Brake hum/honk while light braking?

RipGroove

RipGroove

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Very crude video attached 😂

New Galfer Pads and Magura Rotors and Deore brakes.

Both brakes work very well, lots of bite, all bedded is as they've done around 60km. The front honks (as per the video) while light braking, as soon as I heavy brake it stops. The rear is totally silent as it should be.

The front rotor has a very slight warp (even though I bought it brand new 😡), could that be the issue? Or could it be the back of the pads needs bedding in more against the pistons? I assume it's not that though as the rears are fine and obviously the fronts have been used a lot more during the 60km that they been on the bike.

It's very annoying while slowly cruising through town or traffic or just wherever. Obviously I'll buy a rotor trueing tool and try and straighten it but it's a two piece rotor so not sure how effective that will be? If that doesn't work I'll swap the front and rear rotors over and see if the noise migrates to the rear. But in the meantime, any ideas? Pretty sure everything on the front end is torqued up correctly so nothing up front should be loose other than the pads.

Video ⬇️

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skizzian said:
a rotor straightener should work with a 2 piece rotor - you won't be moving it far
Click to expand...
Awesome, I'll give that a go then, I just wondered because it's quite a sharp kink rather than like half the rotor being out of true so it'll be tricky to straighten I think.
 
RipGroove said:
Awesome, I'll give that a go then, I just wondered because it's quite a sharp kink rather than like half the rotor being out of true so it'll be tricky to straighten I think.
Click to expand...
hmm, well I'd try and get your money back first...
 
skizzian said:
hmm, well I'd try and get your money back first...
Click to expand...
I can try but obviously I've done 60 odd km's with it, no harm contacting the shop though as there's clearly no damage to it like it's been hit on anything and bent by me.
 
irie said:
If it were me I would first swap front and rear.
Click to expand...
Yep that's what I'll do, not ideal as I have a Magura speed sensor magnet in the rear rotor and the way it fits is a bit janky, it relies on a washer kind of digging itself into the aluminium housing of the magnet to hold it on so there's only a certain amount of times that it'll actually be able to be removed and refitted again. But you're right, it's absolutely the thing I need to do to see if the noise migrates to the rear.

The bike shop where I got the rotor from weren't interested which I was surprised about because when they were a smaller business they have been extremely helpful in the past. They said it's very unlikely the rotor is warped, and that probably 1 in 1000 Magura Rotors arrive with warps (buts it's definitely warped I can see it) and said that people are quick to blame noise on warped rotors. Ultimately they unofficially pointed me towards googling Magura brake noise because there were fixes online that they couldn't officially recommend. I know exactly what they were hinting at because I've had many Magura brakes in the past and used to put gaffer tape on the backs of the pads.

But again, my brakes are Deore with Galfer pads and Magura rotors so that's not the issue. Plus of course the rear is silent (and the rear rotor is running true) and the front was silent with my old Shimano rotors and pads so there's nothing else loose at the front of the bike. The only things that have changed are the pads and rotors, and the one that's warped is making the noise under light braking but silent under heavy braking so logic tells me the warp is vibrating the pads under light braking. Very annoyed because the rotor was £50 and it's clearly warped.

I'll swap the rotors over in the next few days and I'm fairly confident the noise will either move to the rear of the bike or both brakes will be quiet as potentially the rear of the bike is stiffer so will be absorb the vibration better than the front does.
 
Remove the disc and lay it on your kitchen worktop (I'm assuming that its flat and not tiled). That will clearly show how warped it is. Then take a photo and the disc to the bike shop if it's local. If not send the photo.
 
steve_sordy said:
Remove the disc and lay it on your kitchen worktop (I'm assuming that its flat and not tiled). That will clearly show how warped it is. Then take a photo and the disc to the bike shop if it's local. If not send the photo.
Click to expand...
Good idea, I did offer to send them a video of it waving around but they didn't seem interested, I guess because that wouldn't totally point to just the rotor so your idea is better, I'll send an email with both and see what they say.
 
cream said:
I would say it's rather caliper alignment problem or maybe contamination rather than a warped rotor.
Click to expand...
Definitely not contaminated, caliper seems pretty straight, hard to tell when eying it up against a warped rotor, but I'd did try to realign it initially but it made zero difference to the noise.
 
cream said:
I would say it's rather caliper alignment problem or maybe contamination rather than a warped rotor.
Click to expand...
My bike fell off the towbar bike rack and the disc landed on the rack frame. Later, in the garage, I could neither see nor feel any damage to the disc and I thought I'd got away with it. But when I spun the wheel it was touching one of the the pads and making a slight noise each rev. There was obviously a slight bend in the disc. There was no physical damage to see, no marks or burrs, raised lumps, nothing. The damage was so slight that I could not even see which brake pad was being impacted, despite shining a light behind the calliper. I put some radial felt tip marks on the disc, both sides and rotated the wheel. Some of the marks had been partially rubbed off. So now I knew which way and where to straighten the disc. I used a pair of Mole grips and got it right first time.

That was with a disc that appeared to have no warping or damage. @RipGroove says that the disc is clearly warped, so his noise must be louder and more irritating. It should show up on a flat surface.
 
Oh yeah it's totally warped , can see it clearly, noticed as soon as I fitted it to the bike. Figured it might be ok but clearly isn't, as per the video it's a loud honk rather than just pad rub.
 
Ok I'm at a complete loss now! (Video below)

Swapped the rotors over and the noise stayed at the front of the bike so that's the rotor eliminated as the cause.

With a cable tie on the front brake lever applying light pressure to the brake which frees up a hand so I can spin the wheel and touch things to feel for vibration the whole rotor vibrates and hums like crazy, the spider and the 'floating' part. The centre lock ring is brand new and a Magura part and it's the same with it at the recommended 40nm as well as 50nm.

I've tried damping certain parts with my hand to see if I can get it to stop but damping the forks, spokes, caliper and pads does absolutely nothing. Also made sure all the spokes were tight as well.

Logic tells me that as the only loose parts at the front of the bike down there are the pads, pad retaining pin, pad return spring and the floating part of the rotor but I've ruled out the rotor and the noise is still there when I apply pressure to the pads, pin and spring!! I also tried duct tape on the back of the pads which made zero difference.

Definitely not contaminated as I've had my fair share of those in the past and this is different, and of course the brake goes silent with full pressure and bits and holds very very well. Problem is probably 75% of the braking is done with medium to light pressure so my bike sounds absolutely terrible (see video below):

Any idea?!!

This is with light pressure applied to the lever:

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ha erm hum err
alignment perhaps
loosen off the caliper bolts enough for the caliper to just move and see what happens when the brakes are applied
I cleaned my Shimano 4 pot pistons last week -then centred them, then centred the caliper
but I didn't get it quite right and it honks like a goose right now at low brake pressure
I'm replacing with a Zee Caliper tomorrow - so I haven't bothered sorting it
 
it is possible you didn't get it quite right still...
you might have tightened up on the bent bit - think I'm grabbing at straws - but that's the stage you're at
might be worth doing what I said - just to see if it stops when the caliper is very slightly loose
they do twist when you torque them up
 
Very much appreciate the ideas but the rotor that's in the front is the one that was on the rear which runs very true. This could only happen to me 😂
 
I had a similar sound after a few hundred miles and did the following which resolved it.

Wear latex gloves this whole process to avoid touching the rotor and pad surfaces.

Clean the rotor very thoroughly with Brakleen. If that's not easy to get locally, use 99% isopropyl alcohol. Wipe until a paper towel or microfiber cloth comes away clean.

Lay some 100 grit sandpaper flat on a workbench, grit side up, and lightly sand your pad surfaces using a figure 8 motion. Keep sanding until the pad surface is a uniform color and texture. Try not to breathe the brake dust.

Clean the pads with Brakleen and a paper towel or microfiber cloth until there is no more visible dust on the paper towel.

Reinstall the pads and go through the full bedding process.
 
I think I'm on to something, stock headset cap on the bike was plastic and has cracked which has allowed the headset to loosen every so slightly. I found an old aluminium cap and put that on that seems to help, buuuuuut, in order for it to help I've had to do it up so tight that the bars no longer mover freely. More investigation needed as the two do seem related maybe.
 
RipGroove said:
I think I'm on to something, stock headset cap on the bike was plastic and has cracked which has allowed the headset to loosen every so slightly. I found an old aluminium cap and put that on that seems to help, buuuuuut, in order for it to help I've had to do it up so tight that the bars no longer mover freely. More investigation needed as the two do seem related maybe.
Click to expand...
Sounds doubtful to me tbh
 
skizzian said:
Sounds doubtful to me tbh
Click to expand...
It does but also the noise has reduced quite a bit after fitting a new top cap. I've ran out of time today so I'll have to have another look in morning and report back. I'm holding my judgement until I've properly investigated it 😂
 
I've just discovered the Zee caliper I bought off eBay is knackered - the hose bolt is well and truly stuck - so I will be straightening the existing caliper
 
Now is the time to start getting into the detail.
Are you sure that there is no brake pad contamination?
When you swapped discs, did you check that where the disc is bolted to the hub that it was clear and free of contaminants?
Was your original front disc actually warped? (If it was, I'm astonished that it had no impact on the rear).
Reset the caliper again. Leave the caliper bolts loose, pull the brakes and then tighten each bolt a bit at a time, keeping pressure on the the brake lever the whole time.
It's time to ensure that the disc and pads are scrupulously clean and re-sanded as @AirKuhl suggests. I would also wire wool the disc.
Is the wheel balanced and true? No wobble that you can see or feel when it spins. Any out of balance forces could act as the exciting force that creates the howl.
Remove the wheel axle, clean it and the holes it passes through and the surfaces it clamps on. Refit to the correct torque.
Try some CopperEase between the back of the pads and the pistons. It is a high temerature non-binding grease that will act to damp vibration.

I once had a rear brake howl on a Kona Dawg Supreme 2009, it had a Scandium alloy frame and top level components throughout. I tried EVERYTHING that I could think of, that the members of the MBR Forum could think of. I also contacted the Kona tech desk and it had them stumped. The bike sounded like a car horn. I was in the French Alps and coming down the hills, you could hear me for miles. I tried the local bike guys on the trails, I went to local bike shops. All they could offer was a change of pads, which lasted about a mile.
The thing that lasted longer was Swissstop Brake Silencer. It is expensive but you don't need much (I bought a 50ml aerosol). It lasted about 150-180 miles before the howl started up again. It was a temporary fix but not a cure. I even removed the entire braking system and replaced it with one from another bike and it still did it!!! I replaced all the calliper bolts with titanium instead of steel and with spring washers underneath. All to no avail. I reckon that it was the frame resonating and therefore unfixable if I couldn't locate what was causing the vibration.
In the end I dismantled the bike and sold all the parts. I never got a single complaint about brake howl from anyone.
 
To rule out contamination I'll swap the front and rear pads in the morning as the rear brake is currently silent even after swapping the rotors and the noise stayed at the front of the bike so yes I agree that I need to rule out the front pads being contaminated, if the noise moves to the back after swapping them then that gives us an answer, if it stays at the front then we've completely ruled out pads and rotorsb🤙🏻
 
We have Shimano m6120 brakes with 220mm Swissstop rotors. They work fine, dont know what a wandering bite point is. Not messing with them. Had Magura brakes on motorcycles paired with Braking rotors. Worked fine. The original brakes were some Aprilia calipers which were crap so quickly went in the bin.

When it's shit get rid and walk away and buy something else.

Contrarily, when it works don't mess or try to improve it.
 
irie said:
We have Shimano m6120 brakes with 220mm Swissstop rotors. They work fine, dont know what a wandering bite point is. Not messing with them. Had Magura brakes on motorcycles paired with Braking rotors. Worked fine. The original brakes were some Aprilia calipers which were crap so quickly went in the bin.

When it's shit get rid and walk away and buy something else.

Contrarily, when it works don't mess or try to improve it.
Click to expand...
You can have a calliper lsightly out of alignment...typical result is brake rub.
you can have some elements of the front of the bike with some slight movement..........it will not make the brake squeal
You can have a slight warp on the disc......result is brake rub

so what does cause brake squeal?? contamination or pad to rotor bed in failure...or pad to rotor bed deposit incompatible.
The latter caused by using different compound pads on the same rotor.

As a bove you best bet is to start with clean pads and rotor...meaning clean both with IPA, wet and dry/wire wool. Then re bed in the pads.It is often more difficult to fully bed in new pads on the front brake espeically if you use sintered pads, mainly because ride/bike weight is typically lighter on the front wheel than the back and fork compression can take away some of the pressure on the front brake needed. You are probably already aware of the bed in process, but to reiterate, the goal is to repeatedly apply hard pressure on the brake whilst a voiding generating too much heat.That means riding relatively slow and braking hard for a short time before releasing a little before you come to a stop..............and that needs to be done several times using front brake only.
 
Mikerb said:
You can have a calliper lsightly out of alignment...typical result is brake rub.
you can have some elements of the front of the bike with some slight movement..........it will not make the brake squeal
You can have a slight warp on the disc......result is brake rub

so what does cause brake squeal?? contamination or pad to rotor bed in failure...or pad to rotor bed deposit incompatible.
The latter caused by using different compound pads on the same rotor.

As a bove you best bet is to start with clean pads and rotor...meaning clean both with IPA, wet and dry/wire wool. Then re bed in the pads.It is often more difficult to fully bed in new pads on the front brake espeically if you use sintered pads, mainly because ride/bike weight is typically lighter on the front wheel than the back and fork compression can take away some of the pressure on the front brake needed. You are probably already aware of the bed in process, but to reiterate, the goal is to repeatedly apply hard pressure on the brake whilst a voiding generating too much heat.That means riding relatively slow and braking hard for a short time before releasing a little before you come to a stop..............and that needs to be done several times using front brake only.
Click to expand...
Well I've done everything right so far like I always do, brand new pads and rotors, wheels were taken off the bike wearing gloves so when I come to handle the pads and rotors the gloves come off and I have clean hands, I've not touched the rotor or pad surfaces with my hand or anything else, I haven't put either down on any surface other than clean paper and always with the pad surface facing upwards. I did the correct bed in procedure as I always do. The bike hasn't been washed since fitting the new pads and rotors, no liquid of any kind has touched them either, not even plain water.

The noise stayed at the front when I moved the rotor to the rear so the rotor isn't contaminated and I'm 99% sore that when I swap the pads over front to rear tomorrow that the noise will still be at the front of the bike which would totally rule out any issues with the rotors and pads and only leave the front end of the bike causing an issue somewhere.

As said earlier, all spokes on the front wheel have good tension and the wheel axle, caliper bolts and rotor centre lock are all torqued correctly. The only thing wrong with the front end was a plastic top cap that was cracked, causing the headset to be slightly loose and replacing it with an albeit ill fitting random aluminium cap I had spare drastically reduced the noise. At this stage I'm not saying that was the cause but it was definitely amplifying the noise at the very least. Hopefully I'll have some more clarity tomorrow, at the very least swapping the pads front and rear will either completely rule out pad contamination or prove pad contamination (rotor already ruled out) so that'll be a good starting point, and I'll also go get a proper top cap from my LBS.
 
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