Could I have *finally* found the reason for squeal hell?

T_dog
T_dog Posts: 14
edited April 2020 in Workshop
Howdy,

Bought my first road bike (BMC GranFondo 01, 105 Disc) about 2 ½ years ago. From very early on it's had squeaky brakes. Other than that I really can't fault the bike.

I took it back to the retailer and they replaced the rotors and pads. I've tried all methods of cleaning the pads, but the only thing that cures it is new pads, and then these don't last long before squealing again - like about 1-2 rides of about 100 miles in total. It's ben a constant stress.

However, on changing them again yesterday I noticed that on the old ones (well, not that old) there was a piston sized ring of oil on the back of the pads - as in where the pistons apply the pressure to close the brakes on the rotor. The circle isn't complete, ie the bottom of the circle bleeds into the pad itself - pics below. Should a braking system be depositing oil so near/on the pads?

Could this be the root cause of the problem, and if so, what's the solution?

Many many thanks in advance 🙏



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Comments

  • T_dog
    T_dog Posts: 14
    The brakes are Shimano BR-R785 Hydraulic
  • T_dog
    T_dog Posts: 14
    That's what I thought. Any ideas as to why that might be happening, and if it's the cause of my deafening squeal? And also what the remedy might be?

    Many thanks
  • veronese68
    veronese68 Posts: 27,309
    Contaminated pads will squeal and that would cause contamination if it gets onto the pad material. But I would also expect the brakes to feel spongy if they are leaking fluid. Have you ever had to bleed the brakes?
    I think those brakes have a ceramic piston and I've seen others complain of a cracked piston leaking, that would necessitate a new caliper unfortunately. Is it doing it on both brakes and are both brakes squealing?
  • T_dog
    T_dog Posts: 14
    Thanks for the reply. Yes, the squealing happens to both back and front brakes. I clean the pads off - usually with alcohol and/or using a degreaser like Fairy liquid - they look clean again, then after a short ride they are black - looking like they've had 100's of miles of riding on filthy roads.

    Brakes don't feel particularly spongy, although having said that they do feel sharp as a knife when I put new pads on. At the end of the winter my rear brake needed bleeding - was totally gone. I assumed I must have inadvertently pressed the brake lever when the wheel as off. Front has never needed bleeding.

    New caliper... is that pretty much an entirely new braking system, or just the one part that can be purchased for not too much..?😬
  • T_dog
    T_dog Posts: 14
    TBH the use of fairly liquid is only the most recent in a long line of ways to reduce the gunk on the pads. The persistent, deafening squeal has been around way longer than me reaching for the Fairy. Got the idea from this video:

    https://youtu.be/08ePb4_C0JA

    Conversely on my MTB I've never had to even remove the pads. And those things get exposed to all sorts of muck, grime and dust and dust.

    Still thinking the oil on the back of the pads is a massive tell tale sign, no?
  • T_dog
    T_dog Posts: 14
    I’m quite good at taking measures to avoid the dangers of freshly oiled chain spray (always wipe chain after piling etc) and the problem is just as bad - is not worse - with the front brake
  • rwoofer
    rwoofer Posts: 222
    I've been having loads of problems with brake squeal on one of my bikes that isn't used so frequently. Recently I went on a long downhill dragging my brakes deliberately and they are now much better. Still squeal a bit and possibly more persistant dragging will get rid of the noise completely.
  • T_dog
    T_dog Posts: 14
    Tried that. Many many times. Unfortunately, it didn’t do the trick. 😞
  • veronese68
    veronese68 Posts: 27,309
    I also hold with the keeping chemicals and such like well away from the pads so would avoid the Fairy. The fluid on the back of the pad does seem most likely, but if fluid gets out air should be getting in giving a spongy feel, this still confuses me.
    Going right back to very basics a squeak is caused by contamination or vibration. As it does go away for a while iniially it should mean everything is tight and lined up properly. So contamination seems most likely.
    If fluid is escaping I believe a cracked piston is probably the cause. Is the fluid only on the back of one pad? Have you ever noticed that before? It should be possible to change just the caliper, much cheaper than a whole new system. Is the hose joined with a banjo bolt or straight into the caliper with an olive on the end of the hose? Can't remember. If a banjo bolt you should replace the washers, if an olive that should be replaced. Fit the caliper then fill the system and bleed it, make sure the disc is completely clean using IPA, isopropyl alcohol not the beer. If that doesn't work please ignore this post ;-)
    Good luck.
  • lesfirth
    lesfirth Posts: 1,382
    IMHO you have 2 issues here.Fluid leaking onto the back of a pad and noisy brakes. The two are not related.
    The tiny amount of fluid leaking out will be replaced from the master cylinder reservoir. Air will not get in and braking will not be affected unless fluid gets onto the disc side of the pad. I recommend that the problem is fixed ASAP.
    To fix your noise clean the disc by rubbing the braking surface with" wet or dry paper" .( As an apprentice I refused when instructed to go the stores for some of this. I thought it was like a long wait.) Then clean with brake cleaner.The disc is best cleaned off the bike. Either fit new pads or try removing the pad surface by rubbing the pad on some "wet or dry" on a flat surface. Bed in with some heavy braking. If the pad cleaning does not work clean the disc again before you fit new pads.
    In the car trade it is standard practice to put a smear of copperslip on the back of pads, where the piston pushes, to stop brake squeal.I do it on my bike.
    Good luck.
  • Charlie_Croker
    Charlie_Croker Posts: 1,698
    I agree with veronese68 contamination=squeal. Whether the two things are related or not, you need to stop hydraulic fluid leaking past the pistons, this is never acceptable. Replacing the seals, is the obvious thing to do, I had a quick search, but I can’t find any to fit your particular callipers (Shimano BR-R785 I think). If you can find some seals to fit this is what I’d do. Then replace the fluid with the correct type of course, clean the pads and rotors. Test.



  • T_dog
    T_dog Posts: 14
    So this week I put new pads in. Did an undulating 20 mile ride. All perfectly silent. Bliss.

    On the last descent to my house, just as I was coming to a stop the front brake started to squeal. Nothing horrendous, but I've heard this so many times I know it's the start of what will be deafening.

    I've just taken the pads off the front - see below. Ring of oil on the back, an the pads are discolouring already - after just one 20 mile ride!

    I also noticed that the new pin that holds the pads in place (that came with the new pads) had oil on the two places where it passes through each pad - so there's definitely oil around those pads!

    Think it's time to call in a professional. A bit pi55ed off if I'm honest as it's been back to the place I bought it a number of times and on each visit there's been a scratching of the head and I've left the shop with new pads... which sorts the problem for a couple of rides at best. And now it'll be our of warranty



  • T_dog
    T_dog Posts: 14
    I’m in Sussex - about 12 miles north of Brighton. I spoke to the retailer today. They are a national chain who’s HQ is in this neck of the woods.

    They were great. Explained what I’d found and he seemed to think that I’d found the cause.

    Unfortunately they have no mechanics in at the moment, but he has said that I can bring it in in a couple of weeks and they’ll have a slam fine look at it and replace the callipers if that’s what’s needed.

    I would like to get it sorted with a working mechanic before then, but as that will mean having to pay for 2 new callipers I reckon I’ll hold out.

    MTB and family hybrid bike rides it’ll have to be for now 😊
  • Charlie_Croker
    Charlie_Croker Posts: 1,698
    oxoman said:

    T-dog, what part of the country are you in. Perhaps between forumites we can point you in the direction of a decent bike shop or bike mechanic.


  • T_dog
    T_dog Posts: 14
    There’s a mechanic round these parts called The Cogfather... anyone know/rate him?
  • veronese68
    veronese68 Posts: 27,309
    If the bike has been back repeatedly to the shop you bought it from they know the problem started in warranty and they should offer some sort of assistance I'd have thought. They should certainly argue on your behalf for replacement parts free of charge.
  • manxshred
    manxshred Posts: 295
    In the mtb world, shimano brakes are well known for leaking oil in the calipers, leading to noise and decreased performance. Just google "shimano leaking caliper" and you will see lots of talk.

    You can't get parts, normally just have to replace the caliper.
  • T_dog
    T_dog Posts: 14
    Thankfully my MTB brakes are Shram
  • Charlie_Croker
    Charlie_Croker Posts: 1,698
    manxshred said:

    In the mtb world, shimano brakes are well known for leaking oil in the calipers, leading to noise and decreased performance. Just google "shimano leaking caliper" and you will see lots of talk.

    You can't get parts, normally just have to replace the caliper.

      I've done some reading having searched as suggested and what I have read is quite worrying. Not only is the caliper piston seals suspect but also the transfer port seal between the two halves of the caliper. A lot of Shimano brake calipers seem to suffer the same problem. To add to the problem Shimano are allegedly deigning there is a problem.
      I even found an old thread (Shimano brake caliper, leaking seals) from 2012 on this forum, no solution other than to replace the calipers.

      With this new knowledge, first thing is to identify where the leak is coming from. So remove the wheel, remove the pads. Clean the whole caliper, make sure it’s all clean and dry. Pop a piston wedge or block of wood in where the pads/disc would normally be. Use a ty-rap or bungee cord to hold the brake lever tightly on. Leave overnight. Probably best if the cycles placed upside down for while doing this, also wrapping a piece of toilet paper (not kitchen roll) around the block of wood/pistons to catch any leaks. Hopefully you’ll be able to identify which seal is leaking and then replace it.

      If you cannot get hold of new piston seals or a thicker O ring for the transfer port there’s one more suggestion I have. You’ll need mix some (one drop only with a pipette) amyl nitrate with some hydraulic oil and bleed this into your brakes. If you can get hold of it, I haven’t seen any for sale in years. It’s used in model diesel engines as an ignition additive among other things, it’s quite expensive, but you only need two drops (less than 1cc) one for caliper. The amyl nitrate will cause the seals to swell, sealing the leak.
    P.S. Don't confuse amyl nitrate with amyl nitrite
  • Charlie_Croker
    Charlie_Croker Posts: 1,698
       As a footnote, if you do decide to take the pistons out you may as well measure (or have somebody measure) both the pistons and the bores. To see if there round and consistent all the way along. Also check the tolerance between the two.

       I read or hear if not on a daily basis then certainly on a weekly basis, about poor engineering or quality control in relation to bicycles being sold to the public. Shelling out sheds loads of cash for a product is no guarantee of quality, it would seem.
  • manxshred
    manxshred Posts: 295
    Another option is to replace the caliper with the Hope road calipers, post or flat mount as needed.
    https://www.hopetech.com/products/brakes/road/

    I've run R785 brakes on my road for 5 years now without problems, but is always in my head that they could go.
  • T_dog
    T_dog Posts: 14
    Thanks for all the input folks. Gonna give the retailer a chance to solve the issue in a couple of week’s time, once the lockdown thing starts to lift.

    If they don’t come up trumps - which unfairness I think they well - I’ll certainly be in the market for new callipers, and ideally a different kid this time. The articles out there about leaky Shimano callipers is a tad worrying!
  • shipley
    shipley Posts: 549
    edited May 2020
    If you get stuck and need help - Dave Wilkes is in Billingshurst and runs onsitecycles (dave@onsitecycles.co.uk) and will come to you and do the work in his van. He's very thorough and highly recommended. He's an ex MTB chap so this kind of problem will be just up his alley.
  • T_dog
    T_dog Posts: 14
    Well, after a long wait - partly Covid related, but also partly related to the fact that the callipers I had are no longer made, and that the nearest compatible callipers only came as a full set, and partly because calling Madison during these lockdown times (for a warranty conversation - bike is approx 3 years old) was impossible, aforementioned national chain came up trumps.

    Put new (upgraded) callipers on and didn’t charge me a bean.

    Can’t wait to get out and be squeal free 😉
  • pilot_pete
    pilot_pete Posts: 2,120
    Which callipers did they fit out of interest?

    PP
  • T_dog
    T_dog Posts: 14
    SLX. Turns out when I got my bike disc brakes on a road bike were still v new and they fitted MTB brakes (or at least fittings). As road bikes with disc brakes have evolved the callipers that fit my bike are more/only likely to be MTB ones.
  • pilot_pete
    pilot_pete Posts: 2,120
    Thanks. I have RS785 on one of my bikes. Never had a problem with them. The reason why only a mountain bike brake would fit is because road bikes have gravitated to a flat mount standard and the 785s are post mount.

    I also retrofitted a new 105 groupset to my winter bike, which is post mount. I had to buy some Deore calipers to match, which are cheap and work flawlessly.

    PP
  • Charlie_Croker
    Charlie_Croker Posts: 1,698
    I’m glad you’ve got a result in the end T_dog Let us know how you get on with the new brakes won’t you.
    Just a pity we didn’t pin down the actual cause of the squeal, Que Sera
  • step83
    step83 Posts: 4,170

    I’m glad you’ve got a result in the end T_dog Let us know how you get on with the new brakes won’t you.
    Just a pity we didn’t pin down the actual cause of the squeal, Que Sera

    Likely a duff piston seal, even seen on a few where they are assembled in a hurry either the hose is not quite tight enough on or the bleed nipples slightly undone. both hold fluid till you use them then they weep slightly. Still seal or damaged piston (especially those white ceramic ones) are more likely going on the pattern round the back of the pad, if it was the bleed nipple or hose your would see it all over the caliper.
  • david37
    david37 Posts: 1,313
    RS785 are fantastic until theyre shite. first one then the other. cheaper than hope but theyre disposable items and since theyre on the cheaper end of Shimano mass manufacturing the quality appears to be variable.

    of all the products Ive seen from Shimano, these are up there with the worst. which is a shame because generally Shimano is in my mind a by word for peace of mind.