Intermittent Zinging Rotor Sound

[GrandPaBrogan]

My rotors are dead straight, callipers perfectly aligned, pads are new and have been broken-in correctly and are spaced-out evenly either side of the rotor. Rotors have never had any oil on them, no marred scarring of any sort from trapped sand silica particles. Brakes are powerful and stop on a dime... silent in the wet or dry (no squeaking or honking).

BUT every now and then (usually after a bump but not always) I'd get an intermittent zinging rasping sound from the front brakes. Kinda like the sound it could make (I speculate) if one of the pads lifted off it's piston and is glancing ever so lightly against the side of the rotor... or perhaps the fork LOWERS (left slider) gets twisted but takes a moment or two to straighten out again?

Definitely not the rear brake because the sound is still there when I engage that. And yes, definitely the front because it goes away when I use the front brake - but then it returns straight after. Sometimes tapping the front brake lever gets rid of it, sometimes not - but eventually it goes away as mysteriously as it appeared (I can't recreate it in my workshop).

I have two full suspension eMTBs, I'm the first owner since brand new. Both bikes have front thru-axles, one with 180mm rotors and the other with 203mm rotors - different brand hydraulic brakes (one is 2 piston and the other is 4 piston) and have different forks - and they both do it.

Does this ever happen to any of your bikes? Anyone figured out a fix from real life experience?

 

[khorn]

Check your front wheel bearings, what you are describing sounds exactly like a bearing with a little play in it.

Karsten

 

[congerball]

Look carefully on the inside of the Caliper (the bit nearest the rotor) my rotor would very slightly catch the caliper if I braked heavy or put my weight over the front causing a “tinging” sound, I could see where it was catching as some of the black paint had warn away to reveal bare metal (very minimal but enough to notice) so I filed a bit extra away....this immediately fixed my problem and the noise disappeared.

 

[GrandPaBrogan]

Check your front wheel bearings, what you are describing sounds exactly like a bearing with a little play in it.
Karsten

You're right!

It took a bit of trial and error but this appears to be the case. It wasn't possible to simply push the hub from side to side in the workshop to confirm this. The hub needed to be under normal steering side loads and spinning while riding the bike, before it would move. Now this hub is on a brand new bike, so I know the bearings aren't shot. The most likely scenario (unless the new bearing are defective) is that the internal tubular spacer in between the bearings is a smidgeon too long (thousands of an inch). So the bearing races aren't fully seated on the stepped bearing bores of the hub. I was finally able to meticulously re-align the front brake caliper so that the rotor would just miss the pads on either side of the movement throw. I still get the rasping 'zing' but it's very faint now and very seldom.

At some point I may disassemble the hub and machine one end face of the spacer to shorten it... but better to leave it for now as the bike is still under warranty... in case it's more serious than a simple production tolerance issue.

Thanks for the tip! I wouldn't have looked in that direction otherwise.

 

[GrandPaBrogan]

Check your front wheel bearings, what you are describing sounds exactly like a bearing with a little play in it.
Karsten

Just an update Karsten... it wasn't the bearings after all on this occasion - even though the symptoms appeared to be that way (sometimes the rotor would be closer to the outer pad, but then sometimes the rotor would be closer to the inner pad).

When I picked up my brand new bike from my LBS, I asked for the brakes to be switched to what I'm used to (right brake lever to rear brake). To my surprise they did it right then and there - by just swapping over the hose ends at the levers. They said they do it like this all the time and that there's no need to do a bleed. The levers didn't feel spongy so I presumed you can do that with modern brakes.

After closely checking the hub and finding that it had no bearing play, I suspected the brake swap may have something to do with it. The only thing I can think of was that there may be air bubbles in the line that compress to nothing under braking, but then expands again after - so the brake pads don't retract back as much. I ordered a bleed kit and did it myself to confirm my suspicions. Yep, air bubbles in the front brake line where zinging was bad... no air bubbles in the rear brake line where it hardly zings.

The front brake issue was also compounded by fork flex. With the bike upside down (my feet on the handlebars to keep it from moving), when I turn the wheel itself left and right I can see that the rotor would move side to side in the gap between the two brake pads. This is what made me think it was the bearings because it would rest at a random spot within that gap. So I had to take that rotor play into consideration when realigning the caliper back onto the fork mounts. To be fair, on other forks with less flex, the hose swap without bleed may not have been an issue - the brakes were strong and not spongy.

Now that the pads retracting properly - small amounts - but that's all it took to get rid of the zinging. Mystery solved.

 

[GrandPaBrogan]

Mystery solved?
Well not quite... this saga continued some more, but hopefully I've nailed it on the head - finally!

Everything was fine, but then after a 10km ride the zinging started again! That was when I suspected that the rotors could be the culprit.

Just so happen I had a pair of brand new 203mm Avid rotors - spares from a previous bike build project. So I tried it on the front first... no zing! I could somewhat vaguely hear the rotor lightly rub against the pads every now and then - BUT it was near silent and didn't sound like two scimitar sabres glancing against each other in an epic sword fight.

So what gives? I only spotted the difference when I compared the two rotors. The stock rotors that came with my bike are Tektro 203s on the right (pic below). They only have 8 spokes whereas the Avid rotors on the left have 12 spokes. That may have something to do with the Tektro rotors having the tendency to 'ping and rattle' easily. There's not enough spokes to arrest any resonance.

As far as the rotor randomly changing positions within the gap between the brake pads, the only thing I can think of is that besides only being 8, those spokes have a curved shape making them longer and susceptible to flexing. I suspect that when the outer ring gets real hot from braking it expands - and then contracts when it cools down. The whole rotor could then be warping in and out of a 'dished' shape. I'm just guessing, but smaller 180mm or 165mm equivalents of this same rotor design may not have this issue.

Thought I'd write my findings for other Tektro brake owners out there who may be experiencing this same problem.

 

[Drewf]

Thank you for posting this thread about your disc brake ping/zing sounds because you really helped me. I just bought a Trek Rail 5 and it came with this exact same Tektro 203mm rotors and the zinging pinging sounds were driving me crazy. I tried realigning everything and the noise would still come back. Then I found your thread and I just bought a set of Avid rotors...new rotors on the way. Thanks!

 

[urastus]

Do you guys have one of those fork shaped springs that hold the pads in place? I have the same zinging noise (awesome description for what it is), and just assumed it was this spring. I shall remove it one day and spread it out a bit (or straighten it, or use a spare from previous pad replacements). I have all shimano.

 

[GrandPaBrogan]

Do you guys have one of those fork shaped springs that hold the pads in place? I have the same zinging noise (awesome description for what it is), and just assumed it was this spring. I shall remove it one day and spread it out a bit (or straighten it, or use a spare from previous pad replacements). I have all shimano.

Yes I do.

This spring prevents the pads from flopping closer to each other when you have to remove your wheels (and the rotor along with it). They also keep the brake pads pressed against the caliper pistons and away from the rotor while in operation. You are right, if the spring has NOT been installed (or has lost its strength) the pads could randomly flop and rub against the rotor.

However, if the caliper pistons themselves aren't retracting adequately, this spring is not strong enough to pry the pads and pistons apart - and away from the rotor surfaces. It's the piston inside the brake lever master cylinder (has a strong return spring) that pulls the brake fluid inside the brake line, which in turn 'sucks' the caliper pistons apart. If there are air bubbles inside the brake line, the air gaps will compress (disappear) when braking - the master cylinder piston is pushing the fluid. But when the brake lever is released, this air will expand again and prevent the fluid from sucking the caliper pistons apart as much. Besides making the brakes feel spongy, air in the system will also leave a smaller gap between the pads and rotor. This alone shouldn't cause the rotors to 'zing' on other systems, but with the Tektro Orion4F brakes with matching 203mm rotors, it appears to be a contributing factor.

 

[urastus]

Yes I do.

This spring prevents the pads from flopping closer to each other when you have to remove your wheels (and the rotor along with it). They also keep the brake pads pressed against the caliper pistons and away from the rotor while in operation. You are right, if the spring has NOT been installed (or has lost its strength) the pads could randomly flop and rub against the rotor.

However, if the caliper pistons themselves aren't retracting adequately, this spring is not strong enough to pry the pads and pistons apart - and away from the rotor surfaces. It's the piston inside the brake lever master cylinder (has a strong return spring) that pulls the brake fluid inside the brake line, which in turn 'sucks' the caliper pistons apart. If there are air bubbles inside the brake line, the air gaps will compress (disappear) when braking - the master cylinder piston is pushing the fluid. But when the brake lever is released, this air will expand again and prevent the fluid from sucking the caliper pistons apart as much. Besides making the brakes feel spongy, air in the system will also leave a smaller gap between the pads and rotor. This alone shouldn't cause the rotors to 'zing' on other systems, but with the Tektro Orion4F brakes with matching 203mm rotors, it appears to be a contributing factor.

Ok, yours must sound more solid. My sound is like a loose zinging What I was getting at is not the pistons or pads or anything else - just that spring. Imagine if it isn't expanding and holding the pads like it should. The noise to me sounds like the spring itself. Might be worth just trying to remove that spring and spread it a bit, or not? Read your post again - it looks like you solved your problem. I'll leave this up still, because I suspect the spring on mine, and it might help someone else. I've had a similar noise in the past when the pads were worn.

 

[GrandPaBrogan]

Ok, yours must sound more solid. My sound is like a loose zinging What I was getting at is not the pistons or pads or anything else - just that spring. Imagine if it isn't expanding and holding the pads like it should. The noise to me sounds like the spring itself. Might be worth just trying to remove that spring and spread it a bit, or not?

Nothing to loose. Just take if off, spread it out a bit and put it back and see what happens. I’m not sure if you can buy just that spring on its own if you needed one, but I’ve seen replacement pads that come with a new spring included. ??

 

[urastus]

Nothing to loose. Just take if off, spread it out a bit and put it back and see what happens. I’m not sure if you can buy just that spring on its own if you needed one, but I’ve seen replacement pads that come with a new spring included. ??

I've always kept the springs when fitting new pads. And the split pins, if I get new ones. No idea why . I know it's easy - I just assumed that's what it was and wasn't worried. It has done it since new. I always pick up each end and spin the wheel, before a ride and all is good. Just on bumpy downhills (which they all are) when I hear it. I want to make the front tubeless, so I'll check it out then

 

[R120]

Some aftermarket pad brands supply stronger retaining springs which help keep the distance.

 

[GrandPaBrogan]

Thank you for posting this thread about your disc brake ping/zing sounds because you really helped me. I just bought a Trek Rail 5 and it came with this exact same Tektro 203mm rotors and the zinging pinging sounds were driving me crazy. I tried realigning everything and the noise would still come back. Then I found your thread and I just bought a set of Avid rotors...new rotors on the way. Thanks!

After the swap, if you still hear a dull rotor rub (it won’t be that annoying zinging sound), there’s a good chance you may have air in your brake lines.

You don’t need to bleed your system to get rid of the air. Just BURP the master cylinder...

 

[Akiwi]

Thanks for sharing that. My last bike had that zingy sound. I never found the cause. I recently bought 2 new cubes. One has Magura mt7 brakes with 12 spokes and it doesn't using. My Wife has Shimano also with 12 spokes and the zinging drives her crazy. I'll try that with the burping.

 

[Herder000]

Have you tried it yet Akiwi? I have the same problem with my Shimano BR-MT520 brakes. I have bought a new rotor, the same type stupidily, and even the new one moves side to side as it goes through the pads so is fractionally warped. Looking around it seems larger rotors suffer more, mine are 203mm, 12 spoke RT66s and the zinging is driving me insane! Mine is worse at 15mph. My hub looks ok, there is no play in it. If I tug the wheel rim/tyre to the side the I can make it touch either pad but then I can do that on all my other bikes. I just don’t think the pads are retracting far enough. Let me know if you find a solution. I may try yet another rotor. I read somewhere the ones with different material centres are less prone to warping, don’t know if that’s true or not.

 

[Akiwi]

Have you tried it yet Akiwi? I have the same problem with my Shimano BR-MT520 brakes. I have bought a new rotor, the same type stupidily, and even the new one moves side to side as it goes through the pads so is fractionally warped. Looking around it seems larger rotors suffer more, mine are 203mm, 12 spoke RT66s and the zinging is driving me insane! Mine is worse at 15mph. My hub looks ok, there is no play in it. If I tug the wheel rim/tyre to the side the I can make it touch either pad but then I can do that on all my other bikes. I just don’t think the pads are retracting far enough. Let me know if you find a solution. I may try yet another rotor. I read somewhere the ones with different material centres are less prone to warping, don’t know if that’s true or not.

I burped the brakes the other day, but we haven't been out on a ride yet, so I can't say if it helped or not.

 

[urastus]

I often burp my brakes because bleeding for me is useless. I also find I have to burp pretty often, like one brake once a week; so each brake every 120km?

I finally took the pad spring out, spread it a bit wider, and no zing

 

[Akiwi]

I often burp my brakes because bleeding for me is useless. I also find I have to burp pretty often, like one brake once a week; so each brake every 120km?

I finally took the pad spring out, spread it a bit wider, and no zing

The Burping helped, but didn't eliminate the problem completely.
That comment with the spring I saw on another thread... I'll have to try that.

 

[Herder000]

I've noticed that my disc moves side to side as the wheel goes round. I've bought a brand new disc and it still wobbled. I then swapped it with the front which I could see was definitely not warped and when on the back it moves side to side (wobbled). Therefore on mine at least, the rear hub must be slightly out of alignment. I'm not sure what the tolerance on these things normally is but for me it seems to be causing the problem. The wheel is tight and there is no play in the hub either.

 

[urastus]

I've noticed that my disc moves side to side as the wheel goes round. I've bought a brand new disc and it still wobbled. I then swapped it with the front which I could see was definitely not warped and when on the back it moves side to side (wobbled). Therefore on mine at least, the rear hub must be slightly out of alignment. I'm not sure what the tolerance on these things normally is but for me it seems to be causing the problem. The wheel is tight and there is no play in the hub either.

if it is out of warranty, or you want to try and fix it, consider this: the rotor is fixed to the hub. According to you the rotor is not buckled but is simply showing that the hub is buckled or warped. Because rotor and hub are fixed together, if you gently straighten the rotor as per normal, everything should be OK. You'll still have a slightly wonky hub, of course.

I have an ancient, cheap, heavy mtb that I bought when I was starting. I used it to practice things, like running down stairs and riding off platforms to a flat drop - stuff like that. So my rear hub is wonky through some heavy hits. It isn't worth replacing, so I live with a tiny bit of movement in the bearings and have straightened the wheel and rotor as I normally would. It has been like that for years now.

 

[urastus]

I've noticed that my disc moves side to side as the wheel goes round. I've bought a brand new disc and it still wobbled. I then swapped it with the front which I could see was definitely not warped and when on the back it moves side to side (wobbled). Therefore on mine at least, the rear hub must be slightly out of alignment. I'm not sure what the tolerance on these things normally is but for me it seems to be causing the problem. The wheel is tight and there is no play in the hub either.

I only burp when one of the brakes gets spongy or the lever gets closer to the bar as the pads wear. I always assumed the spring was the cause of my zing

 

[Herder000]

I was thinking of putting a very very thin washer behind a couple of the bolts to straighten it out but I think that might be too much. I'm waiting for the kit to burp it before the next stage

 

[Supratad]

I get this zing but only at speeds above 18 or so. Reading the above made me think that maybe, could the disc moving at speed past the pads create an area of lower air pressure and pull the pads in at one end?

 

[Timmoh]

if it is out of warranty, or you want to try and fix it, consider this: the rotor is fixed to the hub. According to you the rotor is not buckled but is simply showing that the hub is buckled or warped. Because rotor and hub are fixed together, if you gently straighten the rotor as per normal, everything should be OK. You'll still have a slightly wonky hub, of course.

I have an ancient, cheap, heavy mtb that I bought when I was starting. I used it to practice things, like running down stairs and riding off platforms to a flat drop - stuff like that. So my rear hub is wonky through some heavy hits. It isn't worth replacing, so I live with a tiny bit of movement in the bearings and have straightened the wheel and rotor as I normally would. It has been like that for years now.

I've noticed that my disc moves side to side as the wheel goes round. I've bought a brand new disc and it still wobbled. I then swapped it with the front which I could see was definitely not warped and when on the back it moves side to side (wobbled). Therefore on mine at least, the rear hub must be slightly out of alignment. I'm not sure what the tolerance on these things normally is but for me it seems to be causing the problem. The wheel is tight and there is no play in the hub either.

Have you checked to see if the framebmounting surface the caliper sits on is "flat/square" to the rotor?
I ask this as this ping/sound was on my Sons bike - appearing after every ride. I would loosen and retighten, using the old appliance of the lever to seat the pads on the disk for squareness and tighten, but it kept coming back.
When I loosened the caliper and applied slight lever pressure, I noticed the caliper slightly canting/tipping/kicking to one side (if looking from the rear of the bike, it would kick slightly left at the top of the caliper as the piston deployed) . Therefore as the pads would touch, the top of the right pad and bottom of the left would be very close on setting and contact first with the slightest ride abuse due to close tolerances, so to speak. You would not notice this usually as you just pull the lever and tighten when adjusting.
In closer inspection, obviously the mounting surface on the frame had not been machined at 90 degrees to the caliper mounting (wheel was true and set properly).
I could not faff with taking it back during the lockdown so just "set" it by eye from above-this worked a treat and is just a case of evening the visable gap.
Just adding this possible fix to the post as best look at simple stuff first before swinging the big spanners and spurting bleed kits get you swearing ??.
Cheers........

 

[Herder000]

There has already been swearing and waving big spanners and hammers!
But all suggestions are more than welcome, mainly because I sound like a cat with a bell on its collar as I ride down the road
One interesting thing is when I lean forwards and take as much weight as possible off the rear wheel it seems to almost stop. Any suggestions about how I can put weight on it, ride at 15mph and watch the back brake at the same time gratefully received...

 

[Timmoh]

There has already been swearing and waving big spanners and hammers!
But all suggestions are more than welcome, mainly because I sound like a cat with a bell on its collar as I ride down the road
One interesting thing is when I lean forwards and take as much weight as possible off the rear wheel it seems to almost stop. Any suggestions about how I can put weight on it, ride at 15mph and watch the back brake at the same time gratefully received...
[/QUOTE
1.Go Pro set up if you/know someone who has one? (tape it on). Expensive and trusting option.
2. A Turbo trainer/rolling road-you can the ride while someone videos with phone (and good lighting). Best option.
3. You hang your missus/kid of the back and upsidedown with phone camera ?. Not best option.
Just a few ideas.........

 

[Herder000]

I like number 3 the best
I have a turbo trainer but is doesn't fit onto this bike unfortunately. I'm still hoping that "burping" it will give me fractionally more clearance and will cure it...

 

[Akiwi]

Aaaaaa Haaaaaaa!!! I think I found the problem!!
I am pretty sure it was the Spring. But not because it wasn't tensioned enough. It wasn't parallel, so one of the side arms was not sitting flat on the brake pad and was hanging over the edge a bit. I think this was occasionally contacting the disk and making the Zing Zing metal on metal noise.
I used a pair of long nose Pliers and bent it all straight.
Just did a quick test, and it was silent!!!
Only real test is when we do a longer tour. But there was a polished bit on the spring clip which was probably where it was rubbing.
I'll keep you informed if it has fixed it.

 

[Aitrui]

I have Zee brakes with Icetech rotors. I replaced the rear rotor with not Ice-tech one , the zinging started immediately.Escpecially when I turned or leaning with the bike (no play in the rear wheel hub). I tried everything, different pads, springs etc... Bought an Ice-tech rotor, zinging is gone. I think the Ice tech rotors are much stiffer, so if you hit them with the pads occasionally, they wouldn't make this annoying sound.