Diagnosing and Rectifying Brake Noise

One of the most common complaints that drivers have when it comes to their brakes is excessive noise, and it’s one of the main reasons that vehicles end up in the workshop. Understandably, excessive noise during braking causes considerable angst for motorists who are accustomed to modern, quiet vehicles.

At its most basic, brake noise occurs as a result of the pads contacting the rotor or drum under braking application, but the root source of the noise can be far more complex, with many associated braking components all coming into play.

When diagnosing the cause of brake noise, in a disc brake set-up, it’s important to check that the caliper slides are free to move and not inhibited by any binding or seizing. A seized slide pin can cause several issues including uneven brake wear and drag along with noise. If the slide pins are seized or dry, they should be thoroughly cleaned and lubricated using Bendix Ceramasil or other suitable lubricant.

Properly lubricating brake caliper components can help minimse brake noise.

The condition of brake shims are also important to help keep noise in check. Attached to the friction pad backing, brake shims provide a barrier between the brake pad and the caliper, helping to prevent small vibrations, which build into noise. As with the slide pins, shims should also be properly lubricated – a light coating of Ceramasil between the shim and the backplate of the brake pad will better assist damping.

While it’s not necessary to renew all braking components when brake pads are replaced because of different lifecycles and wear rates, all brake parts should nonetheless be given a thorough inspection to pick-up any potential issues.

In the case of disc brake rotors, the disc brake surface should have a uniform wear pattern (light grooves are normal) with no scoring, excessive scoring can also promote brake noise as this excites the brake pad vibration.

If rotors surfaces are showing ribs, they can be machined (provided they remain within the required thickness tolerances) to make them smooth and eliminate another possible case of brake noise.

During pad installation the technician should check that pads fit into the caliper properly, abutting firmly but not bind. If it’s a loose fit, this could indicate some wear or distortion at the abutment clip area. If this is the case, any defective parts need to be remediated, as issues in this area can be a source of vibration that ultimately lead to noise.

Additionally, a small amount of Ceramasil lubricant or high temperature lubricant should be applied to the abutments (at the end of the pads that contact the caliper clip), to make sure the pads are free to move during normal operation.

Pads that don't properly fit the caliper will also cause excessive noise when the brakes are applied.

With some aftermarket brake pads, it can be common for noise to occur during the bedding-in phase while the brakes are making 100 percent contact with the rotor. This can take around 100 stops to subside. For Bendix pads with Titanium Stripe Technology, bedding-in isn’t needed because the friction material is formulated to rapidly mate with the rotor when brakes are first applied, and full braking performance is achieved instantly.

There are some other circumstances where brake noise can arise temporarily. If a vehicle is left outside for extended periods without use or in high humidity environments, a buildup of surface rust on rotors can occur, but this should quickly resolve itself as the brakes are applied throughout the journey.

If vehicles are left outside for extended periods surface rust can form on the rotors, temporarily causing noise when the brakes are applied.

If noisy brakes do arise from one of the other causes, for most drivers this can be rectified at the hands of a trained braking specialist or mechanic, but it still pays to understand the complexities of the braking system and what’s involved in sorting out the issue.

For further information:

For more information free call the Bendix Brake Advice Centre on 1800 819 666 or +61 3 5327 0211 from overseas (8am-5pm Monday to Friday EST), e-mail us at: brakeadvicecentre@bendix.com.au or visit our website www.bendix.com.au