Why brakes squeal

By Christian Jensen - 26.04.2026

You’re flying down the mountainside and heading into an off‑camber turn. You grab the brakes, and they scream like two stabbed pigs. A bit startled, you squeeze harder and come to a stop. Your first reaction is to look around; did anyone hear that awful noise? Then the troubleshooting begins. What on earth just happened?

Half‑nervous, you start pedaling again and test the brakes once you pick up some speed. Sure enough, they howl again. So what’s causing it?

The answer depends partly on whether you’re running metallic pads or resin pads. Most riders choose resin these days, they’ve become more durable and are far quieter. Metallic pads are typically used in wet and dusty conditions, which means they’re actually perfect for Norwegian riding. They also last longer than resin pads. The downside? Metallic pads tend to squeal more often and more loudly. If you want silence, resin is the way to go.

Regardless of pad type, contamination between the rotor and the pads is usually the culprit. Dust, mud, water or maybe a ride through a pine forest where you picked up some pollen, can all cause noise. In most cases, a proper cleaning is all you need.

If you inspect your rotors and they still look dirty even after washing, you might notice brownish streaks, as if someone held a marker against the rotor while it spun. The rotor on the right in the photo below has a clear stripe and several faint ones. That’s a sign you’ve gotten something oily on both the rotor and the pads.

To get to the bottom of it, you’ll need to remove the brake pads as well. They’re usually held in place by a small retaining pin. Depending on your brake model, you pull the pad pair up or down. Even if the pads aren’t heavily worn, they may still be due for replacement.

When I pulled the pads from my bike, they looked soaked in old oil. No wonder the brakes were screaming.

One more thing worth checking: clean the entire caliper thoroughly so you can see whether the oil came from a worn seal inside the caliper itself. In other words, you might be dealing with leaking brake fluid.

Pads contaminated with oil should simply be thrown away. The oil soaks into the pad material and the noise will never stop. Brake cleaner costs more than a new set of pads anyway, and the waste from cleaning is worse for the environment than replacing the pads.

But what about the rotor? I’ve managed to save quite a few rotors with a simple trick. First, I degrease them with a basic degreaser. Nothing fancy, cheap stuff works great. I scrub the rotors with a cloth, wipe off the excess, and spray on regular dish soap. After a quick rinse, I grab 600‑grit sandpaper. With the rotor still wet, I sand around the braking surface where the pad marks are visible. Try to sand evenly across the whole rotor. I usually follow the rotor pattern and do ten strokes per section before rotating. I repeat this until the rotor looks clean and shiny again. Once the worst brown streaks are gone, most of the oil should be gone too.

Finally, I degrease and wash the rotor one more time with dish soap to remove any particles loosened during sanding.

Quick summary

If your brakes are screaming, start with a proper cleaning. If you see discoloration on the rotors, it likely came from the pads. Remove the pads and inspect them. If they’re discolored or oily, replace them and clean the rotors. Before installing new pads, wipe down the caliper area thoroughly. There may be brake fluid leaking out and contaminating your pads.