What is a Bicycle Clutch Derailleur? – The Ultimate Guide

Zoom on a bicycle clutch, chain and chainring

A bicycle derailleur clutch is a mechanical system that keeps the chain under tension during the ride, so it loosens less and stays in a better position.

As a huge bike enthusiast, I researched for you the important information about bicycle clutches and condensed everything in this article.

Let’s get started.

What is a bicycle clutch?

Bike clutch opened
Photo from Smartpapercup

A bicycle clutch is a system that is part of the rear wheel derailleur, it is mainly composed of a pivot axle around which the derailleur turns and a metal ring (friction band) surrounding the axle. When the clutch system is engaged, a cam-shaped piece applies pressure on the ring resulting in a tightening of the axle. The rotation of the derailleur is then more difficult because of the tightening of this ring, which then tends to increase the tension of the bike chain.

What does a clutch on a bike derailleur do?

As I explained to you, the clutch of a bicycle restrains the rotational movement of the rear derailleur, thus the clutch:

  • Increases the chain tension considerably
  • Prevents the chain from bouncing and dropping
  • Prevents the chain from slapping the chainstay and making horrible noises
  • Helps the bike chain to stay on the chainring (especially if the bike has no chain guide)

Overall, a bike clutch minimizes the bad movements of the chain.

What is bike chain slap?

Chain slap is a problem that many people know, have encountered or will encounter. When you ride on particularly rough roads, go downhill — in short, when you abuse your bike — the chain will have a vertical movement due to the shocks. If there is too much slack in the chain, it will hit the chainstay every time, causing a distinct noise and damaging the frame.

To avoid ruining your chain and the chainstay, you need to fix this problem.

Some bikes are directly equipped with protections on their chainstay, others are not. If this is not the case, some riders will make a makeshift protection with a piece of inner tube while others will buy a real protection.

How do I adjust my bicycle clutch?

It can happen that you have a bike with a clutch mechanism but it is not properly adjusted. Indeed, we can often think that the bike store has taken care of all the adjustments and that we don’t need to do anything but get on the bike and ride. The reality is quite different, often the clutch is too loose after the purchase or worse, it may simply be off.

Adjusting your bike clutch is therefore very important and guess what: it’s easy to do.

Zoom on a bike derailleur
New clutches allow adjustment from the outside

While the first models required the removal of their cover to adjust them, the recent clutches allow direct access to the adjustment bolt from the outside. You just have to take a key and screw or unscrew it according to the desired adjustment.

Do clutch rear derailleurs add drivetrain friction?

Theoretically no. The clutches only work in one direction and therefore do not cause friction when you stop pedaling for example.

However, tests have been done on Sram and Shimano models and it seems that Shimano clutches add a very slight friction due to a play in the derailleur.

So, depending on the model, a rear clutch mechanism could have a slight impact on the performance, but it’s hard to say with precision. It is possible to go for an ideal derailleur configuration: a light derailleur spring and a heavy clutch force.

Clutch derailleur VS No Clutch derailleur: what’s the difference?

Here is a very interesting video on this difference:

Do all bikes have a clutch?

No. In fact, the first clutches appeared thanks to the Shimano brand in 2011, if today this system is well democratized in the world of mountain biking, it is less common to see it equipped on road bikes or low-end bikes.

What is next?

Now that you know everything about how a bicycle clutch works, if you are a mountain bike enthusiast, you might want to consider adding a few dollars to your next derailleur purchase to get a model that contains a clutch.

With this, no more worries about the chain dropping or not, it’s efficient and that’s all we ask.

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