Squeaking disc brake. Tried almost everything
 

Hi there I’ve got a squeaking front disc brake and feel like I’ve tried everything. It squeaks when I brake and particularly in cold conditions. It also has some minor vibration.
so far I’ve tried cleaning the brakes and pads with iso alcohol, specialised disc brake cleaners, replacing the pads, replacing the disc and even replacing the caliper+pads.
I recently realised when I run a rag with iso alcohol over the brake ( around it). It creates the same squeaking noise. As if it’s a resonating frequency of some kind. Has anyone ever seen this before? And any suggested fixes. I have videos but can’t seem to upload here.

Have you or anyone else visually aligned the caliper? People think they can set the caliper by grabbing the brake lever and tightening.

Visually’s a difficult adjustment. Loosen, squeeze brake lever & tighten caliper bolts. Then adjust fixed puck unless both are live.

calipers have very little to do with squeaking/squealing... the pads and discs do.

what brand, and TYPE(resin/organic?, semi metallic? Metallic?) of pads are you installing/replacing?
same info on the disc used, please.(Brand? Center lock? 6 bolt?)

also.. once contaminated, the pads MUST be replaced... no amount of chemicals will get the oil, etc. out of them.
yes, i've tried.
the most effective treatments were resurfacing the discs with 120 EMERY Paper (NOT Carpenter sandpaper), and refinishing the pads on the side of my grinding wheel, after soaking in electrical contact cleaner, then sun drying.. they still went back to squealing a day or two later.... sigh.

something i have not tried yet, on bicycle brakes..."disc quiet" pad coating... you apply it to the back of the pads... it's similar to silicone gasket stuff, RTV, but really high temp... available at any auto parts outlet.

Thanks the replies. Just to give some more details:
It started when I got a warranty replacement frame from Giant and they put my original brakes/disc on the new frame. that store then looked at it 3 times and replaced the pads first then disc+pads and both times cleaned everything well. They couldn’t find any issue and said they were “satisfied” with it but it still squeaked so I took it to another store and they first have it a thorough clean and then replaced the brake caliper as a last check.

I don’t believe it’s solely contamination as it happens even on a new set of pads after the first ride. It only happens in colder conditions (I live in Australia so it’s not ever really that cold).

they are Shimano resin pads L050A-RF.
the disc is Shimano RT-MT800-S
the bike is a TCR Advanced SL

it never happened on my bike before I got the new frame.

How are you bedding the pads?

Here is a link to a video- cleaning the disc with iso alcohol and it making a squeaking sound similar to what I get when riding and applying the brakes in colder conditions. Is this typical?

we.tl/t-2rrpSJqIlN

Basically braking really hard a few times. The guy in the store also tried to bed them in as good as possible. I’ve had so many different pads now I’ve lost count of which ones are bedded but I’m pretty sure they’ve all been given a good go.

As a shop mechanic, I disagree.

My wifes discs are quiet on her mtn bike

It’s still not a good way to adjust the calipers but it can work if you’re lucky. Visual adjustment, and there’s a knack to it, is more reliable.

Kontact, as a former shop mechanic for almost 40 years, I agree with you. Centering of the rotor in the caliper has nothing to do with a vibration problem.

I had a Specialized road bike with an unsolvable squealing front brake problem. Fortunately for the owner, the bike was under warranty. Specialized immediately pushed the problem onto Sram, and Sram, being the saints that they are, willingly took on the issue and we replaced the entire front brake system, including the lever. No solution.
Installed a front brake from the same model that we had in stock. No solution.
I then took a wheel off of a Giant road bike and put it on the Specialized and this solved the issue. The wheel was the problem, not the rotor, not the pads, not the caliper, not the fork, not any other part of the bike. It was the wheel.
Next i took a wheel off a Specialized road bike and had brake noise. I then took an aftermarket wheel of higher quality and the problem went away. At this point I informed Specialized of all this and convinced them to send out a replacement wheel set that was one level up from the stock Roval that came on the bike. This solved the issue. Something about the stock wheel was a problem. Sent it Specialized and they did who knows what with it.

This experience had me change my tune about Sram, they are in my good graces now, and it confirmed why I prefer rim brakes for my own bikes.

In my experience, this stuff is bright red. Read the directions. You put it on the pads and then let it set up for about ten minutes. You can get about a 12oz. squeeze bottle. They also sometimes have little tiny squeeze packets that have enough for one brake job.

The fact that you found a bike with a wheel resonance issue does not mean that askew calipers can't also cause squeal.

When a caliper is canted off the plane of the disc, the disc has to change shape as it passes through the pads under braking. That is more than enough to also make that contact sing. (We are talking off-parallel, not off-center.)

I don't know what is causing the OP's problem. But I have solved enough brake squeal on uncontaminated parts by carefully aligning the caliper that it is something absolutely worth checking. And the prevalence of the "hold the brake and tighten the bolt" advice is enough to make me wonder if all shop mechanics are savvy enough to avoid doing that. So I would recommend the OP puts a piece of paper on the floor and look through his brake gap to see if the pads are nice and parallel to the rotor before they buy any more stuff. You can put the paper back in the printer when you are done, so there is no cost for performing this check.

Yep, faced the brake mount using the Park tool. Nothing worked until we changed the wheel to the next better Roval model.

A bike can make noise when it is wet so sometimes after spraying with alcohol it will still squeak until it dries. I would first check proper alignment of the caliper and then make sure the brakes are bed in properly and then give us a report. Sometimes the squeezing method doesn't work. I tend to find a bit of both starting with a squeeze and visually aligning after and then alternate tightening of the bolts tends to work pretty darn well.

That isn't what I'm talking about. Talking about thr caliper being canted laterally in it's designed plane of adjustment.

Kontact, I plead ignorance here. If the mounts are faced to the axle/rotor, the caliper should be square to the rotor.

Looking straight down at a flat mount caliper in line witht the bolts, the holes in the frames are ovals to allow you to slide the caliper right or left. That also allows the caliper to be turned clockwise and ccw. That twist is what I'm. Talking about. Same with post mount, but the caliper has the oval holes.

I've seen more than one official maintenance manual outline that exact procedure for lining up the calipers. SRAM was one of the offenders. Lining up manually by eye is something I haven't seen in a maintenance manual ever. Then again it's been a few years since I read about lining up calipers. But it could be that some mechanics go with the bad info they get in tech docs because it's convenient and they can claim it's official.

But another trick on the same vein is adjusting pistons manually. Sometimes one of the pistons is a bit dominant or more protruded, which can cause the pads to twist the rotor slightly when braking. That can cause noise or be felt as vague bite point. The way to correct that is to put s small screwdriver behind the non dominant pad (not between the piston and the pad!), and push the pad towards the center whilst simultaneously slightly pulling the brake lever. This should push the dominant piston back a bit and allow a more even contact.

You're bringing up another problem that is common on used caliper - asymmetrical piston drag. I will generally pull the pads and wheel and hold the more mobile piston fully compressed and pump the other in and out a few times. Also a good time to clean and lube the pistons.

But that's different than having the caliper twisted because the rotor is too flimsy to overcome the drag of semi-tight bolts, and won't center the caliper if there is a gap under it from loose bolts.

Manuals suggest techniques that a consumer is expected to be able do with only moderate mechanical skill. But current hydraulic brakes benefit from a wide range of techniques that no manufacturer publishes. Bikes are becoming non-serviceable by amateurs.

I’m not a pro mechanic, but I’ve learned to use different methods. Squeezing the lever and then tightening the bolts is just the first/easiest thing. Sometimes it works, sometimes it doesn’t. Fine tuning by sight is definitely a process I’m familiar with. My gravel bike has been the most challenging to get drag-free, but I eventually get there. It could probably use a brake mount facing.

Kontact, thank you for the explanation, and I agree with you on that front, which is part of the setup that I took as common knowledge. The bike I am referring to was well beyond "toe-in, toe-out". Disc brake setup is simple when it goes well, but can be confounding when it goes sideways. Motor vehicle brakes are much easier because they are more consistent. Mass has advantages.

What brand? Is the rotor tightened and is the brake centered properly? Did you set the caliper with any sort of tool?