Disc brake squeals when damp

paulbnix

This is my second winter bike with disc brakes. Sold the first one on because the size wasn’t correct.
Both have SRAM hydro - first Rival and current one Force.
I do remember the first bike squealing occasionally but this is far worse.

On a fairly flat ride on Saturday it wouldn’t stop squealing and there were no hills to heat the discs up.
This is with the original pads which have done about 1700 miles. As the front was on its wear limit I replaced front and rear with Disco Brakes Kevlar pads.
Out today with no rain but damp roads they are again squealing but not all the time. They are quiet after a bit of braking.

A friend suggested the original pads may have got contaminated with diesel or something.

Anyhow - any suggestions? Which pads to try? Any other frigs?

Thanks

vitesse169

Could be water on the disc being super heated when braking, more likely to be something like grit on the pads.

def_defyr

My Campy discs squeal -- well, the rear one -- when it's wet. I've looked into a bit and seems to be a combination of "they all do that" and "clean the pads with alcohol."

Oddly my front brake is totally quiet in the wet. The rear one is worst when it's damp, but in full rain seems to quiet down.

Worst case, a remedy seems to be different pads and/or rotors.

brundonbianchi

The pads and discs can’t help but get instantaneously contaminated, when you ride in wet conditions. There are some things you can do to reduce the noise, but you’ll never stop them squealing a bit.

hdow

Something to live with I'm afraid with our climate and filthy roads.

Saves on having a bell though

janwal

https://gorillabrakes.com/shop/avid-brake-pads/sram-red-22-force-22-rival-22-disc-brake-pads/
Try these semi pads from a shop in Kendal. I’ve used them for two years now on Sram hydro without any noise problems apart from a quick twitter when first applying them in wet conditions and then they are silent. I tried them after reading an MTB post recommending them. In the dry they are totally quiet. Wear fairly quickly on the front with the hills around Huddersfield ,which is not a problem as they are such a good price.
I do use them with Shimano freeza rotors though so don’t know if this makes a difference.

paulbnix

I’ve been building some new wheels for the bike and I’ve finished and fitted the rear. Whilst doing this I’ve thoroughly cleaned and sanded the rear rotor with wet & dry.

I hope to give it a go tomorrow- there’s certainly no shortage of dampness for the test.

I will order some of the gorillabrakes pads as I’ve not got any spares currently.

If the squeal is reduced I will wonder if the new hub has made any difference ??

david37

get a rim brake bike, decades of development and no squeeling.

paulbnix

david37 said:

get a rim brake bike, decades of development and no squeeling.

I have one.

itboffin

What I don’t get with my rim braked winter bike is why the squealing when the roads are wet and muddy, is it because I have my pads super close to the rims and that grinding noise ugh

roger_merriman

I have 3 bikes two MTB with hydraulic and a gravel with cable disks none squeak, beyond the first touch possibly.

Disks do seem to like being used ie reasonably hard braking at times, and if new bike possibly need bedding in.

zenpaul

It is most often that the rotors are contaminated with oil/grease, dirt.

When I clean my bike I do the rotors first - with a completely clean soapy sponge, and they are silent on my next ride (after some light braking to apply the brake pad material to the rotors).

If I don't clean the bike after a wet ride, they usually make a noise on the next ride.

brundonbianchi

itboffin said:

What I don’t get with my rim braked winter bike is why the squealing when the roads are wet and muddy, is it because I have my pads super close to the rims and that grinding noise ugh

Adjust the toe angle of the pads, job jobbed.

First.Aspect

There is a lot of magic flute around disc brakes. If they were so susceptible to contamination then they would be problematic for cars, mountain bikes etc.

The squeal for the same reasons canti's or any other brakes squeal. Give them and the rotors a clean and light roughening and start again.

paulbnix

First.Aspect said:

The squeal for the same reasons canti's or any other brakes squeal. Give them and the rotors a clean and light roughening and start again.

I don't think that is true. With rim / cantilever brakes the squeal is usually fixed by angling the pads correctly i.e. toeing in.

The disc brake squeal seems to be caused by water on the rotors. If the pads and rotors are not contaminated then this squeal lasts for a few rotations until the water is displaced. The brakes are then quiet until next doused by water.

If there is contamination then the squeal lasts a lot longer.

I am trying to determine if there is a combination of disc pad and rotor that will drastically reduce or even eliminate the temporary squeal that happens when the rotor gets wet.

First.Aspect

What do you think the squeal is? It is pads vibrating against the disc.

Why do you "toe in" rim brake pads? To stop the squeal of pads vibrating against the disc. What does toe in do? Temporarily, while the pads bed in, it promotes a smooth contact, so you don't modify the braking surface to promote further juddering (i.e. squeal).

So give the pads a good wash - dunk them in solvent if you are convinced they are like oil bearing rock - but otherwise just re-prime the surface and start the bedding in process again.

What, in your mind is "contamination"? And why does this unseen, unremovable ephemeral thing mean we all need to buy new pads if we ever go outside with them?

Let me put this in context. I have been known to be careless with WD40 and spray this on my brakes. It is a PITA, but this most mobile and low surface tension solution has never irrevocably contaminated my brake pads. Any more so than diesel and other censored I driver over or through has contaminated my car's brake pads causing me to die upside down in a hedge.

It is just technobabble.

paulbnix

First.Aspect said:

What do you think the squeal is? It is pads vibrating against the disc.

Yes it is exactly that.

First.Aspect said:

Why do you "toe in" rim brake pads? To stop the squeal of pads vibrating against the disc. What does toe in do? Temporarily, while the pads bed in, it promotes a smooth contact, so you don't modify the braking surface to promote further juddering (i.e. squeal).

This doesn't make sense.

First.Aspect said:

So give the pads a good wash - dunk them in solvent if you are convinced they are like oil bearing rock - but otherwise just re-prime the surface and start the bedding in process again.

What, in your mind is "contamination"? And why does this unseen, unremovable ephemeral thing mean we all need to buy new pads if we ever go outside with them?

Let me put this in context. I have been known to be careless with WD40 and spray this on my brakes. It is a PITA, but this most mobile and low surface tension solution has never irrevocably contaminated my brake pads. Any more so than diesel and other censored I driver over or through has contaminated my car's brake pads causing me to die upside down in a hedge.

It is just technobabble.

I agree any contamination is probably removed just as you described.

The issues I am looking at (and I wish I had not mentioned contamination) is the squeal that happens when my totally clean rotors and new pads become wet either from rain or splashes.
Can I eliminate this with suitable choice of rotor and pad?

First.Aspect

Same effect as licking your finger and running it around the rim of a wine glass. Perhaps some finesse with the brake levers?

It does make sense btw, rim brake pads are flexible so if you for them in the trailing end contacts first and then the contact area increases with pressure was the pad deforms. I used to just bevel the leading edge instead.

paulbnix

janwal said:

https://gorillabrakes.com/shop/avid-brake-pads/sram-red-22-force-22-rival-22-disc-brake-pads/

I fitted some of these yesterday. They are a bit better than the Discobrakes Kevlar ones I had before.

I still get a squeal when the rotors are wet but I can feather the braking and eliminate it sometimes.

I’ve got two completely different rotors - front is SRAM Centreline and the back is a Shimano 105 - and they both squeal.

I think I’ll accept that it is like it is now and wait for the rain to stop 😀

j_vora

Hello !

I came across this reply on VeloNews that sheds light from a different perspective on squealing disc breaks - May or may not directly answer the OP, but perhaps provides another aspect to consider in trying to resolve this issue.

May help many of us understand what else maybe happening if the brake-pad and rotors are clean and other variables have such as "embedding brake-pads" onto rotors, etc have been done and yet the squealing continues -

Head half-way to the article for this particular Q&A -

https://www.velonews.com/gear/technical-faq-tire-width-rim-fit-bottom-brackets-and-silencing-disc-brakes/


Jai

paulbnix

j_vora said:

Hello !

I came across this reply on VeloNews that sheds light from a different perspective on squealing disc breaks - May or may not directly answer the OP, but perhaps provides another aspect to consider in trying to resolve this issue.

May help many of us understand what else maybe happening if the brake-pad and rotors are clean and other variables have such as "embedding brake-pads" onto rotors, etc have been done and yet the squealing continues -

Head half-way to the article for this particular Q&A -

https://www.velonews.com/gear/technical-faq-tire-width-rim-fit-bottom-brackets-and-silencing-disc-brakes/


Jai

Thanks for that Jai but if I understand the article correctly it is describing disc brakes that squeal all the time due to frame resonance unlike mine that only squeal when wet.
In my case it happens to both front and rear which a) completely different rotors and b) carbon fork and titanium frame respectively.

I've decided to try a mod on the rear brake by sticking some tape across the back of the pads. The tape is sail repair tape and it all fits together without any pad rub on the rotor.

Watch this space

paulbnix

paulbnix said:

I've decided to try a mod on the rear brake by sticking some tape across the back of the pads. The tape is sail repair tape and it all fits together without any pad rub on the rotor.

Well that didn't work. All it did was changed the frequency of the squeal when the rear rotor became wet.

Next is to file a chamfer onto the leading edge of the rear brake pads.

Charlie_Croker

paulbnix said:

paulbnix said:

I've decided to try a mod on the rear brake by sticking some tape across the back of the pads. The tape is sail repair tape and it all fits together without any pad rub on the rotor.

Well that didn't work. All it did was changed the frequency of the squeal when the rear rotor became wet.

Next is to file a chamfer onto the leading edge of the rear brake pads.

I don't see what will be achieved, apart from reducing the braking area therefore increasing the pressure required on the remaining pad - wait a minute... that might just...

veronese68

Try sawing a groove through the middle of the material like this

Admittedly in automotive use but I was told it helped keep squealing down. Also a spot of copper grease between the back of the pad and the piston was supposed to help.

paulbnix

Looking at the picture the pads look to have a chamfer as well as a groove so I’ll try that first.

If that doesn’t work I’ll look at a groove - I’ve acquired a few partially worn pads during this exercise and there is plenty of wet weather for test purposes ☔️

webboo

If you watch one of the professional cyclocross races, just listen to the squealing as they all hit the first bend after the start. They are riding top of the range bikes maintained by professional mechanics and they shriek.

Charlie_Croker

veronese68 said:

Try sawing a groove through the middle of the material like this

The grove in automotive pads is primarily a wear indicator, but worth a try to see if it affects squealing I guess

Charlie_Croker

I’ve seen discs glowing red-hot on a car and smoking on a motorcycle and although a bicycles discs are much thinner I’ve never seen any evidence of them getting really hot.

Bicycle discs appear to be made from no more than mild steel, I wonder if tempering them would have any anti-squeal qualities

lesfirth

Charlie_Croker said:

I’ve seen discs glowing red-hot on a car and smoking on a motorcycle and although a bicycles discs are much thinner I’ve never seen any evidence of them getting really hot.

Bicycle discs appear to be made from no more than mild steel, I wonder if tempering them would have any anti-squeal qualities

I do not remember seeing a rusty brake disc on a bike. Shimano " ice" discs are a steel aluminium steel sandwich.

veronese68

Charlie_Croker said:

veronese68 said:

Try sawing a groove through the middle of the material like this

The grove in automotive pads is primarily a wear indicator, but worth a try to see if it affects squealing I guess

Could be, I was told it helped get rid of brake dust and residue so keeping noise down.
I was also told a chamfer stops the leading edge catching so makes for a more progressive application. This is more applicable to drum brakes on old motorcycles though.
Saying all that I just accept that bicycle discs squeal on first application in the wet, then go quiet for the next few hundred yards. But they work and if some poor sap gas just stepped in front of you they save you having to shout a warning

zest28

Charlie_Croker said:

I’ve seen discs glowing red-hot on a car and smoking on a motorcycle and although a bicycles discs are much thinner I’ve never seen any evidence of them getting really hot.

Bicycle discs appear to be made from no more than mild steel, I wonder if tempering them would have any anti-squeal qualities

I dare you touch my discs after mountain biking with your bare fingers.