How Can I Keep My Disc Brakes From Squealing and Squeaking? [Quick Question]

The Quick Question series answers your MTB repair questions. Do you have a quick question about mountain bike repair? 🤔 Email [email protected] and we’ll do our best to answer it!

Noisy disc-brakes are atop the list of annoying issues for most mountain bikers. The squealing carried over from all forms of rim-brake technology and hasn’t been fully silenced since. This week’s techy repair query comes from a reader who truly can’t get their mountain bike brakes to S.T.F.U.. “Do your brakes squeal a lot after stream crossings? I feel like mine are louder, and keep squeaking longer than everyone I ride with. It doesn’t matter which brakes I’m running either: Shimano, SRAM, TRP, and others. Am I using my brakes wrong? Or should I be doing something to dry them out more quickly?”

The main aim of this series is to collect and share readers’ experiences and advice, and we hope you will contribute some helpful hints below. Over the past several years, I have only experienced the truly cacophonic howl of squealing pads and rotors with one set of brakes, for which I feel fortunate. We decided to crowdsource some initial answers to this time-honored conundrum by asking a host of professional riders and mechanics alike.

Brake Pad and rotor selection

Former DH pro and current adventure athlete, Amanda Batty, says that starting with a quality set of brakes and keeping them clean will help things considerably. “Invest in a good set from the get-go and keep them clean — fine-grit wet sandpaper and alcohol are your best friends for pads and rotors, but the better quality your brakes are at the outset, the more confidence you’ll have in being able to stop and control speed. The more confidence a rider has about stopping or controlling speed, the faster they’re able to ride.”

GT Factory Racing athletes Noga Korem and Wyn Masters both mentioned how pad compounds can make a meaningful difference. Noga said, “I am using Shimano XTR 4 pistons, with 180mm rotors and metal pads. For me they work the best.” Wyn echos this.

“Personally I like to use the metal pads with my Shimano XTR brakes, but occasionally I would swap to resin pads when it’s wet as I find a little more bite with them, just the pad life is much shorter.” 

Steve Blick from Specialized added a third vote for metal pads, and a hot tip on a pad alignment tool. “Historically, I use metal pads. Recently I have also been using this pad setting alignment tool.”

On to the rotor, there are stacks of discs that claim to reduce vibration and sound resonance. Dominik Voss from Magura said riders should “choose stiff rotors. Magura’s new MDR-P and MDR-C rotors have special stiffening elements that block resonances.” Voss also mentioned that larger rotors will dissipate heat faster, resulting in quieter brakes. Magura has a few install tips and tricks on their website that help to keep their calipers quiet.

Brake Caliper setup

Before aligning the calipers, it’s important to make certain that all of the pistons are pinching and contracting freely, adding equal amounts of pressure to the pad at the same time. Pro mechanic, Tyrone Dines, recommends folks “use a plastic or similar tool to re-set [retract] the pistons. It’s important NOT to use anything metal on the pistons, as often they are ceramic and quite fragile. Then squeeze the lever about 2 or 3mm and watch the pistons move. If one moves before the other, hold the moving one and squeeze the lever to unsettle the reluctant piston. [Then] you’ll see the caliper naturally align itself.”

Another prefunc step to aligning calipers is to have properly faced caliper mounts on the frame. Ben Hillsdon from Shimano says “Misaligned brakes can cause noise. If you don’t have flat frame/fork mounts then you’ll want to get your brake mounts faced to even out the alignment of the caliper. Then, centering pistons (p.64) is a step that’s often forgotten. Before installing the brake pads, the pistons have to be centered. This is done by installing a red pad spacer and pulling the brake lever a few times.”

Orbea Enduro Team rider Vid Persak also focuses on caliper alignment to reduce the squeal. “The best way to reduce the noise is to put two layers of metal (approximately 0.03mm) between pads and disc and press the levers. This will set the distance between them and reduce the noise. Make sure your pistons are centered because it can affect lever performance.” This tip works similarly to the pad alignment tool Blick mentioned above.

Initial bedding process

Almost every person who responded to our query mentioned bedding in the brake pads properly, to begin with. Chris Mandell from SRAM shared the above video to demonstrate bedding technique, and he also noted that riders will want to “avoid contamination from lubes, polish, and cleaners. and clean rotors when needed with isopropyl alcohol. [Additionally] don’t use automotive ‘brake cleaner’ as it can affect the seals adversely.”

Olympian Kate Courtney’s mechanic, Brad Copeland, has a good amount to say on the topic of pad and rotor mating. “I’d say this is one of the more neglected processes in bike setup and preparation but it is a recommended process from every manufacturer. Disc brakes always have a period at the beginning of their life where the brakes ‘get stronger’— this is in fact a product of further bedding-in of the pads/rotor, essentially a material transfer where some of the brake pad material embeds in the rotor surface and this gives the brakes more bite once the process has fully occurred; an initial cycle of medium-effort gradual stops will heat up the brakes, and begin the process of material exchange, coating the new brake rotor surface. In between these stops, I like to ride back up to speed with light brake drag to keep them hot. Do this a number of times. It can be quite an effort and take a while, but the results are immediately noticeable as the brakes gain power through this process. The pads also wear in a bit and develop a more perfect square contact with the rotor in the early days of their life, which further contributes to a solid contact feeling and usually less sound.”

Rotor and pad cleaning

Another prevailing theme in the tips we received from professional mechanics and athletes was to never touch the rotor or pad with your fingers, as the oil in your skin will contaminate the surface and cause the brakes to howl. Again, Brad Copeland has heaps of experience with delicate braking surfaces. “I learned early (and was lucky to usher in disc brake technology as a mechanic in a shop in the late 90s) not to even touch the rotor surface, lest I transfer some oil from my skin to the rotor. I’ve worked with pros [like] Jared Graves who asks to have his pads removed before cleaning his bike, and won’t continue to use pads that were installed on his bike in an environment where aerosolized bike cleaning products have been sprayed into the ambient atmosphere, even if we are outside under a tent. I’ve also had athletes lube their own brake rotors. Cycling is weird.” In case it’s not dead-clear, using any form of spray-lubricants to oil a chain is a sure-fire way to cause terrible brake noises.

Copeland goes on to describe methods similar to what Amanda Batty mentioned earlier around cleaning rotors and re-surfacing pads. “I recommend isopropyl alcohol (91% — the good stuff) on a lint-free rag and a thorough scrub of the rotor, in as much of the vents or grooves as possible, top edge, the carrier/spider — all of it. Be thorough. Do it twice if you really want to be safe. If you have some medium-grit sandpaper I like to remove the pads, and with the grit-side up, I place the sandpaper on my workbench and with the pad facing down make circles with the brake pad on the sandpaper to evenly take off any glazing that may have formed either from heat or from a period of disuse. I don’t go crazy but try to create an even “new” surface on the pad before reinstalling. I should state that I’d rather replace the pads altogether and start over fresh; however, this method works pretty well almost always.”

Finally, Vid Persak also takes care to remove the pads and rotors and clean them when washing the bike. “Also, an important thing is to always take out your pads and discs to wash your bike, especially with metal pads. This will help your brake pads get rid of the corrosion that might cost you noises and bad braking performance on the next ride.”

Once the pads and rotors are contaminated, they may be salvageable. Megan Rose, director of the Trans BC and Trans NZ enduro races, likes to heat things up a bit. “If they become corroded with an oil that shouldn’t have got on there, then I use a blow torch and burn the oil off the rotors and sand down the pads to try and get them clean and silent again.”

During all of that cleaning and checking, Robin from Hope Technology says to look for any leaks due to worn seals. “Check around the caliper for oil or worn out seals or bleed port and replace them if necessary.”

On-trail braking technique

While we only received a few replies regarding how to use the brakes, they are indeed useful points. Amanda Batty says, “on-trail braking is all about finesse: learn how to feather the brakes and short-stop to control your speed instead of ham-fisting them, and not only will your riding get better and faster, your brakes will last longer and require less maintenance!”

Singletracks contributor and full-time bike mechanic Sam James adds that “a lot of new cyclists don’t understand that noisy brakes in the rain is a fact of life. Some heavy braking will help heat the brakes up and evaporate the water off resulting in increased braking power and less noise. Though a couple of decent puddles and the brakes will be noisy again.”

Sam adds that at the bike shop, customers will often come in with glazed pads as result of dragging their brakes consistently. “One I find very frequently on customers’ bikes but is rarely mentioned is glazed pads. Dragging the brakes or improperly bedding them in will heat the pads up and glaze the surface to the point that they’re shiny and glassy. You can tell the pads are glazed because the braking surface on the pad is shiny and reflective rather than dull, and often the pad backing is discolored too from the [resulting] high heat. These are not ideal braking properties since brakes require friction to function properly. This results in poor braking performance and usually some squealing when just coming to a stop – rather than constant noise, like when they’re contaminated. To avoid glazed pads riders should concentrate on not dragging the brakes and [instead] braking late and heavily. To fix glazed pads, simply sanding the surface of the pads back and roughing up the rotor with sandpaper is all that’s required, and then a proper bedding in procedure – several hard stops from speed.”

Mixed tricks

EWS Pro Caro Gehrig has a unique nugget to share. “When changing brake pads, wet them with water and rub them against each other before the first use. This helps the organic pads to break in better.

Finally, Copeland had a few ringers to add in case nothing else is working. “You might have noticed on copper paste-type, anti-seize compound tubs, there is often some iconography related to automotive (car) disk brakes on the label. It is pretty common to apply this compound to the backing plates of brake pads on cars in the area where they contact the caliper piston, which among other things helps reduce harmonic vibration in braking moments and thus reduces squeal. Well, guess what—this can be done on bikes as well, with the same result, but just take care not to get any of the anti-seize on the rotor or pad surface. It’s a thick and resilient grease-type substance that can change or prevent the harmonic vibration effect of braking by acting as sort of a damping agent against the high-frequency pad vibrations. 

“Some other voodoo methods include mixing pad compounds (resin and metallic, in other words) to reduce or alter the harmonics or high-frequency pad vibration under braking. This might work some of the time, but the jury is kind of out on that technique. I might save this for the last Hail Mary if all other bets are off. There are also some brake systems, or rotor types, that are notoriously noisy, and sometimes there is only so much you can do!

“Oh here’s another one — you really should not mix rotors that have been bedded in with resin pads with metallic pads should you choose to switch compounds; rather, you should replace and track which pads were used on your rotors, and keep them all together. Because of the material transfer mentioned earlier, it can create weird or ineffective bedding with the new pad material that can limit maximum possible braking power, and also contribute to noises and squealing sometimes.”

Finally, my good friend and fellow journalist with Wideopen Magazine, Pete Scullion, had a comedic approach to the issue. “I think my brakes would make less noise if I live somewhere that wasn’t as wet as a mermaid’s flip flop. Top tip: don’t live in Scotland if you want quiet brakes.”

To sum all of that up, buy quality gear to begin with, some rotor designs will resonate less than others, consider picking up some pad alignment and rotor truing tools, make sure that the pistons are moving equally, check that the frame and fork mounts are properly faced, align the caliper evenly, bed the pads in before the first ride, keep the rotors and pads clean and away from spray lubes and cleaners, never use aerosol chain lube, don’t touch the braking surfaces with your skin, don’t drag your brakes unnecessarily while riding, try wetting organic pads and rubbing them together when new, maybe try anti-seize compound between the piston and pad backing, and don’t mix rotors that have been used with compounds other than what’s currently in your caliper. Oh, and don’t ride places that are wet as a mermaid’s flip flop.

We would like to thank the above contributors for sharing their helpful tips. What’s your solution to silencing disc brake squeal?

The Quick Question series answers your MTB repair questions. Do you have a quick question about mountain bike repair? 🤔 Email [email protected] and we’ll do our best to answer it!