Why’s my front brake howling?

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  • Why’s my front brake howling?
  • PJay
    Member

    I’ve been riding my Swift (as a slightly portly gravel bike) for about a year with an MRP Rock Solid carbon/aluminium fork. A few weeks back I swapped this fork out for a set of Singular’s own Swift forks and ever since have acquired a howling front brake (the rotor was cleaned and new pads installed in case anything got contaminated during the swap over, but without success).

    The thing is, it’s quite specific. The brakes seem fine in normal use, but at the bottom of a long road descent (coming out of the Mendips) I get 3 or 4 banshee like howls (with fairly gentle application of the brake) before everything settles down again (possibly heat related?). The brakes are old SLX M765s bought in January 2016 and are running Shimano resin pads; the rotor is a SRAM Centerline 180mm. The front calliper was previously fitted post mount via an 180mm adapter and now sits on an IS-PM 180mm adapter on the Swift forks; there doesn’t seem to be any lack of power & everything’s tightened up correctly (and the rotor’s on the right way around).

    I did wonder about leaky seals so applied the brake hard 15-20 times, then held the lever back hard for a while with the bike static (assuming that this would force the issue); there was no squealing initially but then the brakes howled coming down a couple of much shorter descent (where they’d not howled before).

    I’m a bit at a loss as to what to try; if it is leaky seals (perhaps the fork change was coincidental) I’ll need new callipers but I’m low income & don’t really want spend if it isn’t going to solve the problem (I’d want to reuse the levers and have been looking at newer Deores).

    Any thoughts?

    Premier Icon Daffy
    Subscriber

    It sounds like leaky seals to me. None of my 3 sets of Shimanos ever felt bad at the lever….well maybe the initial pull every once in a while, but not spongey, buy they all howled and they all lacked power until the howling had stopped.

    Premier Icon DezB
    Subscriber

    Just put a brand new XT caliper on my old Yeti for my son and nothing would stop it honking like a peahen having it’s eggs stolen (trust me on that). Except, buying some cheap Clark’s pads off CRC and fitting them. Not only did they work better than the XT finned ones, but they made nonoise.

    PJay
    Member

    So it could be seals then? Perhaps it’s nothing to do with the fork change after all; Would Deore M6000s give similar performance; I don’t think I need 4 pots?

    philjunior
    Member

    I’m not saying it *isn’t* leaky seals, but have you tried putting the other fork back on?

    Automotive brakes are heavily optimised to avoid squealing, the bike approach of just bolt a load of stuff together and hope for the best leaves a high possibility of resonances.

    Also I would’ve thought that, if anything, a long road descent would heat things up enough to burn off any leaking oil.

    Might be worth trying different pads to see- I had some that got squeally when hot and found the bog standard shimanos worked better and didn’t squeal, someone else has found different (with a different brand) but it could work (for the record I stopped using Clarks when a set of pads didn’t actually fit in my caliper, but if you’re fitting them at home this isn’t such an issue).

    Premier Icon epicyclo
    Subscriber

    I wonder if it’s actually fork flex under brakes exacerbating the tendency.

    Premier Icon joebristol
    Subscriber

    Surely try the old fork on and see what it does? That’ll rule out either the new fork being the issue or your brakes.

    PJay
    Member

    And if it is the new fork, what’s likely to be the solution?

    It’s an odd one certainly. The howling isn’t during the descent, but at the bottom, on the flat and at relatively slow speed, a few applications of the brake and it goes; it doesn’t howl under similar braking conditions without the prior descent – the only difference I can see would be the temperature of the rotor. Previously it only made this sort of noise in the wet. Sincere working the brake hard to try out the leaking theory it’s howled more readily. For reference, the steel forks seem a little stiffer than the carbon.

    steve_b77
    Member

    Does it only happen at the bottom of long, assuming brake drag free, descents?

    Does it happen every time in this situation?

    If so I’d say that the brakes are simply going from being cold to warm / hot very quickly and producing the noise, much akin to when you initially brake on a wet ride, you get the noise, the brakes warm up a bit, the noise goes.

    It won’t be the seals as they’d be bad and get worse and worse as the oil builds up a fine film on the pads and rotor, eventually rendering them useless.

    simonloco
    Member

    Glazed discs or pads?!
    Try roughing them up with some wet & dry & clean again before refitting

    Premier Icon zippykona
    Subscriber

    Except, buying some cheap Clark’s pads off CRC and fitting them

    Organic or sintered?

    PJay
    Member

    Does it only happen at the bottom of long, assuming brake drag free, descents?

    Does it happen every time in this situation?

    Has happened ever ride with the Swift forks but never (despite numerous times on the same descent) with the MRP Rock Solid using the same calliper & rotor. As of yesterday the brake has seemed a bit more howly.

    I may need to try the old fork again, although if it turns out to be the Swift fork I’m clueless as to how to resolve it; I’ve also got a different 180mm rotor I could try (Shimano RT66 I think). I’ll have a look to see if I can spot any leakage (the brakes are pretty old anyway).

    It might be an optical illusion, but the calliper lots slightly more upright, relative to the rotor, with the Swift forks (correct adapter though).

    PJay
    Member

    Okay, so it’s been a while but I finally got around to re-fitting the carbon fork after continuing to get loud howling from the front rotor with the Singular Swift forks. I didn’t clean the rotor or change the pads, it was just a straight fork swap and calliper alignment.

    I’ve ridden the same loop but try as I might the front brake has been howl free. I’m now completely befuddled!

    I’ve been in touch with Sam at Singular by email and he’s not come across this before. Sam did suggest that having the mount faced might be worth a try, but even if it’s a tad messy there’s a fair bit of adjustment available at the adapter/calliper interface; I had the rotor spinning clear of the pads and rub free on the Swift forks.

    I’m not clear on tolerances with mounts & adapter so did wonder whether they might be a slight difference in alignment of the pads relative to the rotor with the two forks & perhaps some issues with previous wear (although it’s a fairly new rotor).

    As far as I’m aware I’ve got the correct PM-IS adapter for my 180mm rotor and everything was torqued up correctly on the Swift forks.

    For now the carbon forks are staying put (I bought the Swift forks as spares as straight steerer forks will be increasingly rare & the next batch of Swift forks will be for tapered steerers) and life’s to short to be faffing about with this for now, but when the carbon forks need replacing I’ll be re-visiting the Swift forks.

    So, what’s going on. Pics below for folk to tell me I’ve done something stoopid or got the wrong adapter.

    Premier Icon Andy R
    Subscriber

    I presume that you’ve tried getting the rotor really hot with a succession of hard stops downhill and then throwing some dirty, gritty water over it and then hard-stop it again until it’s really hot.
    It usually seems to work for me.

    Edit * Or it’s just something to do with the different resonant frequency of the Swift forks compared to the others.
    The Swift forks will have the proper 55mm offset and I’ll bet the others don’t so for that reason alone I’d try to solve it.

    qwerty
    Member

    I thought that seals barked, not howled.

    Premier Icon kcal
    Subscriber

    random thoughts:
    a/ try the copaslip on back of pads trick
    b/ vary position of brakes/mounts by using shim washers
    c/ check the fork / headset interface is all fine and dandy – just might be the fork needs bedding in (though you’d think the swap to other fork would have same behaviour)

    PJay
    Member

    The Swift forks will have the proper 55mm offset and I’ll bet the others don’t so for that reason alone I’d try to solve it.

    Is that a big deal then? They are the 55mm offset forks (designed for the version of the Swift frame I have) and a full 11mm more than the Rock Solids; however (and I’m happy to admit to being a skill less pootler) I can’t say I noticed, they certainly were an “oooh it felt like a whole new bike” experience.

    They are lovely forks though but I’m still clueless as where to start getting the howling under control.

    Premier Icon nixie
    Subscriber

    IS mount fork? Definitely get it faced if is not. It won’t hurt the fork and will make it way easier to set the brakes up. You can get howl if one pad contacts the rotor ever so slightly earlier than the other. If your near Southampton you can use my facing tool.

    PJay
    Member

    That’s a kind offer, thank you; unfortunately it’d be too far but I do appreciate the offer.

    I’ll look at getting the IS mount faced, although I can’t say that I’ve needed to before, the Swift has an IS mount at the rear (as have all my previous frames) that I’ve had no issue with (160mm rotor) and I’ve run an 180mm rotor on a steel fork with an unfaced IS mount too (Orange F8) but it should help eliminate one possibility. I could always try another disc as well.

    scotroutes
    Member

    You might achieve the same effect as a facing tool simply by removing any paint from the area where the adapter contacts the fork. A sharp knife would likely work.

    Premier Icon nixie
    Subscriber

    @scotroutes the main thing the facing tool does is make sure the two holes are parallel. Just removing the paint will not achieve this. In the case of my surly big dummy fork they were not even close. IIRC I removed the best part of 1mm from one and just the paint from the other.

    @Pjay I’ve also used plenty just fine without facing. However if you consider something like a suspension fork there is a better chance of that being closer to parallel in the casting than a tab welded onto a tube like many steel forks (i.e. more room for error when being attached).

    scotroutes
    Member

    @scotroutes the main thing the facing tool does is make sure the two holes are parallel. Just removing the paint will not achieve this. In the case of my surly big dummy fork they were not even close. IIRC I removed the best part of 1mm from one and just the paint from the other.

    Yep, I agree. But in this case removing the paint might be all that is required. It’s a cheap/easy thing to try in order to rule it out.

    Premier Icon Andy R
    Subscriber

    Is that a big deal then? They are the 55mm offset forks (designed for the version of the Swift frame I have) and a full 11mm more than the Rock Solids;

    I always attributed the superb handling of the Singular Hummingbird to the fact that it used forks with more than “normal” offset (in other words, 55mm).
    Certainly better handling than bikes with similar head angles but with forks that had offsets of around 38-43mm.
    I imagine it was the same for the Swift. Both the rigid forks for the Stooge and Jeff Jones’ forks have similar amounts of offset and both are
    acclaimed as good handling bikes, so there’s probably something in it…

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