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I've been using disc brakes on MTB for 20 years now and while I might occasionally have experienced a bit of squeal occasionally after immersing the whole bike in a river, it's never really been a problem...but my gravel bike is driving me insane! The bike is a Ridley X-Trail with Ultegra 6800. Riding around in yesterday's rain was a little less listening to a cross-channel ferry motoring through the middle of a sailing regatta - HAAAAAAARRRRRRR! HAAAAAAARRRRRRRRR!
I've changed pads more often than I care to mention. I've also had them off, heated them, sanded them down and replaced, which did improve, but only for a ride or two. I've become much more careful when cleaning and re-lubing, but TBH, I've never bothered that much on the mountain bike and never had a problem.
The one thing I've not done a lot with is the rotors themselves. These are 6-bolt SRAM affairs (don't ask me why Ridley use SRAM rotors on an otherwise 100% Shimano bike!), and while I've had them off, heated them and cleaned them, I'm starting to wonder if this particular design of rotor is more susceptible to resonance and, thus, squealing. Normally, I'd have slapped on a set of Freeza rotors, but the 6-bolt configuration limits options here.
I appreciate that this is a black art, and definitely a common topic here, but I'd really appreciate any advice, be it practical suggestions on things I can do in the workshop, or links to black-magic incantations, or recommended animal sacrifices. My kids' hamster is looking nervous...
Change the rotors.
I tried changing rotors, first to something with more cut-outs (Magura Storm SL) to 'break' the film of water - didn't work.
Then to something as stiff as possible to reduce resonance (XT rotors with alloy carrier). Didn't work.
I was going to start experimenting with anti-squeel coatings (this is what Campag use on their pads) such as CRC or Liqui-Moly, but I just didn't really fancy the idea, seemed messy and offered potential for contaminating pads.
Tried anti-squeel tape behind the pads of my TRPs but it was too thick, required taking off pad adjusters to fit it.
In the end I just gave up and built a rim brake gravel bike instead with Swisstop BXP pads, I'll take the slightly increased stopping distance over screeching thanks, it's not a DH bike after all...
Good luck in your quest!
Edit: You'll no doubt be advised to 'get the rotors hot' in order to reduce squealing, but as I found out, this is surprisingly hard to do on rolling, wet, cold winter road rides where frankly you don't want to be hauling on the brakes when you don't know what might be underneath your front wheel...
Assuming the brake calipers are not leaking (it does happen) and contaminating the pads I would seriously consider fitting shimano discs, I have solved a few noisy brakes just switching from Sram-Shimano disc rotors. 6 bolt I would go RT66/Zee/SLX.
Use Shimano rotors and some new pads. That way you will eliminate all possible reasons for a squeal.
On my bikes I dont get any squeals, most likely due to me cleaning the rotors with brake cleaner each time I wash the bike and ensuring I stick the hose on the caliper to wash out any crap. I do clean my mountain bikes probably after each ride, not so my road bike. But basically you need to remove any build up of dirt / worn pad material on the rotors and ensure you dont have any leak of fluid on the pads.
Labrador worked* for me, but hamster is worth a go
*under a full moon
On my bikes I dont get any squeals, most likely due to me cleaning the rotors with brake cleaner each time I wash the bike
In my experience this doesn't work for the sort of squealing the OP describes, I have brand new Deores on brand new rotors which have frankly been cossetted to an embarassing degree, but if I'm out for a long slow ride in the rain and cold - welcome to squealy town!
My other plan was to cut sipes in the pads with a fine saw blade...
Thanks guys, and thanks for the advice.
Yes, indeed - they do stop squealing once they get warm or dry out (i.e. once you've suffered 15 seconds of ear-splitting din and got the rotors hot), but this will only last until they get damp again. Riding on the road, in a group, on a wet day when the brakes aren't getting a whole lot of use, you can be sure that they'll be shouting each and every time they are used.
Thanks for the suggestion to switch to rim brakes - I may moan about the sound, the power and modulation of discs are hard to give up, even with the associated noise. It would also mean dumping the frame and I otherwise really like the bike!
Leaking calipers are a definitely possibility. I've had this before with 6800 brakes (and, indeed, swapped to R8000 on another bike with an older, more used groupset to fix this, as well as a multitude of other issues!) I guess at some point I'll bite the bullet and swap this one to R8000 too.
Any thoughts on disc pads? I've tried a fair few sets of the (expensive!) Shimano OEM ones, both sintered and organic, as well as some cheapy ones which I'm using now (if I have to keep replacing them anyway, might as well use the cheap ones!). Interested in recommendations here. In the end, I think I'll swap the rotors too and see what difference that makes. I've tried everything else anyway.
Got to go now. Next door seems insistent on talking to me about his family dog which went missing over the weekend...
I thought the traditional SRAM howl was due to the disc resonating, and they’d changed the design to prevent it?
I can’t talk about brakes, mind you; persistent squeak on last ride turned out to be the pad spring rubbing on the disc. Again.
Thanks for the suggestion to switch to rim brakes
Sorry, hope that didn't come across as unhelpful! I circle these threads like some sort of unpleasant vulture but in truth I'm just waiting for somebody to suggest some sort of magical cure so I can enjoy the vast selection of otherwise awesome looking disc-equipped bikes.
I experimented with changing the resonant frequency of my frame by taping a lead wheel weight to it. Surprisingly it actually worked quite well, certainly took out some of the higher squealing tones, but of course I was now riding around with a heavy lead weight crudely attached to my frame!
The other thing I would have liked to experiment with is different shapes and materials of frame, but that sort of experimentation gets expensive quite quickly...
Uberbike race matrix pads get good reviews.
The disc brake squalling is multi factorial
ON a road bike I would suggest the likelihood is road grime contamination combined with cold polishing of the brake pads. Use the brakes hard every now and then rather than just gently should cure it and keep it away.
Trek did actually fit a small weight as a resconance damper device to the rear brake caliper of one of thier DH bikes, I actually saw it on Rachels bike and asked the mechanic what it was.
Use the brakes hard every now and then rather than just gently should cure it and keep it away.
I'd just like to point out that this may not be well received on a group ride
For me, with similar brakes, it needed the rotors and pads replaced. Genuine Shimano Resin Pads and new rotors fixed the issue.
Later I had the dreaded leaking calliper and nothing would fix it.
or use smaller discs?
I thought the traditional SRAM howl was due to the disc resonating, and they’d changed the design to prevent it?
Interesting. Will look into this.
Use the brakes hard every now and then rather than just gently should cure it and keep it away.
I’d just like to point out that this may not be well received on a group ride
That's putting in mildly. In fact, it's amazing how little your brakes get used on a tight, group ride. Stick in some rain, and expect to get some ribbing from your silent, rim-brake-equipped road mates :-/
Sorry, hope that didn’t come across as unhelpful! I circle these threads like some sort of unpleasant vulture but in truth I’m just waiting for somebody to suggest some sort of magical cure so I can enjoy the vast selection of otherwise awesome looking disc-equipped bikes
It's ok - not remotely unhelpful at all. Like you, I can't quite understand why I'm having so many bloody problems here, where others aren't, but it's safe to say that disc road bikes seem to be a few years back from MTB in design maturity! My son races on rim cantis with carbon rims - often another place to experience squealing - but we never have a problem and, if we do, it's nearly always because I've been a fat-handed **** on the setup and have toed the brakes in backwards by mistake!
I think I'll swap rotors and pads and see what that does. After that, it'll be new calipers.
try filing a chamfer on the leading edge of the pads. Try copaslip on the back of the pads.
Once a squeal starts then frame resonance will make it worse - but frame resonance is not the cause. the cause is the pads slipping then gripping on the disc at a high frequency
Like you, I can’t quite understand why I’m having so many bloody problems here, where others aren’t
Well this is the bit I find interesting, like others have said above, if it's to do with resonance then you have to find a way of changing the resonant frequency of your frame/fork etc. e.g lead weights!
I've put on 5kg since being off injured, so perhaps my brakes won't squeal any more as the frequency of overall system will have changed (trying to put optimistic spin on being slower and heavier...). Don't know how big a change you need to make in percentage terms to change the frequency. I always imagine riders on smaller frames probably have less of an issue.
All I know is that I'm going to continue moaning about it until manufacturers actually put some R&D into the subject 😀
resonance will only make it louder not cause it - the cause is the fast slip and grip of the pads. It could of course change it from a easily ignored noise to the howling that you hate.