Tune Gear Ratios

Eventually, choosing larger gears will only slow you down.

Gears do more than transfer rotational power from one source to another; they can adjust the rotational speed as well. That’s what transmissions and drive-lines do. Few people, other than road racers, experiment more with gearing combinations – for cars or motorcycles. You can begin with engineering data if you want. You can start with an educated guess. What is most important isn’t where you begin with your gear combinations; it’s the detailed and scientific process you employ to track the results of your experiments. That’s what produces optimum results, transferring engine power to your tires.


1. Try new gears and combinations of gears, systematically. Start with all the math you want, but the only real proof of an optimum gearing combination is in the results. Start with a combination of gears you think will work, then make minor and incremental adjustments, interchanging gears with slightly larger or smaller gears.

2. Record and compare the results of each new combination systematically and accurately. However you choose to test the results of your gear ratio combinations, keep a journal noting each variable that may affect your outcome. For example, if you’re testing gearing on a race track, don’t just record your times, record any other changes such as temperature that may account for variations in results.

3. Make your selections incrementally. For example, if you’re selecting motorcycle sprocket ratios, don’t go from an 18-tooth front sprocket to a 22, unless you have data based on your tests to believe 22 will be optimum. After you try an 18-tooth, try a 19-tooth and so on. This will help you plot more accurate results, which can produce more valuable patterns in your data, in turn resulting in better information to base your final gearing decisions on.

4. Isolate the primary gears and the secondary gears. From your engine’s drive-line, you will have a primary drive gear, then one or more subsequent gears. If you skip back and forth, switching out primary gears, then secondary gears or one specific transmission gears, the results may not produce valuable information. Isolating one type of gear at a time, such as primary and secondary gears, is imperative to producing useable data to make gearing choices.

5. Keep records after you’ve made your selection. Don’t just go through a round of testing, then make a decision. Keep race records or performance records, noting what your gear ratios are as they may offer you clues about continually develop optimum performance.