My shims no discs squeal like crazy and I thought new set of pads and discs would fix the matter.
It didn’t.
What other causes could there be? Should I copper grease the pad back? Why can’t I solve this. No polution on the discs. Brand new and still you can hear me coming.

caliper in perfect alignment with the disc? difficult to get right if the hose is pulling it one way or the other

I used too much copperslip one time. Just the once: it melted and flowed into the friction material. Don’t be generous.

Are all the bolts done up tight? what compound are the pads? I’ve had issues with a batch of sintered uber pads squealing. different compound has sorted it
As has been said, is everything aligned. are the disc mounts on the frame faced?

Bolts tightened to torq. Clean surfaces faced mounts too. Alignment is done either visually or by clamping the disc with the pads then tightening the bolts down. How would you go about aligning the cal opera to the disc?

I have lightly coated the back of the Pads in Copper grease, just one set so far to see if it works. Organic Pads from Shimano – New Discs also from Shimano –
Noise riders own.

Copper grease is bad news

Even someone as crap as me can get the brakes hot enough to cause the grease to migrate through the friction material and onto the contact face where it contaminates the rotors as well. It’s only a matter of time before it happens

Do not use

Apart from the advice above re alignment I generally find taking the pads out and getting everything surgically clean results smooth quiet braking. Esp the pad/piston contact area

Bugger! Done that to death with cleaning agents and cloths which is why I went with brand new pads and discs. Still It hasn’t moved yet so It could be removed, but I’m really in need of advice regarding the ‘alignment’ advice. Where and to what to you Align the caliper with? The disc, the frame how?

How would you go about aligning the cal opera to the disc?

Yeah by tightening the bolts with the lever pulled, but making sure the hose to the caliper isn’t pulling the caliper. If the hose is going around the fork or frame tightly it can pull it squint. Also check the disc isn’t being bent over to one side when brakes operated, as in one pad flexing it towards the other before the other hits.

Hayes make a tool to help align calipers, hmm the name escapes me currently.

bigjim – Member

How would you go about aligning the cal opera to the disc?

Yeah by tightening the bolts with the lever pulled, but making sure the hose to the caliper isn’t pulling the caliper. If the hose is going around the fork or frame tightly it can pull it squint. Also check the disc isn’t being bent over to one side when brakes operated, as in one pad flexing it towards the other before the other hits.
DONT do it by pulling the lever and expecting both pistons to move equally. It may work with brand new brakes, but once they are no longer new, you rarely get equal initial movement.
Take the pads out, then centre the disc in the caliper slot by eye, so its central in the slot.

Where and to what to you Align the caliper with?

As above the key is to make sure both pistons are moving equally. Once one of them starts to get lazy the other moves more and so on and so on

When both pads/piston are moving equally align the join in the caliper (where the two halves are bolted together) with the centre of the rotor (looking down between the pads)

Last problem I had with noisy Shimano discs was due to leaking seals at the caliper (which can happen if they are left idle for a long period). No matter how well you clean the pads and rotors, if the seals are leaking they will cause contamination, and consequently decreased braking performance and squealing.

ok conflicting advice. I usually work the pistons during the service with a little fluid over the seals holding one back and making the lazy piston move until they both shift, rarely does this result in two perfectly meeting, then a full clean and degrease then refit the pads using the lever clamp method.

angeldust – Member

Last problem I had with noisy Shimano discs was due to leaking seals at the caliper

Same – one replaced rotor and second set of replacement pads before I clocked what was causing it!

I used a method of checking the caliper seals using bog roll behind the pads for any trace evidence of Leaking. nothing was found.

DONT do it by pulling the lever and expecting both pistons to move equally. It may work with brand new brakes, but once they are no longer new, you rarely get equal initial movement.
Take the pads out, then centre the disc in the caliper slot by eye, so its central in the slot.

That’s why you let the pads and caliper set their position, and don’t do it by eye. If you centre it centrally by eye, and one pad moves less than the other, then one pad will contact first and bend the rotor towards the other pad.

So what happens if you have a lazy piston which means one piston wants to push the disc into the other pad rather than both pads squeezing the disc? It pushes the disc into the caliper body instead.
If you do have uneven piston movement you should be able to compensate for that by pushing the free moving piston back and pumping the lever a little to allow the lazy piston to move a bit more.

If, when you are setting the position by pulling the lever, the disc is being pushed into the caliper then you’ll hear a terrible scraping noise when the wheel spins. I’ve had uneven pistons but never one that couldn’t get the pad past the caliper body.

I’d certainly let the brake position the caliper itself anyway, to avoid these problems. Just be careful the hose isn’t pulling the caliper squint. Some discs do seem to be noisier though, I had some avid ones that had the famous avid turkey gobble no matter what you did.

My XTRs did this. Remove the rotor and degrease it, then place it in the oven with the pads at around 130-150 for 10-20 minutes and again degrease whilst still hot. You’ll be amazed how much more dirt and grease comes from the rotor. Taken the degreased pads and apply a liberal coating of Fairy (other brands may also work) to the pads and rub the two pads together vigoursly for a good few minutes and then rinse. do it a few times if it’s still looking crap.

Refit it all to your bike and bed the feckers back in.

Problem solved. I had this happen with all 3 sets of my XTRs and this fixed them…at least for a while. I’ve had to do it every 6-9months. The brakes are not losing fluid, so I’m guessing that the pads and rotor surfaces are somehow becoming contaminated when hot and it’s seeping into the structure.

Remove everything. Wet and dry the disc surface in circular motion to get rid of build up or ridges on leading edge, degrease with alcohol. Clean and lube pistons and dry off. New pads and check springs don’t foul, superstar and uberbike aren’t quite right on my zees. Copperslip can ruin seals. Reinstall disc. Use Shimano caliper adapter. Centre caliper with rotor, washer and teeny bit of grease to help centering, hold back piston opposite anything lazy. Hope have a good vid and also Pinkbike tech Tuesdays.

I only ever clean disks and pads with fine wet & dry and a clean dry cloth.

Only get a bit of a squeal if wet, soon quietens down though.

But the OP has already replaced his pads and discs.

My 2013 Avids were terrible noisy things. Moved to Shimano SLX and XT and the only time they make any noise is when they are cold and get wet. Warm them up and they’ll quieten down again. I have a set of SLX rotors and two sets of IceTech and they’re all non noisy.

I do have alignment issues sometimes from a hose pulling quite tight into an internal routed swing arm – PITA.

I very rarely clean disks or pads anymore since moving to Shimano and swap my wheels around regularly. When I do it’s with IPA alcohol and a clean rag. I spray the pad and wipe it on the rag then do it again. After the 2nd time they’re pretty clean.

I never centre them by eye. I let the brake do itself.

Wouldn’t put any copper paste near them personally.

Metal pads are noiser than organic but organic don’t like wet muddy uplift days as I found out and killed a brand new set out in a weekend. I only use finned Shimano pads and generally stick to metal all year round.

Could there be play in the hub bearings or QR not done up tight enough?

Maybe you’ve just hit the resonant frequency of the fork or something – different size rotor?

As for sticky pistons, I remove the pads, pump the brake a few times (not too much) and lube them with silicone spray, then clean it all down. No idea if this is the right thing to do but it worked with my old Avid Juicys.