Originally posted on 05-18-2010

Did some maths. Never a good idea…

Thank god for Flyin’ Miata’s gearing calculator:

Current gearing:
195/50/15 RE11 (22.7″ OD)
mph @7750 rpm
1st 38.4
2nd 64.4
3rd 91.2
4th 121.6
5th 149.4

Though I’m going to a torsen, the R&P ratio is staying the same at 4.3:1, so the only change is about 2.7″ of tire diameter (and a crap ton less wheel / tire weight, a crap ton closer to center-of-mass)
mph @7750 rpm
1st 34.1
2nd 57.0
3rd 80.8
4th 107.7
5th 132.3

So, there’ll be more shifting to 3rd gear, but 3rd gear will be a lot more usable I think, instead of now where once I shift to 3rd on a fast autocross course, it’s pretty brief and really just to keep me off the limiter for a few seconds. Also, thanks to the gearing the tires will give, we’ll be able to get to those speeds a lot quicker. I’m pretty excited to just feel the difference that going to a tire package that short makes

And, you know… the grip

EDIT: These numbers are at a raised rev limit of 7750 or so. I’m not sure I want to go too much higher than that with the stock valvetrain (once we’re talking solid pot lifters and stiffer valve springs, that will likely change)


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