Gear Ratio

Curious to know

the rule of tomb when determining the best gear ratio in your gearbox for your track (Road Race )

The gear ratio with the most torque to the drive wheels will deliver the maximum acceleration as long as the wheels don't slip. The top gear (and/or final drive ratio) should be selected with the maximum speed you will need to see occurring just beyond the power peak.

Usually you are constrained by available gear ratios for a particular gear box.

I wrote an app for the iPhone/iPad that calculates the torque in each gear for a given engine, then figures out at what RPM you should shift to maximize the torque to the drive wheels. I use this info to program the gear-dependent shift light on my dash. If interested, search the Apple App Store for "Shift RPM"

David is "Shift RPM" app available only for iOS ?

Yes, I looked into creating an Android version, but have just been too busy. Before I wrote the app, I used an excel spreadsheet. I'm attaching that in case it would be useful for you. This version is setup for the Hewland Gearbox -- I have one around that works with Porsche 901 gear boxes (allowed you to enter the gear id letters).