My S2000 seems to turn 3300 rpm at 60mph in 6th gear. This is confirmed by the data panel in R&T when it did its article a couple of years ago. According to the TireRack, the rotations of the rear wheel/tire (stock 225/50-16 S02 Bridgestones) is 840 per mile. Since the overall gear ratio (4.1 rear end and 0.81 sixth gear) is 3.32 to one, the rpm should be 2788! Doing the tire math for that size tire works out to only 812 rotations per mile. I understand that a loaded tire may not measure exactly the same as an unloaded one, and that various tire models may differ slightly in actual size. However the 20% error I see is too much to be explained by either of those things. I have done this math with countless cars using data from Road and Track or Car and Driver road tests, and the math always works out to within 5% of predicted by doing the calculations. For the S2000 the math is "off" a similar 20% for all gears. What gives???

 

1.16 final drive ratio?

 

No, final drive ratio is 4.1 to 1. Where did you get 1.16 number from???

 

The S2000 has both at 4.1:1 axle ratio and a 1.16:1 final drive ratio. Terminology may vary, but you have to use 'em both.

 

There is a 1.16:1 secondary reducer in the transmission. Thus, 6th gear is effectively 0.94:1, which gives you about 3.85:1 as a net reduction in 6th. Thus, at 3300 RPM, your net is (3300 Rev / 1 Min) * (60 Min / 1 Hr) * (1RevOut/3.85RevIn) * (1 mile/840 RevOut) = 61.2 miles per hour.

 

Final drive ratio is 4.1 to 1. Where did the 1.16 number come from???

 

Thanks!!! I guess it is unusual to have that secondary reducer, but it is the only explanation other than Honda using "rpm inflation" on its tachometer!

That does account for the "error" I was finding in doing the calculations. Is the 1.16 to 1 ratio gear prior to the six speeds, or at the back of the transmission?

 

It is applied at the rear of the transmission.