Squealing brakes

Dellortoman said:
I noticed that one of the pads had worn at a slight angle when I had them out. I was wondering if that might have been the scrunched up adhesive foil making the piston contact uneven.
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Typically due to pad binding in slide or caliper pin seized, depends on type fitted.
 
Yes. I figured something like that would be going on. The caliper has 2 opposed pistons with the pads located by 2 pins. A similar arrangement to the Brembo P2F08 familiar to old Italian bike owners.

The taper on the pad was actually top to bottom, not sideways. That tends to indicate a seized pin rather than pad binding where it slides against the side of the caliper. But the pins came out easily enough and didn't appear to be seized. I'm wondering if it's possible for the piston to get cocked at a slight angle within the bore of the caliper, perhaps due to a bit of grit or a gummed-up seal. I suspect I'll discover what's going on when I dismantle it.
 
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I took the Kawasaki out for a run today and the rear brake doesn't squeal any more. It's perfectly quiet and smooth. Putting a bevel on the leading and trailing edges of the pads worked a treat. Thanks to TC for the suggestion, and Marty for backing up such a ludicrous idea. I was pretty sceptical about it so I'm surprised it actually worked. You're never too old to learn something.

The Sock said:
Thinner at the top, thicker at the bottom or vice versa?
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Sorry Mr Sock for not responding. I don't remember which way it was tapered. I don't think I took proper mental note of it at the time, and now almost 3 weeks later I have no clue.
 
I have been investigating exactly the same noise on my Honda CB1300 fronts, both new Stainless rotors. Its like the sound made by resonating a crystal glass rim. I have tried everything you mentioned as well as 3 types of brake pad materials. I'm convinced it's a resonance in the rotor set off by parallel contact of the pads. I've gone back to MetalGear, the manufacturer who have done metal hardness comparison tests on the rotors for me, comparing them to OEM rotors, no difference. What I did notice was the rivets holding the rotor disk to the rotor support mount assembly were extremely tight, unlike most others which have some movement for heat expansion/contraction. So the MetalGear tech has loosened them for me. My feeling is the mechanical combination of the rotor and it's mount reinforce a resonance similar to a ringing bell. As a simple test I suspended the OEM rotors along with the problem set on a rope and struck both. The problem set rings like a bell, the OEM, nothing.
I'm expecting the modified rotors with the loosened rivets in the mail today. Will update after a test.
 
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Replaced the solid front disc and pads on a BMW F650 last week. Found thin fibre washers fitted between the old disc and hub, thought WTF? and chose to omit them as none were supplied with the new disc. Brake squealed at the lightest of lever pressure and wouldn't stop at higher pressure... refitted the old washers and all was good again.

Apparently a resonance issue within the disc, quite thin and flimsy-looking.

piet
 
And the answer is......
Got my rotors back today with the loosened buttons (rivets) for the floating heat expansion/contraction and bingo! noise gone!
As another test, they no longer ring if suspended on a rope and struck. So after trying everything else I'm convinced it was a resonance from too rigid a mounting between the disc and it's mounting frame.👍PXL_20220331_062816010.jpg
 
I have new metal gear discs on the front of the Guzzi, only 100 km on them so far, not bedded in, but rings like a bastard. Yes, the floating buttons are very tight. Did they put smaller buttons in to loosen them up?
 
If they don't move at all then what's the point, there suppose to float. That's why they cost more.
 
martymoose said:
I have new metal gear discs on the front of the Guzzi, only 100 km on them so far, not bedded in, but rings like a bastard. Yes, the floating buttons are very tight. Did they put smaller buttons in to loosen them up?
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I think the did use smaller ones, but can't be certain. I believe that would be the only way, I don't think they can be loosened.
Here's a pic of the new buttons....
PXL_20220401_073957187.jpg
 
Cutting bevels into the edges front and back on drum shoes is an age-old trick on dirtbikes, plus cutting diagonal slots in the shoes helps with deep water crossings and clearing brake dust. But beveling disc pads to a new one for me.
 
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