Okay, so axle ratio usually = final drive ratio. That's simple enough and easy to understand. However I think this website means something else by final drive ratio, or (as they say it) transfer ratio:

http://www.turnzero.com/technical_resource...gear_calculator

I tried looking up this "transfer ratio" variable everywhere to no avail. All I can conclude is that it's a lot more complicated than I thought, and I think it might have something to do with drivetrain efficiency, because those theoretical top speed figures seem pretty accurate. If you got rid of that variable the S2000 would have a theoretical top speed of over 190 mph. Oh and one more thing, I've searched everywhere, but what the hell is the "official" top speed rating of both AP1 and AP2 S2000s?

 

With the S2000, there's the ring and pinion gear in the diff that's commonly called the "final drive." There's also something called a "secondary reduction gear" inside the the transmission as well. The website seems to have those switched from how I personally would use the terms, but it doesn't really matter what they're called - they're still used the same in the calculations.

Far as I know there's no "official" top speed. But it's generally accepted to be around 155mph on flat ground without a tailwind. For both AP1 and AP2.