Re: squeaking brakes

[Regan Dale Copple <copple@cory.EECS.Berkeley.EDU>]

N. Razvi,
	If those pads are disks then the problem lies in the surface
mating between the hydraulic brake cylinder and the back of the pad.  If
the pad is allowed a little slip when the brakes are depressed and the
cylinder comes into contact with the brake pad, it will vibrate.  This is
the squealing noise you hear.  When the brakes pads were replaced, whoever
did it may have sprayed a rubber or plastic noise-dampening compound onto
the backs of the pads, eliminating most of the noise.  However since the
pads can still slip, when you back up the cylinder scrapes the compound
from the back of the pad, hence the squealing in reverse.  Given enough
time and enough reverses, the cylinder scrapes enough of the compound off
so that the brakes squeal constantly.
	Now you say it is a squeak and not a squeal, the difference in the
noise could mean a different problem.  A squeak is an impulse noise, like
a knock on a door or a gunshot, a squeal is a noise of indeterminate
length.  Also it could be a different problem if you have drum pads and
not disks, I don't know.  The first step is to characterize which type of
brakes that you do have and then to isolate exactly what type of noise is
it and where is it coming from. 

> I recently had a pair of front brake pads fitted and after a few days 
> they started to squeak. I've taken them back and they've filed them 
> for a better fit, so they say. At first they seemed o.k this time only squaking 
> when the car rolls back, but now after 3-4 days they squaek all the 
> time when the car comes to a final holt. I've done 500 miles since 
> they were fitted so they should have wore in by now. I had Ferrodo 
> pads fitted on a 146 Boxer. What to do now?

	If they do turn out to be disks then the solution is a simple one,
go to an auto parts store, buy some brake-squeal stop (usually comes in an
aerosol can), jack up car, remove brake pads by relieving pressure on
cylinder, spray backs (BACKS, NOT FRONTS) of brake pads, and re-install.
Goodbye noise, at least for awhile, sometimes it can come back because
again the pads slip and can rub the backing compound off.  I hope this
helps, because I hate squealing brakes more than anyone.  Ciao!

				Regards,
				Regan Copple
				79 Spyder "vroom, vroom"
				73 Montreal "VROOM, VROOM, crackle, pop!"