Brake noise is generally caused by vibrations of a part within the wheel end section of a car, i.e. between the chassis connection and the tyre. These noises are typically blamed on the brakes, however it can come from any part. Your brake system will always have some vibration, but this wouldn’t normally be strong enough to produce an audible sound.
Low frequency vibrations – Judder
A judder is a deep noise caused by a frequency below 300Hz.
Improper fitment of the hub or excessive disc thickness variation could result in poor tolerance, which could produce a judder noise. Damaged brake discs could also be a cause, in this case it’s best to get brake discs checked out by a professional.
To combat this, you could replace your brake disc, and clean and lubricate all surfaces of the brake assembly. Please follow your vehicle manufacturer’s guidelines.
Medium frequency vibrations – Squeal
A squeal is a noise with a frequency ranging from 300 – 5000Hz.
A squeal might likely be caused by a sticky movement on the caliper piston, non-planarity of the disc working surface, pad fitting errors, incorrect anti-noise fixing allocation and low disc thickness.
You will want to clean and lubricate components of the caliper, and make sure that the disc planarity will remain with a tolerance of 0.1mm. Now clean the surface of the hub, machine disc surface, and replace the disc, making sure that the brake pads, shims and accessories are fitted properly.
High frequency vibrations – Squeak
A squeak is a noise caused by a frequency above 5kHz.
A molecular vibration in the friction material during application to the brake disc is the most common cause of a squeaking noise.
You can remedy this by replacing the brake pad set. You would also be wise to make sure that all the accessories are correct and fitted properly.