Disc brake squealing

jozi

I had a problem where my front brakes became completely useless recently, My guess the rotor/pads got contaminated and caused a squealing noise when braking and pretty much made the brake useless.

A few weeks ago I finally got a chance to fit new pads, I made sure the rotor was clean by cleaning it with a degreaser and a scotchs pad as well as using disc brake cleaner on the disc and also cleaning the caliper before fitting it all together with new pads.

After a bit of bad weather last week (about 2-3 days after fitting new pads) the front brakes started to squeal again and just like last time there is some bite before the squealing begins to get load enough to be unbearable. Like last time it will get worse over time and ill lose my front brake stopping power again.

Anyone any experience in resolving this? Can the rotor be lose or the caliper or what would cause this to happen again after fitting new pads and cleaning everything?

Cee-Jay-Cee

Is it possible you have a leak? The brake fluid is contaminating the pads and causing the and squeal and poor braking.

arybvtcw0eolkf

Did you use copper grease on the back of the pad, the metal plate?.

Drop out the new pads, clean the caliper and metal and apply a tiny film of copper grease on the metal part of the pad.

jozi

Regarding a leak, I don't think so, I still have enough pressure in the lever. I'll look into it though.

It's not that I lose braking power due to a lack of force, it's more because the pads just become rubbish. They start to squeal, loudly, before there's good bite from the pads.

I didn't think that copper grease would work, besides copper grease will make the rubber seals in the piston soft and over time cause it to fail and get dust in the piston and it will corrode. For this reason I rather not use it on my bike (or car), a non petroleum based grease might work but it's so right in there I don't want to risk contaminating the pads

Whatwicklow

Don't put copper grease near the pads.

Put the rotors and pads in the oven for 20 mins on a high heat. After they cool hit then all with clean sand paper - the pads, if conaminated might recover. The disk with plenty of sanding will.

It's squealing because some of the old contaminated pad material is laid down on the disk

run_Forrest_run

Whatwicklow wrote: »

Don't put copper grease near the pads.

why not? That's what you would do for brake pads on a car, same principle surely?

Would a bike shop do the oven thing??

Pigeon Reaper

Copper grease on the back of a pad is fine. It's a high temp grease designed for this type of use. My brakes have bee squealing recently due to the road salt getting onto them. They sound like a pig being fired out of a cannon with a megaphone attached.

jozi

I've read about burning the pads to get rid of the contamination but I think I like the idea of the oven better. Not sure how to get the rotor removed, it's a shimano hub/rotor/caliper, looks like the same locking ring as on the rear sprocket (which I don't have).

As far as I'm aware copper grease is petroleum based, petroleum based greases soften rubber leading to it degrading over time. The correct grease for near rubber would be red rubber grease.

---edit---

My squealing is also accompanied by a reduction in braking performance, at stand still pulling the front brake and pushing the bike will let it slip through the caliper, it's not holding the disc still like my read brakes do.

Cee-Jay-Cee

Have you the correct type pad for the discs your using? The discs on my MTB state 'use resin pads only' I don't think it would make much difference if I used sintered pads but maybe it does.

jozi

I got Shimano pads for that particular calliper, I can't remember if they were sintered or organic. It's only the front though, rear has no issues what so ever.

A slight little bit of play in the headset or lose disc wouldn't cause it to squeal? I should also probably have added the squealing is accompanied by slight vibration also

Pigeon Reaper

jozi wrote: »

As far as I'm aware copper grease is petroleum based, petroleum based greases soften rubber leading to it degrading over time. The correct grease for near rubber would be red rubber grease.

Copper grease shouldn't be anywhere near rubber if it's on the back of the disk brake pads. It's only for the contact between the piston surface and pad. If it's on rubber you're doing something wrong.

The performance drop off indicates contamination.

youtheman

I have disc brakes on my current steed.  My observations are as follows:
1. the discs are so powerful that they put a large load on the front fork and will quickly highlight a loose headset.  So any vibration under braking you might possibly need to tighten it.
2. from time to time they just squeak.  Doesn't particularly bother me, in fact it gives me good reassurance that they are working.
3. when I replaced the pads recently I had to 'zero them' by loosening the mounting bolts, pulling the lever and then retightening them while keeping the lever pulled.  You might not have to do this, just spin the wheel first and look for some binding or possibly a rubbing noise.
4. all the literature highlights that you must not contaminate the pads when replacing (even oil off your hand).  I doubt if putting copper grease would be 'couture'.
5. mine have large 'heat sinks' fitted to the pads.  Don't know what they are made of, but not sure if they would take kindly to being 'oven baked!.

arybvtcw0eolkf

Whatwicklow wrote: »

Don't put copper grease near the pads.

Put the rotors and pads in the oven for 20 mins on a high heat. After they cool hit then all with clean sand paper - the pads, if conaminated might recover. The disk with plenty of sanding will.

It's squealing because some of the old contaminated pad material is laid down on the disk

Where did you get that from?.

I've never heard or seen anything like it.

OP, drop the pads out. You can buy brake caliper cleaner in Halfords (if you REALLY want to give your calipers a good clean). Clean out the calipers, a very fine film of copper grease on the metal back on your pads and you'll be good to go.

The squealing is usually just caused by tiny vibrations between the pads and the calipers, some times brake dust can cause this but its usually just the metal pad backing on the metal piston causing a vibration & noise.

Or you could try that oven thing, lets know how that worked out.

Whatwicklow

Copper grease is used with car pads to stop things siezing together over a prolonged time period- not a problem on a mtb.

A brand new set of pads can be all but ruined with a tiny amount of grease - why put it anywhere near then?

The oven / plumbers torch is used to evaporate some contamination. . As I said - It helps, it might not fix. Heating and sanding the disk will also help.

Edit-mtb caliper should be cleaned with soapy water, brake cleaner (akin to carb cleaner) should be reserved for the disk.

Whatwicklow

Would a bike shop do the oven thing??[/quote]

Doubtful- probably just drop in new pads and bleed brakes

Big Eejit

To my understanding, sintered pads will squeal in wet weather. Indeed, mine squeal. I consider squealing a good thing - To me, it means my pads are clean. If you can't live with the noise (or the social embarrassment), try organic pads - they won't squeal... but they will wear out faster.

Either that or oil them (the pads). Oil fixes sqeaks and squeals

jozi

I don't mind squealing but this is coupled with vibration and when this happens is like the pads slip and I lose breaking performance.

They still work up to the point where the vibrations start and braking performance decreases as the noise gets louder and it gets loud enough to frighten anyone.

I never had this issue with my previous bike and that was much more neglected throughout the 4 years or so that I had it

AndrewJRenko

I could have written the OP's post myself, except for the bits about maintaining the bike himself. I left it into the LBS in November for a winter service. The brakes had been fairly squeaky beforehand. They changed both sets of pads and said they had to change the disc on the front, as it had some oil on it, which seemed fairly strange.
Within 2 or 3 days, the squeaking was back on the front, loud enough to turn heads. It can help when you're coming up to a set of lights with people around, but it's a bit silly really.

Lumen

I had quite a bit of squealing on my hydro road discs on the first set of pads (stock Shimano ice tech). I wore them down to the metal and had Penny Farthing replace them with whatever cheapo pads they had in stock, not the finned ice-tech ones. Since then not a single squeal whatever the weather.

arybvtcw0eolkf

run_Forrest_run wrote: »

Would a bike shop do the oven thing??

Maybe on April 1st.

AndrewJRenko

Both brakes are very, very squeaky when I start off. I've had dogs barking at me coming down the hill in my estate several mornings this week. The back brake seems to ease off once I get going - not sure is it temperature or damp or whatever?

Cee-Jay-Cee

AndrewJRenko wrote: »

Both brakes are very, very squeaky when I start off. I've had dogs barking at me coming down the hill in my estate several mornings this week. The back brake seems to ease off once I get going - not sure is it temperature or damp or whatever?

If the brake is squeaking while not braking then the calliper isn't aligned/centred correctly on the disc. Loosen the two Allen nuts holding the calliper in place. Pull the brake lever and tighten the bolts incrementally while holding the brake lever, this should centre the calliper.

AndrewJRenko

Cee-Jay-Cee wrote: »

AndrewJRenko wrote: »

Both brakes are very, very squeaky when I start off. I've had dogs barking at me coming down the hill in my estate several mornings this week. The back brake seems to ease off once I get going - not sure is it temperature or damp or whatever?

If the brake is squeaking while not braking then the calliper isn't aligned/centred correctly on the disc. Loosen the two Allen nuts holding the calliper in place. Pull the brake lever and tighten the bolts incrementally while holding the brake lever, this should centre the calliper.

Sorry if I was unclear, but no, they only squeak while braking - but much more so when starting off on a journey.

jozi

Cee-Jay-Cee wrote: »

If the brake is squeaking while not braking then the calliper isn't aligned/centred correctly on the disc. Loosen the two Allen nuts holding the calliper in place. Pull the brake lever and tighten the bolts incrementally while holding the brake lever, this should centre the calliper.

Guy in the bike shop mentioned this to me a few days ago. I haven't had a chance to do it yet, want to clean the disc and lightly sand down the pads before I realign the caliper.

AndrewJRenko

So the lads in the LBS bled the front brake, which seems to have sorted the squeaking. They explained that if the fluid was somehow contaminated, you get uneven, fluttering pressure on the pads which leads to the squeaking. I no longer have random strangers shouting WD40 at me at traffic lights.

jozi

Might be worth a shot! Not long after changing pads the squealing was back with the first bit of rain.

I spoke with a guy in town who said it might not be aligned properly.

I just bought new pads, will clean the caliper and disc again, sand the disc a little, bleed brakes (did notice a little spongyness lately), refit it properly and align the pads to the disc by looking through the pads/caliper with a sheet of paper for guidance and try get the caliper perfectly aligned.

nordicb

As long as copper grease doesn't touch rubber things, it should be ok.
Greases that do not attack rubber, plastic explicitly state this usually, otherwise I wouldn't put it near rubber.

I get squeaky brakes now and then, degreaser nor brake cleaner help, however wiping with the dish washing liquid eliminates the squeak completely and bite also improves, always worked for me...

Alek

wiping with the dish washing liquid

Wiping the rotors? Undiluted?

nordicb

Alek wrote: »

Wiping the rotors? Undiluted?

Yes, rotors, just a drop of liquid on a piece of damp cloth or tissue. I spin the wheel so the foam gets onto pads as well. Apologies for not being more specific.

Alek

Cheers, I'll give it a go with my notoriously squealy Hy/Rds :-)

John_Rambo

Hi Josi. I'm not tooled up for this malarky so my local bike shop took the rotors and pads off my wheels, blow-torched the oil off them, treated them, cleaned them and adjusted whatever needed to be adjusted and tightened for €16.

magicbastarder

AndrewJRenko wrote: »

Both brakes are very, very squeaky when I start off. I've had dogs barking at me coming down the hill in my estate several mornings this week. The back brake seems to ease off once I get going - not sure is it temperature or damp or whatever?

mine will squeal a bit when wet, but no more than a couple of seconds braking is enough to evaporate the water off and the squealing disappears.