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GEAR SPEED/SHIFT CALCULATOR

I have seen a few of these across the Internet, so I did some homework and figured out the math. I also included a little shift point guide at the bottom for those of us that do acceleration runs.

Use the size of your drive wheels (rear in most cases) and use decimals for gear ratios.

The example numbers are the values for the 2004 my330i ZHP Project Car

Enjoy!

To calculate MPH at various RPMs in each gear:
TIRE WIDTH (in mm)
Example: (255/35-18)
ASPECT RATIO
Example: (255/35-18)
WHEEL SIZE (in inches)
Example: (255/35-18)
1ST GEAR
Example: 4.35
2ND GEAR
Example: 2.50
3RD GEAR
Example: 1.66
4TH GEAR
Example: 1.23
5TH GEAR
Example: 1.00
6TH GEAR
Example: 0.85
FINAL DRIVE
Example: 3.07
RPM REDLINE
Example: 6800 - NO Commas, default is 7000
 
TORQUE PEAK
The RPM where you want upshifts to land*

* Since you want to utilize the maximum amount of torque your engine can provide, you may want to subtract 500-1000+ RPM from your exact maximum torque peak field to broaden the powerband you will use while accelerating. This will keep you in your engine's "sweet spot" longer.

RPM1st2nd3rd4th5th6th
8000000000
7500000000
7000000000
6500000000
6000000000
5500000000
5000000000
4500000000
4000000000
3500000000
3000000000
2500000000
2000000000
1500000000
1000000000

These calculations are based on mathematical formulas for circumference and rotating distance over time. There are many factors which can affect the real-life performance such as tires, weight deflection, shift delay, etc. Your results may vary.

The shift calculator is based on upshifting from a lower gear to the next higher gear at the same speed ensuring that the shift drops the engine speed to the torque peak RPM given, if possible. High torque peaks result in a shift at redline. Since powerbands on most engines cover a larger area than a single RPM point, again, your results may vary.

This is for entertainment/information purposes only and should be used accordingly at your own risk!

  © 2001-2008 MarvelPhx