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I wonder if anyone has experienced this or something similar and can shed some light on this for me

I've got a cyclo cross bike with the Shimano RS505 shifters and RS785 hydro calipers. When I first set them up, everything is fine. I go through phases of not using the bike a lot (tend to ride the road bike more often as I'm a fair weather cyclist), yet when I do, I find the brakes squeal terribly - almost like there is oil all over the rotors, front and back. Around christmas time I re-bled everything, and fitted new pads and rotors. I used the bike quite a bit then and everything was fine. The front brake has however got noticably soft (The pad is quite worn), yet I though it should self-adjust?

I've just got the bike out after six weeks or so of non-use and gone to check it over - the brakes squeal with the tiniest pressure again. I can't see any signs of leaks, there is no sign of oil anywhere, so I'm at a loss to explain it.

Can anyone shed any light?

24 comments

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Ogi [110 posts] 6 months ago
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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?

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stub [12 posts] 6 months ago
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Hi,

I'm using the stock Shimano XT/SLX resin pad (J04?). I figured it best to replace the originals (using the XT RT81 rotors too).

I always bleed with the bleed blocks (wheel off, no pads fitted) to avoid contamination. Initially the bike was fine when I rode it for a couple of months in winter. I put it back in the garage, got it out yesterday, squeals terribly.

No brake rub at all (I centered the caliper post-bleed last time and it had been fine) - it's only if you apply the brakes.

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Ogi [110 posts] 6 months ago
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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.

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bauchlebastart [123 posts] 6 months ago
3 likes

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.

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stub [12 posts] 6 months ago
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Hi bauchlebastart,

I'm beginning to think that is the cause. Did a replacement caliper cure your problems? I'm just wondering if I'm doing something wrong to cause it...

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part_robot [259 posts] 6 months ago
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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.

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HalfWheeler [640 posts] 6 months ago
1 like
bauchlebastart wrote:

Leaking piston seals?

This. 

Had a smiliar problem with my Kona Cinder Cone. Went through umpteen calipers (mostly on warranty) before I figured out what was happening. This may not be the case with you but it was where I was storing the bike that was the problem. I have an Asgard metal bike shed, freezing cold in winter, boiling hot (like a parked car) in summer. Over the course of the year the seals would expand, contract, etc etc. The seals couldn't take it. Fluid would leak onto the pads. Result; screeeeeech!

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CXR94Di2 [1723 posts] 6 months ago
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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

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bauchlebastart [123 posts] 6 months ago
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stub wrote:

Hi bauchlebastart,

I'm beginning to think that is the cause. Did a replacement caliper cure your problems? I'm just wondering if I'm doing something wrong to cause it...

 

On both occasions, yes. Calipers replaced and the issue went away.

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kev-s [271 posts] 6 months ago
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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

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stub [12 posts] 6 months ago
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Thanks for all the responses - reading through I'm convinced that it is the pistons leaking.

I think I'm going to have to bite the bullet and remove the calipers and send them back. Only problem is the place I bought them from is no longer trading so I'll have to try and persuade my local LBS to send them back for me....

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risoto [23 posts] 6 months ago
2 likes

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.

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DaveE128 [904 posts] 6 months ago
1 like
risoto wrote:

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.

Are you using any kind of spray lube, polish, WD40/GT85 etc on the bike? You really want to avoid getting these on disc rotors.

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dunnoh [214 posts] 6 months ago
1 like

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

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IanEdward [120 posts] 6 months ago
1 like

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...
 

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kevvjj [247 posts] 6 months ago
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IanEdward wrote:

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

It ain't just Shimano. Avid/SRAM, Hope, Formula, Hayes etc etc there isn't a brand on the market that doesn't squeal when wet. I've tried every type of brake compound ever invented, all to no avail. I'm afraid it's par for the course... just like the noise carbon rim brakes make all the time on a decent descent.

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rnick [130 posts] 6 months ago
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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.

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CXR94Di2 [1723 posts] 6 months ago
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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.

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IanEdward [120 posts] 6 months ago
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Sorry I meant Shimano had been sitting on issue of leaking seals for years.

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

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newtonk [43 posts] 6 months ago
2 likes

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.

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dantheman1979 [5 posts] 6 months ago
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bauchlebastart wrote:

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.

I had the same problem so I replaced the discs and pads but this didn't fix it. I replaced the calipers as it turns out the pistons where sticking in my old calipers and it's been fine now for a few months. 

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matthewn5 [1059 posts] 6 months ago
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risoto wrote:

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.

I noticed this on the Dunwich Dynamo last year. Squealing brakes through quiet villages at night don't make many friends.

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IanEdward [120 posts] 6 months ago
1 like

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! smiley

 

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...

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Johnnyvee [95 posts] 6 months ago
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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.