Squealing Brakes

[Manfred]

I recently (300 miles back) put new BMW brand brake pads on my '87 R80RT. They work just fine, but squeal in a most unpleasant manner under moderate braking - which is how I come a stop most often.

What must I do to be saved from this horrid noise?

[Major Softie]

Permatex (and some other companies) make a product to fix your problem. It's a gooey glue-like product that is put on the backs of the brake pads. The squealing is from vibration of the backs of the pads against the pistons.

[Manfred]

Must one remove the pads to apply this magic goo?

[ME 109]

Must one remove the pads to apply this magic goo?

Yes.
The pads can be removed without removing the calipers.

I have metal king pads at the mo and suffer the same problem.
I used a similar product, the name of which I can't remember.
The squeals came back.

I've not had squeeling brakes before in 18 years.
Perhaps there is an indication of calipers/piston condition?

[Tony M.]

I put my R80 back on the road yesterday after sitting in the garage for three years and it is my back drum brakes the are squealing loudly. I'm hoping it is merely disuse and that as I ride it the noise will stop.

[ME 109]

Squeeling discs are quite a phenomenon.
The squeeling can be produced on the front wheel with the bike on the centre stand, with 'very slow' rotation of the wheel, perhaps one rotation per minute.
This is with the front brake off.
Very consistent movement is required to produce this loud squeel.

So there is a district difference between my little experiment with the brake off, and squeeling brakes with considerable pressure applied under road braking conditions........

I wonder if I qualify for the Nobel peace prize?

[Manfred]

Squeeling discs are quite a phenomenon.
The squeeling can be produced on the front wheel with the bike on the centre stand, with 'very slow' rotation of the wheel, perhaps one rotation per minute.
This is with the front brake off.
Very consistent movement is required to produce this loud squeel.

So there is a district difference between my little experiment with the brake off, and squeeling brakes with considerable pressure applied under road braking conditions........

I wonder if I qualify for the Nobel peace prize?

You might qualify for the Manfred Peace Prize if you help me correct my squeal problem, which started after putting new pads on.

[ME 109]

You might qualify for the Manfred Peace Prize if you help me correct my squeal problem, which started after putting new pads on.

Right then, the symptom is squeeling brakes. Apparently, vibration causes the squeel.

The conditions which allow vibration/squeeling, would be unequal pressure across all contact surfaces.
That is, caliper piston to pad back, and pad front to disc.
I think the main culprit will be the contact 'ring' of the caliper piston.
Proof of this may be obtained by removing a pad/s and observing the contact mark on the back of the brake pad.

Less than a full circle contact mark would suggest a worn contact surface on the caliper piston. This could allow for lateral vibration, much like a woodwind reed.
This could be remedied by machining said contact surface on the piston, or replacing the piston with a new one.


* All pure speculation of course.

Where do I pick up my prize? Can you mail it?

[Manfred]

While I thank you for your willingness to earn the Manfred Peace Prize, the standards are high and not yet met. Why would new pads cause the condition you describe? No squeal with old pads (about 3/16th in left). Pistons lubricated when new pads installed; squeals begin.

[ME 109]

I thought you would ask that Manfred.

Eh-hem, well, the old pads have worn to the contour of your pistons, creating full, or near enough to it, contact.
The pistons have slowly worn over the years because there is more pressure/wear applied to a particular part of the piston 'ring'
Maybe at the last pad change x miles ago, there was not quite enough wear on the piston, and new pads quickly settled in to any irregularity.
Did you do the last pad change?

This latest pad change has provided the least contact possible between the pad and piston, creating the ideal squeel criteria.........

The above theory should be read in conjunction with the knowledge of who wrote it.

Now, about that MPP?