Permanently squealing RS785 disc brakes

Haven't swapped calipers, as they are new too.  In addition, when I put the new rotor and pads on, there was an immediate squeek, really no time for oil to hit the pads or rotor.

Any updates on your squeeky disc brake fixes?  I'm asking because I am at my wit's end.  Have tried just about everything written, expressed or implied.  Cleaning, new rotor, new pads, cleaning again. However this only occures with a certain rear wheel. I can swap wheels and I don't get the noise.

I'm running 140 Ice Tech Shimano's, so they are centerlok's. 

Haven't tried the talcum powder yet, but I don't see how that could be  a permanent fix.

Sometimes this can be caused by the bolts or centrelock holding the disc in place being loose. A friend of mine went down all kinds if routes to stop squeals and it was the rotor fixing bolts.
Just a thought and costs nothing to check.

Well I had some partial success today on a very wet cold commute.

By pulling frequent, hard stops and attempting to drag the brakes as much as possible, they were slightly less screechy than usual, although I noticed an alarming and slightly obscene amount of vibration coming through the seatpost when using the back brake hard.

Also all the additional braking gave me some valuable interval style training, although it made my commute about 10 minutes longer...

Disc brakes, the wave of the future! 

Joking aside, I'm going to the bike shop today, maybe see if they'll consider new rotors and pads trade price at least. I notice Magura rotors (or a similar looking Spanish brand called 'Galfer') have loads of cut outs and edges and are designed to work far more quietly in the wet. I'd love to reduce the size of the rotors as well so they heat up more under braking, but I don't think adaptors exist to reduce rotor sizes, only increase...

Same problem here, as mentioned on another thread - I honestly think any bike shop in a flat area selling bikes equipped with these brakes without asking the buyer about their riding style is doing their customers a massive disservice. 

Using my hybrid to commute in London, it's just not possible for me to use these brakes hard enough to overcome the squealing or wear in the pads/rotors or whatever else it is you're supposed to know/do to get brand new brakes on a brand new bike to function correctly and below the decibel levels of a jumbo jet.

Like many others, when it's wet I now use my rim brake road bike instead - exactly the opposite of what I intended when buying the hybrid. 

Buying a new bike for commuting in a flat area?  You might get lucky or you might not, but don't bother with disc brakes would be my advice.

Sorry I meant Shimano had been sitting on issue of leaking seals for years.

I like the 'emperor's new clothes' analogy though!

I have 5 bikes with disc brakes, its the compound of the pads. All squeal to some degree. Much less so with sintered pads. I've cleaned my disc rotors with brake cleaner after a wet ride and the noise has immediately gone until it rains again. I change my pads to sintered much much quieter.

It's par for the course I'm afraid.  Based upon my MTB experience, I used to find braking in wet conditions particularly noisy if the bike had just been cleaned.  Riding through the nearest dirty muddy puddle seamed to fix the problem - so I put it down to a surface "glaze" or similar.  To an extent, disk brakes are the emperor's new clothes - sure they're great when they work, but get some oil on the disc / pads and you're binning the rotor & pad, unlike car  & motorbike brakes, road bike brakes don't generate sufficient heat to  burn off the oil.   With a rim brake, such situations are often salveagble.

The worst thing is Shimano just seem to be sitting on this issue, it's been happening for years!

My dad treated himself to a brand new, flat barred Giant Road Bike with Shimano Hydraulics for his retirement, and never rides the thing as the brakes are just so noisy (oh, and they rub too, despite repeatedly being reset with a Hayes Calliper alignment tool). I've just spent afternoon sanding rotors, blowtorching pads, trying to find leaks, cleaning pads, re-installing and trying to bed them in again, and I strongly suspect it won't have worked.

I don't buy this excuse that oil and grease get thrown up from the road either, if this is the case why are the brakes being sold on road bikes and commuters?

Also, I think the industry needs to give riders better advice on what disc brakes are actually good for, and what not. Commuting being a good example of perhaps when disc brakes are not worth the slightly improved braking response.

My commuter is cursed with screeching noisy disc brakes in the wet, so much so that I take my far less advanced/expensive rim braked commuter out when it's wet. Maybe if I commuted through the Lakes or the Cairngorms this wouldn't be an issue, but since Edinburgh's ex-railway line cycle paths are all invariably flat I never do enough braking to warm the pads or the rotors up.

Perhaps the manufacturers need to develop a pad which works despite infrequent use, and doesn't screech in the wet. Perhaps some sort of compound which doesn't glaze over and is siped to clear water from the disc. A compound that doesn't instantly soak up every little impurity out of the spray from the road would be handy too...
 

Try Muc Off Disc Brake cleaners.  It seems to do the trick

Sorry, but that  is why I absolutely hate disc brakes. I got some mechanical Avid BB7 brakes, so no fluids, and they are ALWAYS noisy - from the very beginning I bought the bike. Everything has been cleaned and adjusted several times. Goes away for a few rides. Then squeling terribly again. This happens in the dry  and the wet. I keep my bike clean and still..I am conviced that  the slightest dirt on rotors provoke it. When I clean them with alcohol it goes away for a while=1-2 rides. You can't even see that the rotors are 'dirty' enough to provoke anything. I have never had a problem with caliper brakes. In the future I will avoid disc brakes like the plague! Same thing happened with my first bike with hydrolic disc brakes. that was Shimano and just as noisy.

Deffo leaking caliper

Had this on a shimano zee brake caliper a while ago

All was fine when new then after a while it squealed, new pads, good clean and all was fine, bike sat for 3 weeks went to use it and brake squealed again

Luckily it was under warranty, sent it back to chain reaction, they couldnt find a leak so they sent it back to shimano who pressure tested it and found one piston was leaking under pressure

It's the resin pads, when they get wet they deposit lots of material on the rotors. Clean the rotors with alcohol or brake cleaner thoroughly. This should eliminate the noise. It will come back when the pads get wet again. Upgrade to sintered pads, these are much better against squeal noises

Grease kicked up from the road is usually the culprit. Bloody polluting cars!

Remove pads and clean with Isopropyl alcohol (or replace). Remove rotors and do same. Hold discs with something heat proof, pour on alcohol and ignite. Do a few times. Let cool. Re assemble everything. Take bike to steep hill ideally without using brakes on the way there. Cycle fast down the hill and apply front brake to medium strength down to a jogging pace and then hard as you can. When you almost stop let go; do not let the wheels stop rotating. Keep going like this down the hill; fast-slow-fast-slow etc. Go to the top again if necessary and do again until you've  braked about 20 times. Discs will get really hot! Repeat with rear brake, with bum sitting over the rear tyre for extra traction. 

Result; perfect silent braking in all conditions.

Leaking piston seals?

Happens often with Shimano hydro calipers.

Ive had this problem on two bikes, squealing rear brake, no power but no signs of leaks. Cleaned rear disc and replaced the pads, all was fine for a week then the problem returned. Had to replace the entire caliper as Shimano dont provide spares.

Weird one. I don't know,  try cleaning the rotors with alcohol. If not, leave it for while for the pads to bed in and check it out if it keeps coming back later. It might help to take a steep descent and step on the brakes a bit, to maybe remove this top film/layer that seems to be the problem. I assume you're talking of this extreme squeeling in dry weather, bcs in the wet -  this is expected to some degree with some pads.

Hi,

Do you mind me asking which pads did you use? They might be of low quality.

Secondly, by any chance did the oil spill on the pads/rotors when you were bleeding? If so, there you go.

Do you have any brake rub on the rotors?