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Brake squeal

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Johnny4428:
I’ve always had an issue with the 550K3 but never had a squeak out of the K1. Would need to compare and see where I bought pads for K1. Incidentally was a new Caliper fitted to K3 when restored.

McCabe-Thiele (Ted):
Anecdotally I think there are many factors involved, I have found in the past that hard pads are worse than soft ones for making a noise.

K2-K6:

--- Quote from: exvalvesetdabbler on September 27, 2026, 06:53:51 PM ---The ones that I have are EBC and they still start to squeak a little after about 500ml   Previous ones were from DSS bought in the mid 90s squealed like a stuck pig.

I have the nylon ring still in there, makes no difference, just makes the braking effect a little more progressive.   What makes a difference is cleaning out all the corrosion in the groove that the seal occupies, not just gunk or bits of old seal, the corroded aluminum crust.  Failure to keep this groove clean makes the piston tight and it doesn't retract properly or enough.  With the front wheel off the ground it should spin easily with one finger with minimal rubbing sound of the pad on the disc.


Regards
Dave

--- End quote ---

I understand the same and agree with reasoning.

Some time ago and working with competition pads for rally, there was good advice available direct from brake and pad manufacturers which also agreed.

Effectively, the pads are under used * and become polished to fine degree in surface "refinement" such that they give a bite then skip effect to set up a resonant frequency within the metal disc. They explained it like resin on a violin bow, that to force the strings to skip and provide the resonance in the instrument.

What does * that mean "under used" ? In their case it was high heat range competition pad materials used at below their intended heat and duress range, and very vocal output it makes too.
In our gentle roadbike user case, its replicated if the pads are dragging on the disc continually  ..... above a minimum system expectation. Effectively to continually polish the surface while rotating 100% of the time. Which is ultimately because the pads aren't competently retracted from full braking contact as they should.

It's not to say that the seal operation (as noted in previous post) is always the absolute/only cause, but mostly will be the root of a problem regardless. In effect, practical steps otherwise can't be taken and evaluated with out this part working correctly.

Often the brakes don't get a reasonable examination as it only takes a very small amount of drag to cause this, which may go unnoticed by the inexperienced in checking them. It is quire often accompanied by slightly "wooden" feel to brake lever ifseal is really impaired for it's movement as tge hydraulic system doesn't complete it's retract operation fully when brake is released. 

Athame57:
I took my pads out and rubbed them hard on the pavement, squeaks and squealing stopped.  :)
In the meantime my drum has started squealing, no peace for the wicked!  ::)

K2-K6:

--- Quote from: Athame57 on October 07, 2026, 11:27:24 AM ---I took my pads out and rubbed them hard on the pavement, squeaks and squealing stopped.  :)
In the meantime my drum has started squealing, no peace for the wicked!  ::)

--- End quote ---
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Undo the rear wheel spindle just until you can move the spindle a little, then get someone to hold the rear brake on quite "generously" so it's clamped good and tight. Now tighten the spindle to correct level again.

Then assess it like that.

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