Ok, I give up. Help me Obi-wans, you’re my only hope.

My back disc brake squeals, and it’s doing my nut in. It’s worst when the bike’s under load, and goes EE – EE – EE – EE largely in time with my pedalling (one EE per revolution), but it intermittently does it when coasting or even pushing the thing too. I’ve found that if I apply gentle pressure to the rear brake lever it goes silent, but I can’t spend the rest of my life riding the brakes. The bike’s 12 months old nearly, and it’s done it pretty much as long as I can remember.

I’ve cleaned the disc (with IPA spray and compressed air) which made no difference. I’ve had the pads out and tried sanding them with wet&dry to remove any contaminants, and in desperation I’ve even ended up taking a Turboflame to the pad surfaces, but it still persists if sounding like I’ve got a pair of shagging mice in my hub.

I’m thinking that the solution here is just to bit the bullet and buy new pads, but I was wondering if there’s anything else I could try first?

Cheers.

sticky pistons?

Warped rotor?

Sorry’
Sticky pistons or misaligned mount or bent rotor ime
Sorry sorry!
Edit, this happened to me on an old frame, the mount was welded on slightly wonky, a quick facing at the LBS sorted it
Sorry again 😀

Cleaning things wont’ make any difference. The pads are supposed to be clear of the rotor when you’re not braking.

If they aren’t, then there are a few points to consider:

1) The calliper must be centred on the rotor. Adjust it with shims or the bolts depending on what you have. It is theoretically possible (see below) to slacken the bolts, squeeze the lever and then tighten them but this is problematic – you can do it by eye also.

2) If you do this and it still rubs, one of the pistons might not be moving properly, or at all. Both sides should move the same amount when you squeeze.

3) The rotor could be bent so it’s rubbing in one spot. It’s really easy to bend them even with light pressure, and they can be bent back with fingers easily enough. I have to do this regularly since I hate rubbing brakes. You’ll never get it perfect but you can get it good enough not to rub.

4) If none of the above work you might need to face your calliper mounts. See your LBS

If you’ve been running it with 1, 2, or 4 above then you’ve probably worn the pads unevenly so you may need to do your adjustment with fresh pads.

Cheers all. Sorry(!) for the delay in replying, got sidetracked.

1) – centred on the rotor in respect to what, disc running parallel through the brake you mean? Should be able to sight that, I think.

2) – again, possible to check visibly? Squeeze and make sure they both move?

3) – I’m fairly sure I’ve checked this, but it’d be consistent with the squeaking so I’ll check again. I didn’t realise it was hand-bendable in a sensible manner.

4) – not much I can add to that.

I’ll have a fettle and see what I come up with. Thanks for the feedback.

Was going to write a long reply but molgrips +1 will suffice 🙂

There’s a video on the Hopetech site that shows caliper cetralising, principles are the same for all calipers but the actual method of adjustment may vary

http://www.hopetech.com/page.aspx?itemID=SPG219

Push the pads back and centre it then, also, hold one pad with a tyre lever and (gently) squeeze the lever to get the other piston to move out, not too much or the piston will pop out, and repeat both sides until they move freely, its easier to Take the caliper off to do that btw,
Worth a trip too your LBS to get the mount faced, it’s pretty cheap and quick to do and eliminates that from the problem as well

Sorry 😀

Shush. q-:

Cheers both.

Wifes bike did this a while back. Turned out to be suspension pivot bearings.

Turned out to be suspension pivot bearings.

Thought #1, “I bloody hope not, that sounds expensive.”

Thought #2, “Hang on a minute, I have a hardtail.”

(-:

Markie > you know, I suspected it might be hamsters all along.

Ok, I’ve had another look with the comments here in mind.

I had a proper look at it in good light and it seems that when the brake lever is released, the innermost pad moves away from the disc but the outer one stays touching (or almost touching) the rotor.

So tonight I took the wheel out again. I separated the pads with a large dull screwdriver (like I did last time), squeezed the brake lever whilst watching what was going on, and couldn’t see that one was sticking particularly.

I opened and closed them a couple of times to work the piston, then put the wheel back in.

Now. On the upside, this appears to have cured it. Releasing the lever now has both pads moving away from the rotor, and the squealing seems to have stopped. It still makes a noise under braking sometimes, but TBH I’m not that fussed about that.

However. The braking action’s changed too. Whereas before, the lever moved, well, normally, now there’s a lot more travel before the brake starts to bite; I’m hitting my knuckle with the lever, and could probably get it all the way down to the grip if I tried hard enough. Releasing the lever moves the pads much further away from the rotor than before.

WTF is going on here? It can’t be an airlock surely, it’s a sealed system and I’ve not changed anything. I’m assuming it’s something to do with the auto-adjusting system, but I’m not 100% on how that actually works.

The brakes are Elixir 4’s, if that helps.

Are the pads worn unevenly? Try new pads, one may be fatter than the other, so that now you’ve pushed them back in, one still has to move further because the pad is thinner
I’d fit new pads and give it a bleed,

They don’t look unevenly worn, but I guess it’s hard to tell by eye. Far as I can tell, they’re both moving equally.

I’m just perplexed as to how it could suddenly need bleeding. It didn’t five minutes earlier.

You have to take em out to tell really, if they are worn uneven after you push the piston back in the self centring bit sets em up uneven again cos one pads thinner than the other, try pumping the lever a bit and ziptieing the lever back to the bars overnight, a lot of brakes feel Squashy after the pistons have been pushed back

Probably doesn’t need bleeding. By pushing the pistons back in, the worn pads are now further away from the rotor.

Try taking the wheel out and squeezing the lever once or twice, then replacing the wheel. Check and repeat, but don’t go too far otherwise there will be no clearance and you’ll get a lot of rubbing again.

I’ll have a play. Ta.

Noob question – there’s no issue with me doing this with the bike upside-down is there? I don’t have a stand or anything clever, it doesn’t need gravity to auto-adjust correctly or anything?

If you had any air in the reservoir you might have pumped it into the brake line I guess…

I think, fundamentally, I’m expecting too much of the autoadjust. Either that or it’s buggered in some ephemeral way that’s beyond my comprehension. Are they normally this fiddly to tweak?

Dropped the wheel out again, closed up the brake and put it back, back to the original problem. Which is good, from a certain point of view. Now I can’t seem to get it not to drag on the rotor no matter what I do.

I’m going to call it for tonight, I need my beauty sleep. Thanks for everything thus far though.

Could be glazed pads. Take them out and rub with sandpaper, then bed them in again (you did bed them in didnt you?)

Tracker’s on the right line, i’m guessing that you had the bike upside down when you did the work to it, and pumped air that would otherwise be sat at the top of the reservoir into the system.They’re never completely air free when they come from the factory, if you have free moving pistons a good bleed will produce a solid lever with minimum travel.

From the OP,

I’ve had the pads out and tried sanding them with wet&dry to remove any contaminants,

I don’t think I did anything specific to ‘bed them in,’ but if they’re not bedded in after being on the bike for 12 months, I think perhaps they never will be…!

Fixed it.

1) The calliper must be centred on the rotor. Adjust it with shims or the bolts depending on what you have. It is theoretically possible (see below) to slacken the bolts, squeeze the lever and then tighten them but this is problematic – you can do it by eye also.

It was this. Slackened off the bolts, wrapped an elastic band (well, actually, a hair band) (the thing you tie hair back with, not Motley Crue) around the brake lever, then nipped it all up again.

It still doesn’t sound exactly right, which I’m guessing is due to uneven wear; however, it’s shut the hell up for the first time in months. I dragged it round Trawden today and nary a murmur.

So, thank you to all that replied. *does the dance of joy*

So, thank

Sorry, I missed this.

i’m guessing that you had the bike upside down when you did the work to it, and pumped air that would otherwise be sat at the top of the reservoir into the system.

I did, so that would fill in the remaining blank in what was going on. That’s ace, thankyou.

I had this on mine. Tried EVERYTHING to figure it out. Ended up being the bits inside the rear hub (cones?) were slightly loose so the wheel was a billionth of a degree off vertical with every left-foot pedal stroke. It was enough for the dreaded EE-EE-EE-EE-EE-EE-EE-EE-EE-JESUS-WHEN-WILL-IT-STOP-EE-EE-EE-EE.

About 5 minutes tinkering about and tightening up and it’s never happened since.

Hm, that’s worrying. Maybe I’ve now got a misaligned caliper to match my misaligned wheel…

Symptoms were exactly that, it’s like Chinese water torture, drives you insane. It was a toss-up which was going to happen first, me throwing the damn thing into a ravine, or my mates throwing me down one.