Brake Noise

Brake noise or squeal is a vehicle system problem since the severity, regularity and tone is a function of the brake and suspension components in combination. This does not represent a problem on competition vehicles where performance is the primary objective but is generally unacceptable for road use. Some vehicles are particularly susceptible to the problem.

The contact between the pad and disc during braking creates the raw energy to produce the noise but the actual squeal can be primarily or a combination of the disc, caliper and pad. Elimination of squeal under all brake operating conditions is difficult to achieve when specifying a brake package whose purpose is to safely absorb very high energy inputs. A number of methods are available to reduce the noise factor of a brake system but assuming the base vehicle suspension system is settled, the reduction or elimination of noise is usually achieved by a process of trial and error. The first and easiest solution to try is the addition of high temperature grease to the back of the pad to provide a damping medium between the piston and pad.
Typically Copper Slip is applied although care must be taken to avoid any grease coming into contact with the pad face.
The use of high friction brake pads such as Pagid RS4-2 / M1177 creates high energy at the friction interface which can characteristically lead to more brake squeal but some pads are typical for their lower noise rating. These pads are characterised by their lower friction coefficient and reduced initial ‘bite’.
Examples of such a materials is Ferodo 3432F. There are a number of disc variants available from AP Racing and the type chosen can have an effect on brake noise, depending again on the pad choice. Generally it is found the multi drilled or grooved discs used in conjunction with competition pads will give unacceptable noise levels for road use, Plain face discs can cause higher levels of squeal, as the pad is not cleaned by the actions of holes or grooves. For the AP Racing Formula Big Brake it conversions, we have found a reduced drill pattern with a radiused edge and using Ferodo DS2500 pads give little or no pad noise and still have good performance. Where the noise is a function of the brake pad temperature, characterised by the noise reducing (possibly to zero) as the brakes are used more severely. The pad may also respond to the addition of pad chamfers which reduce the effective pad area and change the pad shape / centre of pressure. These chamfers (10,0mm x 30 degrees) can be added to the leading edge first and their effect assessed prior to the addition of a chamfer on the trailing edge.
Please contact AP Racing technical section for details of availability and specific requirements.