Bernie:
Brake squeal happens when there is high frequency vibration between the
friction material and the rotor or drum.
This vibration tends to happen when the friction material and/or the
drum/rotor glaze which is when the surface is polished to a very hard,
shiny finish. Instead of a smooth high friction drag, the brake
friction material skips on the surface of the rotating drum/rotor. This
high speed skipping makes the audible squeal that is heard.
Ok, that's what you hear. Now you have to figure what is causing it.
There are two conditions that can cause glazing. One is overheating,
where the brake surface is over used, and the other is when the material
is not bedded which is often caused by under use.
Bedding problems are usually seen on 4 wheel disc brake cars where the
rear brakes do not get adequate use, and the pads tend to polish rather
than clamp correctly. I've not ever run into this on a rear drum brake
car, so would think that more likely the rear shoes on your car have
been overheated.
The first thing to do would be to remove the rear drums and visually
inspect the linings. If you see shiny areas or cracking of the
material, then it's an overheating problem. Incorrect adjustment
causing dragging brakes is one possibility. The other possibility is a
problem with the front brakes. A failing front caliper can contaminate
the front pads on one side causing the rear brakes to overheat and
lockup.
Another possibility is a leaking rear wheel seal which can contaminate
one set of rear shoes, leaving the other side to take the brunt of
braking.
I hope this helps. I had a front caliper fail on my 1965 MGB and it
took me a couple of weeks to figure out why my rear brakes squeeled.
The sound was in the rear, so it took me a while to figure out to look
at the front brakes for the problem.
All the best
Kelvin Dodd
-----Original Message-----
From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net] On
Behalf Of bernd
Sent: Friday, June 04, 2004 7:12 PM
To: mgs@autox.team.net
Subject: squealing rear brakes
Hi all:
what in the world is causing a rear break squeal at low speed's on my
"B"?,
this is what I have done, about two months ago I replaced the wheel
cylinders
(new, not rebuild) and put new brake shoes on, drums looked to be o.k.,
I
adjusted the brakes after about two weeks of driving, may need to be
adjusted
again, emergency brake is not as tight as I would like it.
No squealing for the first month and a half or so, but now I'm getting
that
annoying squeal. Any ideas toward a fix will as usual be greatly
appreciated.
Bernie
71 MGB
Chesapeake, Virginia
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