Squealing Disc Brakes.....HELP !!

jamLCFC

I am running Magura Julies and out of the blue the rear has started squealing. Not just a gentle squesl but a full on bloody thirsty scare your kids type of squeal.

Since it started i have replaced the pads. That stopped the squeal for around a mile but it came back. I then changed the disc but still the squeal persisted. I have changed the disc again and rear wheel (not becuase of this) and now have both low efficiency and a bloody squeal. :?

The first disc i removed is on the wiifes bike and not so much as a squeak let alone a squeal.

Before i start forking out for new disc set ups any advice would be great please.

Thanks all

The Rookie

Squealing when braking or when not or both?

Squealing is a resonance issue, make sure the callipers are rigidly mounted, you could try different (stiffer OR less stiff) mounting adapters.

Simon

jamLCFC

it only squeals when the brake is applied.

These have been fitted for over a year with not a single issue in that time. The pads that i had removed still had loads of life in them so is it still likely to be a caliper mounting issue?

The Rookie

It can be lots of things, at the end of the day its a resonant frequancy being exited by something, so pad material, disc pattern, calliper and mounting arrangemnt stiffness and so on....sometimes you just have to live with it!

If your using Organic pads you could try sintered or vice versa.

Simon

jamstaa

Well as you've already changed the pads so it can't be a wear indicator, and you've degreased the discs I'd go back to basics and make sure everything is aligned correctly.

Make sure the discs straight, and the caliper is centralized to the disc, also you said you are down on power, so as you've made sure the discs aren't greasy/polished by a lube or water disperser of some kind. Are both pistons working equally? doing the same work? If one is ceased or not working correctly it'll twist the disc out of align with the caliper vertically, one piston would theoretically get hotter as it's pushing disc against the other pad instead of the disc being squeezed could cause a squeal ?

I had a problem with power and squealing... i noticed too much degreaser had caused one of my pistons to stick and sure enough everything was twisting. I dabbed a very small amount of thin lube on the seal and used a soft tool to gently hold the working piston in whilst i moved the lever a little (very carefully as to not push the piston out too far) i then would push it back and do a couple of times... sure enough the power came back... and squealing stopped.

the only squeal i've had since then is if i use gt85 or silicone on the frame and it gets a little on the disc.. it'll reduce efficiency a little (unlike grease the kills it completely) but will make it squeak annoyingly. You then have to whole thing of degrease the disc and cleaning off the pads.

Obviously they can still squeal if i'm using them hard and i don't think you can do anything about that.. but gentle breaking where the temp isn't too high they are fine.. I use sintered pads, so not sure how resin pads would effect anything.

sorry if i'm insulting your intelligence.. but good luck.

jamLCFC

jamstaa wrote:

sorry if i'm insulting your intelligence.. but good luck.

Far from it. I will start to work through your suggestions tomorrow....

had a bit of a brainstorm...

As the wifes running the same brake set up i will try pads from hers (they dont squeal) and see if they do in my set up. If they do then is it fair to say its a caliper issue?

cooldad

Or sometimes they just randomly squeal.

bennett_346

My brake gobbles on the 203 rotor. And the sintered pads make an awful squealing racket.

jamLCFC

well after a pleasant afternoon chopping and changing pads and discs from bike to bike the conclusion is that it has to be the caliper.

The wifes disc set up regardless of discs or pads doesnt squeal at all. Place the same discs and pads onto mine and squeals like an ickle piggy...!!!

I have checked the caliper over and one of the pistons seems to be a bit slower to move and retract so could very well be a major contributing factor.

thanks all !!



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pilsburypie

I know some will jump on me for saying this but I have cured all my screetching brake issues with a careful thin smear of copper grease on the metal back of the pad.