Sprockets

Along for the Ride - All you Need to Know about Rear Sprockets

It’s easy to think of your motorcycle’s sprockets as a pair. Yet, they play very different roles and are subject to different stresses. The main difference between the front and rear sprockets is that the front is driven and is directly attached to the gearbox output shaft. Meanwhile, the rear sprocket owes its movement to the chain. The front sprocket attached to the gearbox shaft has little movement other than regular rotation. The rear sprocket is approximately half a meter away and connected via a chain. Any play in the chain accelerates wear, which is why the rear sprocket wears faster than the front.

Steel Rear Sprocket

Various grades of carbon steel are the most common material used for rear sprockets. Although this is the heaviest option, it is also the most cost-effective. Carbon steel also offers a good compromise between strength and durability. Also, it is easy to machine.

Aluminium Rear Sprocket

If you want to rid your motorcycle of every gram of excess weight, an aluminium rear sprocket is the way to go. These types of sprockets are well over 50% lighter than steel. The downside is a slightly faster wear rate. However, top-shelf aircraft-grade aluminium such as 7075 T6 is almost as hard-wearing as steel.

Combination Rear Sprocket

The combo sprocket, more often known as a twinring or interlink, is a rear sprocket comprised of two pieces. The outer toothed element is steel. The inner carrier is aluminium. This type of rear sprocket offers a great combination of steel teeth for durability, with the aluminium inner ring offering impressive weight-saving.

Inspecting for Wear

As the rear sprocket is exposed, it’s possible to carry out regular inspections. Regardless of the sprocket’s composition, wear patterns tend to be the same. Signs to look out for include pointed, sharp or hooked teeth and in extreme cases, chipped teeth. Any of these signs of wear mean it’s time to buy a new sprocket and depending on the severity, maybe a new chain. Take care when adjusting the drive chain. A misaligned chain will cause a considerable acceleration of sprocket wear.

Adding Teeth to the Rear Sprocket

Increasing the size of the rear sprocket by three or four teeth will provide faster acceleration and more rapid throttle response. It will, however, lower your top speed and increase the frequency of gear changes. While this may have limited use on the road, altering the gearing is beneficial and cost-effective for track day riders. The final consideration to adding more teeth to the rear sprocket is the likelihood of needing a longer chain.

Reducing Teeth on the Rear Sprocket

Dropping down three or four teeth will have the opposite effect: slower acceleration and a higher top speed. When changing to a smaller rear sprocket, if the drive chain is in good enough condition to keep, you may have to remove a link to reduce the length.