Brake squeal

[Athame57]

Twice in the past four weeks I've had the caliper apart to copper grease the rims of the pads backing and check the leading edge of the pads themselves are bevelled, as well as greasing the caliper interior, and there is is again,  I'm at  a loss by now. Ideas anyone, apart from oiling the disc that is. 

[Johnwebley]

Put up with it for a while

But use the front brake hard!

Some times I think the disc needs a firm polish

Hopefully after a few rides it will be quieter

Sent from my SM-A546E using Tapatalk

[McCabe-Thiele (Ted)]

Might be worth thoroughly cleaning the pads and disc surfaces if you have not already done so.
Whose pads have you fitted?

[Bryanj]

I think that basically you end up living with it, since asbestos pads were banned it seems to have become a more common thing. Things suggested on both here and the US forum are, in no particular order of possibility,

Make/material of pads
Paint on outer of moving pad
Nylon ring between pad and piston
Freedom of pivot pin in caliper bracket
Crud behing caliper seal
Blocked return hole in master
Collapsing flexible brake lines
Clearance of fixed pad to disc, allong with spring
Disc surface itself contaminated, occasionally scrubbing with scotchbrite pad and brake cleaner MAY help
Play in wheel bearings

I have read posts where people swear that one or more of these will cure the problem but personally i have my doubts, i like to think of it as an alternative audible watning of approach!!!

There is also now appearing an idea that coppaslip is not the best thing, i do not adhere to that idea!

[exvalvesetdabbler]

The pads are glazed.

Put some medium grit sandpaper on a flat surface, rub each pad on that until the shine has been removed.

When you reassemble,make sure that the pads aren't dragging on the disk.  That seems to glaze the pads more quicky.

Seems to happen to me more often using modern pads

Regards
Dave

[Athame57]

The pads are glazed.

Put some medium grit sandpaper on a flat surface, rub each pad on that until the shine has been removed.

When you reassemble,make sure that the pads aren't dragging on the disk.  That seems to glaze the pads more quicky.

Seems to happen to me more often using modern pads

Regards
Dave

I think ( know ) I'll take that approach tomorrow and pray it works.  Some people think I'm being cruel to my bike!   

[Athame57]

Whose pads have you fitted?

Hi Ted
I'm not sure of the make , but they have always come from DSS.

[exvalvesetdabbler]

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

[Athame57]

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.

Hhhmmm...remember the look on peoples faces in the scene in the film JAWS where Quint dragged his finger nails down the blackboard? 
That's what people on the street around me look like sometimes when I brake! 

[florence]

For the last thirty years, mine has always squealed, different pads, various things, rubbed with emery, blah blah, always the same.  I am used to it, and feel comforted that something is happening down there.

I do not think it can be eliminated, just one of the many quirks. 

[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]

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

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]

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! 

[/b]

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.