random physics problem, been thinking about it for a long time, never got a chance to try it out
here it is:
as physics says, power = force X velocity. this leads to that top speed should take place at engine max hp output, when all the drap and friction add up to the force. But now, how transmission works show that the higher engine revs, the faster the car goes. Finally, engine peak output NEVER occurs at redline(max rev).
So, where exacltly is top speed, max rev or max hp
I know this problem has 2 answers, if your gear ratio is low enough, you just can not top out to redline.
what if the gear ratio is high?

 

If you are not limited by RPM you will be limited by power.

 

You have to remember that your engine and transmission are not separable for the problem.

Your gearing will effect your power to the wheels since it will multiply your engine power according to the gear ratio.

Ideally, for top speed, you would work out how much power you need to reach the speed (to overcome drag/friction, etc, etc). Divide that power by your maximum engine power and that will give you your gear ratio. There's a little more to the problem (okay, a lot more) but that's the "simple" answer.