, depending on weather conditions and wind directions and whether you're going up/down hill or on flat ground, are all going to affect the maximum speed you can achieve in the car.
So the best way to figure out how fast your car will go is take it some place without speed limits and find out for yourself and take your GPS to measure it