As I said here:
http://www.fordforums.com/showthread...ghlight=brakes
All brakes make a noise; it's just usually at a frequency that the human ear can't hear (think about it; what would you expect placing any material against fast spinning steel disk). That said, the ability to hear the brakes is usually caused by the pads vibrating although brake pad dust and rough disk can also be contributors)
Ways to fix it are:
a) Use CRC Stop Squeal (pink adhesive goo) available from Repco and most autopart places. This rubbery adhesive goes on the back of the pad and in 95% of cases stop the audible squeal. I use it all the time on all 3 of my cars.
b) If this doesn't work you can cut a radial groove (same direction as if you had spokes in the wheel) in the pad with a hacksaw in the middle of the pad. Cut down to within about 1 or 2mm of the backing plate. Some good pads already have a radial groove or cut in the middle of the pad for this reason.
c) Chamfer the leading edge of the pads (the short side) so the angle of incidence with disk is around 45 degrees. Just grind or cut the corner off the leading edges (just about 5 mm usually).
Also remember when fitting new pads to remove the glaze from the dics by lightly scuffing them with fine emery paper or similar.
These will not inhibit the performance of your brakes and are standard Porche approved remedies.
See: the sites I mentioned as well:
http://www.delphi.com/pdf/sae/1999-01-0142.PDF
[url=http://www.sts.sae.org/membersonly/techinfo/servicetech/tech-tidbits-05.pdf[/URL]
http://www.mscsoftware.com/support/l...o99/p01699.pdf
To quote a a couple of research engineers for example:
Quote:
Disk brake squeal occurs when a system experiences
very large amplitude mechanical vibrations. There are
two theories that attempt to explain why this occurs. The
first theory states that squeal is a �stick-slip�
phenomenon. The second theory believes that the high
levels of vibration result from geometric instabilities of the
brake assembly. Both theories attribute the brake
system vibration, and the accompanying audible noise,
to variable friction forces at the lining-rotor interface.
According to the first hypothesis, a variable friction
coefficient with respect to velocity provides the energy
source of the brake squeal. For the case of geometric
instability, the second theory, the variable friction forces
are caused by variable normal forces. Even if the
coefficient of friction is constant, variable friction forces
are still possible. Both theories have been discussed by
researchers, but previous brake squeal experience and
the majority of research literature considers the
geometric instability to be the major phenomenon of
brake squeal. MTS has adopted the geometric instability
theory to analyze brake squeal.
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If your post grad maths isn't rusty have a read of the rest of this article. Also see
http://www.mscsoftware.com/support/l...o99/p01699.pdf
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