June 26, 2019

Words by Richard Roberts

Looking after your disc brakes and avoiding the howl

Working in the bike shop, one of the questions we get asked most frequently is:

“why are my disc brakes sooooo noisy?”

Here I’m going to try and explain how to take care of them and why they can become real howlers. Disc brakes on bikes are a relatively new phenomenon to a lot of people. They have been common on mountain bikes for two decades, but recently have become prevalent on road bikes too.

There are a few things that are helpful to know to keep your disc brakes working quietly and effectively. Like all brakes, disc brakes rely on friction to stop you. In this case, small brake pads are located in a caliper on the frame and fork, near the centre of the wheel, and these bite onto a rotor in order to slow you down. The pads on a disc brake are composed of a metal backing plate onto which is bonded a 2-3mm thick softer, heat resistant, braking material. Over time, as you brake, this softer material wears away.

If your disc brakes make a horrible, metallic, grinding sound when you brake, the likelihood is that you have worn away the braking material and are down to the backing plate. Do not ride your bike like this. Your brakes will not work safely and you will very likely damage all the components in your braking system.

The best thing to do is to occasionally check the amount of braking material left on your pads. As a rule of thumb, if it is down to 1mm then it is time for new pads. Pads are relatively cheap (from £10-25 depending on your brake).

Replacing them before they are completely worn out you will prolong not only your own life, but that of your brake components too.

If you brake with a very worn pad you can often end up wearing away the rotor (the metal disc at the centre of your wheel). In extreme cases of wear these rotors can fail with obvious dangerous results. Again, rotors can be replaced relatively cheaply if they have become worn.

Glazed pads

Quite often, long before pads are worn down to their safe limits, disc brakes can lose their power and start to make horrible squealing noises. This usually occurs because the disc brake pads have become contaminated. The braking surfaces of the pads and rotors pick up oil and grease from road surfaces, from overspray of bike lubricants, or, sometimes because hydraulic fluid has leaked from the braking system. This leads to the pads and rotors getting polished and becoming glazed – so losing the friction that they require in order to stop you effectively.

When this occurs it is sometimes possible to take the pads out of the brake caliper and roughen them up with a file or sandpaper in order to remove the glaze. Likewise, rotors can be cleaned and lightly sanded to restore friction.

Here are a few basic tips to keep your brakes running quietly and safe:

  • Clean your disc brake rotors regularly, especially if the weather is wet. Road and trail grime can build up on your rotors and are transmitted to your pads leading to them becoming glazed. Use a specific disc brake cleaner such as Fenwicks. Spray this onto the disc rotors, leave it for a few seconds and rub thoroughly on both sides of the rotor with a clean rag. This is a job that need only take 5 minutes if done regularly and will keep you stopping well and prolong the life of your pads and rotors.
  • NEVER EVER spray your disc brake caliper or rotor with oil or any other lubricant. With the exception of the chain, components on modern bikes do not need spraying with oil – and even the chain only needs the smallest amount of oil on its central rollers for it to work optimally. Oil on the pads and rotor will quickly lead to loss of braking power and horrible noises.
  • Try and check your pads for wear. You can often judge this by looking down through the brake caliper. Better still, take the wheel out and inspect them this way. According to how much you use your bike, the terrain you ride on, your speed and the weight of you and your bike pad life can vary tremendously. Manufacturers say to check them before every ride. In the real world check them perhaps every couple weeks.

All the above tips are simple and we are happy to show you what you need to do. A tiny bit of regular attention will save you money in the long run and will keep you safe on your bike and hopefully howl free.