Formulas for MPH & RPM etc

[Rockabilly]

Thought I'd throw this in here so you don't have to search the net for info.
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Formulas for MPH & RPM & Gear ratios & Final Drives & Tire Diameters in Inches
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MPH = (rpm x tire diameter in inches) / (gear ratio x final drive ratio x 336)
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RPM = (mph x final drive ratio x gear ratio x 336) / tire daimeter in inches
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Gear ratio = (tyre diameter in inches x rpm) / (final drive ratio x mph x 336)
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Final drive ratio = (rpm x tire diameter in inches) / (mph x gear ratio x 336)
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Tire diameter in inches = (mph x final drive ratio x gear ratio x 336) / rpm
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Final drive ratio = Front diff x Primary ratio (in box)
eg: GVR4 front diff - (58/15) 3.866 x primary (37/29) 1.275 = Final drive 4.929
eg: GVR4 front diff / t/c (24/22) 1.0909 = Front combined ratio to > Rear diff ratio matching.
FYI The final drive ratio is the driving ratio, not the diff ratios.
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MPH to KPH = MPH x 1.609
KPH to MPH = KPH / 1.609
Inches to MM = Inches x 25.4
MM to Inches = MM / 25.4
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Cheers !

 

[EVOCPE]

Here are some specs, if anyone wants to know

VR4s and GSRs:
1.090 Transfer ratio (TR) (24/22)
3.867 (58/15) front diff ratio. (FDR)
3.545 (39/11) Rear diff ratio (RDR)
RDR x TR = 3.866 combined rear final drive
Total final Drive ratio TFD of 4.9333

EVO 1 and 2s:
1.090 (24/22) TR
4.266 (64/15) FDR
3.909 (43/11) RDR
RDR x TR 1.090 (24/22) = 4.264 combined rear final drive
TFD = 5.443

EVO 3
1.074 TR (29/27)
4.200 (63/15) FRD
3.909 (43/11) RDR
RDR x TR = 4.199 combined rear final drive.
TFD = 5.358

The total final drive TFD, is the diff ratio (front or rear+transfer) multiplied by the 37/29 (1.276) primary reduction inside the gearbox that occurs before the diffs

 

[Rockabilly]

Mike the TFD would be more correct worked out from the rear diff x t/c x the primary gears
because the rear tyres are going straighter through corners. The Evo 1-2-3 rear diffs are
overdring the front & the GVR4, GSR & RVR has the front overdriving the rear. Gets pretty
confusing when the viscous coupling is altering the drive. When locked it would be the TFD
worked out using the rear & t/c & primary because there is no viscous to make the rear slip
through corners. Straight would be an average between both TFDs if it is locked. Being locked
is kinda faster through corners, but Fark 3 point turns are a bitch lol. Ahh switchable.
Cheers !