How to Stop Bicycle Disc Brakes From Squeaking

Most disc brake users have had issues with squeaking brakes. So, today we are going to look at how to stop bicycle disc brakes from squeaking, why it happens and what to do about it.

Why do the disc brakes squeak?

Contamination. This happens when brake pads and the disc rotors get in contact with oil or other lubricants. Once the pads absorb the contaminant, they lose their braking power and can develop a squealing noise.   

Incorrect bedding in. “Bedding in” is a process which transfers braking material from the pads onto the rotor to create a layer that improves braking power. Missing this procedure may glaze the pads or transfer an uneven layer of the pad material that is burned in the rotor surface. This may cause noise, vibration, and low braking power.

Even layer of transferred braking material
Uneven layer of transferred braking material

Worn pads. When disc brake pads have worn through all of their friction material, the metal backing of the pad rubs on the metal rotor. This causes a loud squeaking noise and will damage the rotor. 

How to stop bicycle disc brakes from squeaking

There are a number of theories behind how to stop bicycle disc brakes from squeaking 

Cleaning disc rotors and pads using isopropyl alcohol or disc brake cleaner.  

Isopropyl alcohol is great for removing the grease and oil from the disc rotor without leaving behind any residue. However, if an uneven pad transfer layer has burned into the rotor surface, then cleaning the disc will make no difference as the vibration has literally been baked into the rotor.

Cleaning the pads will definitely remove contamination from the surface of the pads and make them look nicer but it will not solve the noise and braking power issue as the lubricants soak into the pads rather than staying on the surface.

Sanding the pads and the rotor

Another way to get rid of contamination is to sand the layer of the brake pad material. This may only work if you spot the contamination right away and act fast or if the pads have been glazed. 

Cooking the pads

In theory heat can burn contaminants from the braking material. However, as the material is porous and it absorbs lubricants it will be difficult to remove all the oil from inside the pads, meaning that they will never work efficiently. Also, the heat may weaken the bond between the brake pad surface and backing plate.

How to stop bicycle disc brakes from squeaking if these methods don’t work?

If you have enough commitment to try these options and your brakes still squeal, then replacing the pads and rotor will be the answer you were waiting for all along. For the price of the pads and rotor it’s worth using this option. 

When you remove old pads from a hydraulic disc brake, check to see if there are any oily marks on the back of the plates or corrosion on the caliper. This means that there’s a leak somewhere in the brake caliper and more likely the brake fluid will find its way again to reach the rotor and pads. If this is the case then replacing the pads and rotor will not solve the problem.

Oily marks on the back of the disc pads plates
Corrosion on the caliper.

Don’t forget to bed the pads in before you use new brake pads and rotors. To bed in the pads, first ride your bike on a flat surface at a moderate speed.

Press the brake lever gently until you slow down to a walking speed.

Use only one brake at a time. Repeat the process twenty times on each lever. 

A note on Contamination. This is normally in the form of oil and grease.  Because the pads are made of metal, the contaminant embeds in the braking surface and makes it virtually impossible to remove. Unfortunately, the contamination passes between the pads and the rotor, so the pads and rotor will need to be changed or clean.

It’s best to have new pads to ensure that there is no contamination still on the pads.  The rotor needs to be thoroughly cleaned with isopropyl alcohol, including all the gaps and holes.  Because it is so hard to clean, and any residue of contaminant will transfer to the new pads, the best practice is to fit a new rotor as well as pads.

Hopefully you now to know to stop bicycle disc brakes from squeaking. If you are more of a visual learner, our video might help:

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