The Relationship Of Clutch Derailleurs and Oval Chainrings Analyzed

Description of the Concern

A clutch derailleur comes with a mechanism (clutch) that prevents the cage of the derailleur from moving excessively during extreme riding.

The objective of the clutch is to ensure consistent chain tension regardless of the terrain while minimizing the chain’s up and down movement.

Combining a clutch derailleur with an oval chainring creates a possible conflict.

An oval chainring has a varying radius resulting in small chain tension variations during each pedal stroke.

In consequence, the chain pulls the derailleur’s cage every so slightly forward during every crank revolution.

Some cyclists say that those small movements wear down the derailleur’s clutch.

Is The Effect of Oval Chainrings On Clutch Derailleurs That Strong?

Oval chainrings are undeniably pulling the chain during every revolution of the cranks.

The motion may be minimal, but on a long ride the number of pulls gets very high and damages the mech through consistency rather than force.

However, it would be wrong to conclude that oval chainrings aren’t compatible with clutch derailleurs.

A quality derailleur should be able to sustain the stress caused by an oval chainring.

It’s also worth mentioning that other factors could stress the derailleur much more than an oval chainring.

Those would be:

1. Full-suspension frame

The rear triangle of a full suspension bicycle is constantly moving up and down according to the terrain. The movement places a lot of stress on the derailleur because the chain shortens and elongates.

2. Shifting

During every shift, the cage of the derailleur assumes a new position to maintain high chain tension. The result is stress on the derailleur and its clutch.

3. Vibrations

When riding on uneven terrain, the chain is bouncing up and down. It’s up to the derailleur to “calm it” down.

4. Extreme Chain Lines

The popular 1x drivetrains cause inevitable cross-chaining when riding in the smallest gear. The extreme position of the chain places extra demand on the derailleur.

Minimizing The Negative Effect of an Oval Chainring On a Clutch Derailleur

The following steps can be taken to slow down the wear of the clutch:

1. A quality chainring

A properly shaped oval chainring ensures that the same number of teeth are engaged during every part of the pedal stroke. This design reduces the chain tension alterations to a minimum.

2. Properly pre-set chain tension

The general rule of thumb for pre-setting a bike’s chain tension is to have 1/2″ (1.27cm) of up and down play at the tightest spot.

On a geared bike with a derailleur, this is achieved by shortening the chain to a proper length. You can read how that’s done in this article.

If the chain is too short, it will have a greater pulling effect on the derailleur.

3. Respect the derailleur’s capacity

Combining a large cassette with derailleurs that aren’t designed for such operation stresses the mech and causes poor shifting.

4. Routine servicing of the clutch

Modern derailleurs are pretty tough and can sustain a lot of abuse.

Eventually, however, even high-end models fatigue and require servicing which includes disassembly, degreasing, and re-greasing.

If you have “chronic problems” with the clutch on your derailleur, chances are that they will disappear after a maintenance session.

For information on how to service a clutch, consider reading this article.

Note: Derailleur clutches need servicing even if you aren’t using an oval chairing because the mechanism gets dirty and dry over time regardless of the drive train.

For that reason, many riders service their clutch once or twice during a season depending on the frequency and intensity of riding.

What Are The Signs of a Clutch In a Poor State

1. Annoying Rhythmic Squeaking

Annoying squeaking matching the pedaling rhythm of the rider is the most common symptom of a derailleur clutch in need of servicing due to prolong riding with an oval chainring.

2. Rough Movement of the Arm With the Clutch On

If it takes a lot of effort to move the derailleur’s arm, and its motion isn’t smooth when the clutch is engaged, then the clutch requires servicing.

3. Smooth Operation With a Disengaged Clutch

Another sign of a worn clutch is the absence of squeaking and abrupt movement when the clutch is disengaged.

4. Poor Shifting Performance

A beaten derailleur clutch can cause degraded shifting performance.

Will The Clutch Wear Prematurely If I Use an Oval Chairing?

Oval chainrings cause back and forth oscillation of the derailleur arm.

However, if the derailleur and the chairing are of good quality, the system should last years, especially with proper servicing.

Note: It’s hard to determine whether the clutch’s wear is caused solely by the oval chainring. The terrain and the riding style of the rider greatly impact the system.

Will A Classic Round Chainring Minimize Clutch Wear?

A round chainring has the same diameter at all points and doesn’t create alternating chain tension.

Therefore, technically speaking, a round chainring places less stress on the clutch. If increasing the clutch’s lifespan is a priority, a round chairing is a better choice.

Summary: What You Need To Know

1. The irregular radius of oval chainrings results in varying chain tension.

In consequence, the chainring pulls the derailleur ever so slightly during each pedal stroke.

2. The clutches of some derailleurs develop a squeaking sound over time when combined with an oval chainring.

There’s anecdotal evidence that Shimano derailleurs report similar symptoms more often than SRAM’s models.

3. Other factors (e.g., terrain, bike geometry, drivetrain properties…etc.) contribute to the degrading performance of a clutch mechanism.

4. Proper servicing of the clutch keeps the derailleur’s performance sharp in the long run.

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