Noise and judder
Noises and juddering tend to be the most common and annoying issues that afflict the braking system. Grinding noises tend to be more serious and might point to brake linings that have worn out completely, promoting metal-to-metal contact. Comline’s Dr Keith Ellis, director of braking product development, told
CM: “Squeal is caused by vibrations that result from the interaction between a brake disc, brake caliper and brake pad, which tends to be influenced directly by various internal and external factors, including the temperature of the disc or pad, the ambient temperature in which they are operating, vehicle speed and the pressure level being exerted under braking.”
To resolve noise issues, anti-rattle shims may be fitted behind the brake pad, with some of these supplied with either new pad sets or fitting kits. However, Comline warns about the varying levels of quality and performance levels of these shims across the aftermarket and recommends you place your trust, investment and safety in a quality brake component manufacturer. Incorrect fitting/ lubrication can also increase noise – see Should you use copper grease? on page 8.
Many brake friction parts incorporate noise-reduction characteristics. Newer cars feature asymmetrical/directional brake pads, meaning that the friction material comes into contact with the disc at an angle, reducing noise and vibration. These pads might be identified by an arrow on their rear face, to denote the direction of disc rotation when the vehicle is moving forwards. Markings may denote if they need to be fitted to the left- or right-hand side of the vehicle – a half-moon cut-out in the moulded rubber anti-noise shim might also feature. Read installation instructions carefully. Driv/ferodo reports that fitting directional brake pads incorrectly is one of the most common issues that it encounters, prompting the company to upload an intructional video to Youtube: https://bit.ly/2xunh8w
While some suspension components are more prone to amplifying brake noise on newer cars, due mainly to their weightsaving construction, bear in mind that poor fitting can promote squeaks and judder. Take heed of these recommendations: 1. Do not use copper grease to lubricate shims. 2. Ensure that pads are located correctly, including referencing any alignment features. 3. Remove any corrosion from contact surfaces and the caliper bracket. 4. Use brake cleaner to clear the hub-to-disc surface and, if possible, check its run-out with a DTI gauge. 5. Check the new disc’s lateral run-out with a DTI gauge – it should not exceed 0.07mm below the maximum radius.