How changing your bike’s gearing with a sprocket change could be a smooth move.
You love your bike. But the continuous vibration at certain speeds can be a real buzz kill. Fortunately, a relatively simple change of final drive gear ratios on your chain-driven motorcycle can move that bad vibration away from the speeds you travel most and restore the good vibes you otherwise get when riding your machine. It’s relatively easy for the average rider to do or have done by a qualified mechanic at a reasonable cost. First, let’s get a better understanding of what this whole “final drive gear ratio” thing is all about.
Get on the drive train.
The main purpose of the “drivetrain” is to move power from the engine to the rear wheel and to make sure that the right amount of torque—the “grunt” your engine provides to get things moving—is delivered as needed. This is what’s called “gear reduction” and is largely determined by the size of your bike’s front and rear sprockets.
The factory engineers established the best compromise of power delivery and overall performance at all speeds for the average rider. Unfortunately, with some bikes, that results in an annoying vibration at certain travel speeds as a buzz in the handlebars, footpegs or other part of the bike. For the rider who spends time traveling at highway speed, that can mean numb hands and feet or even pain after just a few minutes in the saddle. So, what’s a rider to do?
Your bike’s gearing ratio is determined by the relationship between the size of front and rear sprockets. This ratio determines what the engine speed (RPM) will be at various travel speeds. By changing the sprocket size on either the front or rear sprocket—or both—will change the ratio, lower or raise the engine RPMs and adjust the amount of vibration felt at particular speeds.
For the road rider that travels regularly at highway speeds, a “taller” gear ratio is often desired because it lowers engine speed at highway speeds and tends to reduce vibration. By swapping out the stock front sprocket (the countershaft sprocket) to one that is one gear tooth larger, the rider can expect engine speed to drop by 200-300 RPM, which can be more than enough to shift vibration away from common travel speeds, reduce noise and increase fuel economy.
A similar gear ratio change can be accomplished by swapping out the rear sprocket for one that is two-teeth smaller, but keep in mind that a smaller size sprocket creates a tighter radius for the chain (what’s known as “chain wrap”) which can contribute to more rapid chain wear. Making the change with a larger front countershaft sprocket is usually the preferred method as it will actually results in a larger chain wrap and reduced chain wear.
For a subtler gear ratio change, consider bumping up one tooth size on the front sprocket and down one tooth on the rear sprocket.
All together now …
Regardless of where you make the adjustment, front or rear or both, it’s a good idea to make the adjustment as a system. Replace both front and rear sprockets and the chain at the same time to assure even wear. High-quality components don’t have to be expensive. Check out the proven Sunstar chain and sprockets that are the choice of racers and manufacturers alike and available for your machine to maximize performance and reliability.
To learn more about selecting the right combination of sprockets for your bike, you may want to check out the handy sprocket combo ratios chart.
Have additional questions? Don’t hesitate to reach out to us directly to get the expert answers.