Brake squeal is an annoying and sometimes costly outcome of servicing a vehicles braking system. Brake specialist Brembo has issued some advice on strategies to avoid this and ensure optimum braking performance.

1) The discs - Always evaluate both the disc condition and its thickness. Minimum thickness is generally marked on the rim of the braking surface or on the hub surface. Discs should be replaced if they are below minimum thickness because they will not be able to dissipate heat correctly. Brembo advises against turning or grounding the braking surface. The technician should also check the discs per axle at each change of pads for grooves and cracks.
Discs should be cleaned, with a suitable cleaner, including cleaning the braking surface (unless the disc is coated) and the surface that comes into contact with the hub. The anticorrosion layer must be completely removed.

2) The hubs – The surface of the hub should be cleaned before installing a new disc. A variety of options, which include a hub resurfacing tool, a wire brush and spirits can be used to eliminate rust and other deposits which can lead to disc runout.

3)Check for runout – The technician should always measure the disc before and after maintenance, using an appropriate tool to ensure that runout does not exceed 0.10mm when the disc is fitted, as runout variation is a common cause of brake vibration. Tighten the disc using wheel screws and washers to simulate the thickness of the wheel.

4) The pads – pads should be checked for thickness and surface and replaced if necessary. Pads that are below specifications can result in safety and noise issues like cracking and fading. When fitting the pads inside the caliper body, ensure they are being installed in the correct direction, which can be indicated by the presence of arrows, the letters ‘L’ (left) and ‘R’ (right), a crescent or half-moon cut-out on the anti-noise shim, or differentiated chamfers on the pads themselves. Fitting the brake pads on the wrong side can lead to unwanted noise.

5) Seal and sliding element -  Clean and lubricate caliper slide pins, pin boots  and external piston seal. Check pistons, seals, boots and sliding elements on the caliper to ensure that they are free from damage and corrosion and able to slide. Use specific grease suitable for each component and replace if needed

6) Torque - Failure to use a calibrated torque wrench on all brake components and wheels in a star pattern can result in brake groan and pedal pulsation, potentially causing disc damage. Check vehicle data for the correct torque.

7) 300km ‘bedding-in’ period - After any braking replacements, every mechanic should carry out a road test themselves and then advise the driver to ‘bed-in’ their new system for around 300 km. This means that the driver must avoid abrupt and intense braking. The driver must also look out for vibrations and noise coming from the brakes, both when driving and braking. This is a vital aspect in ensuring that the discs and pads align correctly.