BRAKE PAD SQUEAL AND OTHER NOISE PROBLEMS
Basically the noises heard from the brake systems (assuming that the pads are not simply
worn out) are dividable into two types of noise.
A GRINDING SOUND and BREAK SQUEAL. Brake squeal is a common problem and is the
nightmare of all pad manufacturers. It is caused when the pad “bounces” in a calliper and the
squeal noise is resonance between the back plate and the piston.
The grinding noise that is sometimes heard (more frequently with semi metallic not Asbestos
pads) is somewhat unnerving and sometimes tends to sound as though the pads are
completely worn out.
The third noise, which can come from the brake system, is after the fitting of grooved or
drilled brake rotors, which can be a whirring or aeroplane type sound.
We have found that the fixes for all of these problems are as follows;
Applying plastic shims to the rear of the pad can dampen this, but these are expensive and
to fit them on every pad where the incidence of brake squeal can be only 1 in 10 is false
economy. These are however, available, as a low cost accessory item.
We definitely do not recommend the use of general workshop greases, especially Coppaslip
on the back of brake pads as these are a friction reducing agent being applied in the area of
the only part of your vehicle which is designed to produce friction – the brakes. There are,
however, some “paint on” anti squeal silicone/rubber based materials, which are viscous
enough to stay where they are placed and are useful in reducing brake squeal.
On certain BMW and Audi calliper fitments, we have found that applying a 5mm or 1⁄4 inch
chamfer at the front and back leading edges of the pad has the effect of completely reducing
the squeal. (Many OE pads ARE chamfered in this way). This is a fix, which needs to be
done by a knowledgeable workshop mechanic if the problem arises, but the measurements
above should not be exceeded. As our pads are TOTALLY ASBESTOS FREE, there is no
health hazard with the dust generated and a competent mechanic can use a belt sander,
bearing in mind our dimensions mentioned above are maximums and a normal dust mask is
advisable.
One of the MOST PROMINENT REASONS causing brake squeal on used cars is poor disc
condition. Pads will often make a noise due to vibration whilst bedding in. The worse the
condition of the disc obviously the longer it takes to bed in and the longer the noise
continues. Pads that have not achieved a 90% SURFACE AREA CONTACT with the disc
will ALWAYS squeal.
We have seen plenty of examples where pads just sit on a small lip on the outer and inner
edge where the used disc was badly “troughed” and was not replaced or re-skimmed.
Turning or skimming of rotors is also recommended if not replacing discs as this removes the
glaze and polish from the surface of the discs, which can also promote brake squeal.
(Always observe the disc minimum thickness, which is in our published catalogues for safety
reasons and to avoid disc overheat).
GRAUNCHING or GRINDING SOUNDS
Can be down to the material itself, happily we have had very few complaints of this on our
pads. We have found that by putting a centre line groove in the pad, this can contribute to
reducing this noise.
We have therefore adopted a programme of centre line grooving on a large number of pads,
to reduce the incidence of this problem.
The addition of the centre line groove also totally eliminates any pad cracking in the centre
surface area of the pad where maximum heat is generated and “bulging” can occur.
BRAKE ROTOR NOISE
Created by rotors with holes or grooves, this sound is usually at its loudest when the discs
are first installed and does drastically reduce after a few hundred kilometres, when the pad
becomes flat and seated on the disc. This is not a warrantable situation and is normally “part
of the programme” as we say and has to be accepted by customers ordering grooved and
slotted discs.
SOLUTIONS WHEN NOISE OCCURS
1) Check rotor condition and “turn” or replace.
2) Allow pads to bed in properly.
3) Apply 5mm chamfer at left and right edges.
4) Use anti squeal backing if available.
5) NEVER “sand” friction material faces to eliminate noise.
|
