What Rear Sprocket Size Should You Choose for Supermoto Conversion?

What Rear Sprocket Size Should You Choose for Supermoto Conversion?

Feb 15th 2014

This question is hands down the most commonly asked and the most complex to answer. But, here goes!

Let’s start with the concept of gearing ratios. The gearing ratio determines how the engine RPM is translated into the rear wheel speed of the bike. Changing your sprocket sizes (front, rear, or both) changes the ratio and how your bike puts the power to the ground.

A simple calculation will give you your bike’s gearing ratio. If the stock sprockets on your bike are 13 teeth on the front and 50 teeth on the rear, then your gearing ratio is 3.846 (50/13).

You can use this as your baseline to work with. If you drop to a 44T (the most common Supermoto conversion sprocket tooth size) your ratio is now 3.385 (44/13). You have more top speed this way and less “bottom end” acceleration. 44T is followed by 42T as the most common SM conversion options.

You will lose some bottom end “acceleration” when dropping teeth but since you’re on the street now and need more top speed for highway riding, you’re better off losing a little on the bottom end to gain the top speed. This will keep the bike from revving to high and “topping” out earlier than you may prefer. If you want to get real “tech-y” with it, we have an awesome resource we like to use. Just click the link here: https://www.gearingcommander.com

So put simply:

  • Larger front sprocket/smaller rear sprocket = higher top speed/less acceleration
  • Smaller front sprocket/larger rear sprocket = lower top speed/more acceleration

The choice is yours as to whether you change the front or rear sprocket or both. Warp 9 wheels come with a new rear sprocket, so an easy option is to just do your adjustment there and order a smaller tooth than your stock. If you do want a front sprocket, we have those for sale here. In most situations, you really may need to ride the bike with your new sprocket and decide if you need to make any adjustments from there since so many factors come into play. Keep in mind, it’s not that dire of a decision. If you are in doubt, go with the 44T. If you think you want more top end, go 42T; or more bottom-end acceleration go 45 or 47. Wanna just ride wheelies all day? Go big and do a 50 or 52T! It really is dependent on your riding style and needs. 

If you're still in doubt and want help, that's what we're here for! Call, text, or email us and our friendly staff will be happy to answer your questions, or just chat about how cool riding your dirt bike on the street is :)