How to Find a Gear Ratio for Racing Carsby James Shomar
Setting the right gear ratios is tedious, hard, time consuming an expensive. Most Formula One teams spend countless hours and millions of dollars preparing their car for a race. While unlike a Formula Team engineer your job might not ride on setting it up correctly, it is important to get the correct setup in order set consistent and fast lap times.
Setting the right gear ratios for a specific track
Step one the Control Lap: Take your car out as is for the first lap. It is important to run as hard a lap as possible so that you will know exactly what needs changing in relation to each turn. When running check to see what gear you are using for each corner and straight trying to almost memorize the track. The most important thing is to look at engine RPM at each corner. This can be done either by checking your tachometer while racing or more accurately if you have the ability to record lap telemetry.
Adjusting the Gears: When going over the telemetry or doing it by memory, remember how many RPM your engine was at at each corner. The idea is to make sure you reach maximum RPM just as you are about to brake into a corner. This allows for the maximum acceleration on the straight before having to let off for the upcoming corner allowing the car to make as fast a lap as possible. This will also help set up a braking point once your ratios are set correctly. Once you hit maximum RPM you know it's time to let off and begin braking for the upcoming corner. When adjusting the ratios, a bigger ratio gear will allow you to stay in the gear longer and achieve a higher speed in that gear. If you find that you are having to up-shift near a corner or hitting the rev limiter a few times, you will want to adjust to a bigger ratio for that gear. If you find that you are not at maximum RPM before entering a corner the solution is to set a smaller gear ratio. Although a smaller ratio means that the car can not achieve as high of speed in that gear, it will allow the engine to reach higher RPM quicker thus making the car accelerate quicker. Setting a smaller ratio is usually a little trickier than a larger because although a smaller gear will help accelerate if it is set too small it might reach top speed before you are at the braking point. The trick is to decrease by small increments and to balance the top speed with the ability of the car to accelerate to that speed.
Repeat: Go out for another lap with you gears adjusted and see what has changed. You might need to go back and vary them again if it is not set up correctly. Change ratios in small increments to make it as accurate as possible. On this lap, you might notice that while one set up is good for one corner but it might not be the best for another. This is a common occurrence in racing especially when planning out which racing line to take when driving. Try setting it up both ways and also try a medium or "compromise" setting and then decide which is better to use based on other corners and the over all lap times produced.
- It is important to set consistent laps throughout the adjustment of the gear ratios. If your laps vary widely it will be impossible to tell if it was driving error or gear ratios that need adjusting. Overall when adjusting ratios keep as many other things constant as possible so that it is solely gear ratios effecting lap time allowing you to adjust accordingly.
Things You'll Need
- Race car
- Adjustable gear ratios
- Race tack
- Ability to record lap telemetry is possible
- Do not set your ratios to an extreme acceleration or an extreme speed setting. Not only is this terrible for lap times but it could bring ware and damage to engine, transmission and differential parts.
James Shomar began writing professionally in 2008. His journalism experience includes automotive writer for "The Daily Orange Newspaper" and columnist for "Snarling Exhaust Magazine." He has been president/driver of SU Formula SAE Race Team, a Go-Kart racer, team-owner/driver for Rahmar Racing, test engineer for Sensis Corp. and in marketing/media development for Driver's Village Dealership. Shomar is a mechanical engineer at Syracuse University.