Fine-tuning your final drive is one for the easiest and cheapest performance enhancing alterations you can make on your motorcycle.
Final drive sprockets offer a quick and easy way of changing the gearing on your motorcycle. You can change the countershaft and/or rear sprocket giving you a wide range of gear ratio options. Dirt or street racers will already know the importance of gearing a race bike correctly for each track and track conditions.
Street riders may wish to alter the gearing to move a bad vibration period up or down in the speed range, or you may wish to have a bike with more “snap” or off the line power (higher numerical gear ratio) or turning less rpm at high speeds (lower numerical gear ratio).
Calculating your current gear ratio is easy to do just count the number of teeth on your front (countershaft) sprocket and the number on you rear sprocket. Use those numbers and the chart or our gearing calculator you will find your gear ratio.
Example: Front 14 tooth, Rear 43 tooth
The example above gives you the ratio between the front and rear sprocket, it is not the overall ratio. To obtain the overall ratio, you will need to multiply the primary drive ratio by the top gear ratio by the final drive ratio between the front and rear sprockets.
Finding the correct ratio for a new track is a trial and error procedure. If you cannot alter the individual gear ratios in the gear box you may have to settle on a compromise. Accurate notes should be kept for comparisons to be made. Weather conditions and track surface conditions all play an important part in selecting the correct gearing for the lowest lap times.
With the ability to change both sprockets you have a wide choice of gearing and the acceleration effect on the bike. For example if you are already at a 15 tooth front sprocket and need to gear shorter (higher numerical ratio) and don’t want to use a smaller front sprocket then you can use the chart to select a rear sprockets to produce almost the same result that you are looking for.
As a rule one tooth less on the front sprockets is the same as 3 teeth less on the rear sprocket.
When you change the gearing you may have to alter the length of your chain. A good rule of thumb is to figure the difference between the old number of teeth to the new amount of teeth. Divide the difference by 2 and then add 1. For a more in-depth look about a motorcycle chain please visit our chain page.