Disc Brake Noise

[CPD]

If your brakes squeal, what do you do about it ?. Am I right in thinking that most noise comes from contamination (grease, much etc on the disc), or is there more to it ?. Has anybody looked at using grease (copaslip is a common solution for car disc brake noise) or shims or any other solution ?. I have heard that metallic pads are more prone due to hardness which sounds likely to be correct ?. Interested ina ny comments ........... trying to learn

 

[UphillSlowly]

If your brakes squeal, what do you do about it ?. Am I right in thinking that most noise comes from contamination (grease, much etc on the disc), or is there more to it ?. Has anybody looked at using grease (copaslip is a common solution for car disc brake noise) or shims or any other solution ?. I have heard that metallic pads are more prone due to hardness which sounds likely to be correct ?. Interested ina ny comments ........... trying to learn

My understanding is that it's contamination and happens to me mid ride if roads are mucky. Now spend special attention cleaning discs and pads after such rides, but not sure if it can be prevented. Keen to hear what others say

 

[si_c]

It often is contamination, cleaning the pads and rotors is usually the best bet.

Swapping to resin pads from metallic compounds will also help, but make sure to properly clean the rotors before using new pads as any contamination will transfer.

 

[T4tomo]

If you have some cheap "supplied with the bike pads" and the issue doesn't stop with a good clean with disc brake cleaner, then get some ceramic replacement pad. That said, this time of year there is so much crap on the roads that squealing discs are just an occupational hazard.

 

[Alex321]

They will always tend to squeal when wet, but if doing it otherwise, then it is probably contamination. It can be very hard to actually get rid of that contamination without actually removing the pads to clean them and the rotors.

My lbs actually suggested putting the pads through the dishwasher!

 

[fossyant]

Mine only squeal when initially braking when wet. You've got to be careful when maintaining a bike, don't go spraying oil or silicone lube everywhere without being careful. If I've been doing a bit of maintenance, I'll usually blast the discs and pads with brake cleaner (available cheap from car motor factors - don't use rip off bike stuff). It's also good at dissolving general dirt that can get in and around the pistons and pads.

 

[roubaixtuesday]

Squealing discs are just another advantage over rim brakes, giving excellent warning to others of your deceleration.

 

[ianrauk]

Semi Metallic disc pads from Disco Brakes. These seem to be 'squeal-less' even in the wettest and dirtiest of conditions.

 

[si_c]

Semi Metallic disc pads from Disco Brakes. These seem to be 'squeal-less' even in the wettest and dirtiest of conditions.

I'd also add Noah and Theo Ceramic Pads, I've had a lot of success with these over the last couple of years. The N&T Resin pads are also quite good and quiet, but they wear out quickly as I'm a fairly big guy.

 

[ianrauk]

I'd also add Noah and Theo Ceramic Pads, I've had a lot of success with these over the last couple of years. The N&T Resin pads are also quite good and quiet, but they wear out quickly as I'm a fairly big guy.

Good stuff.
The Disco Brake pads I have last over year and many thousands of miles of commuting and touring. Even though like everything, the prices have gone up, they are still a bargain.

 

[Yellow Saddle]

My understanding is that it's contamination and happens to me mid ride if roads are mucky. Now spend special attention cleaning discs and pads after such rides, but not sure if it can be prevented. Keen to hear what others say

There are two types of disc brake friction media and the two react differently to different scenarios.
The pad and disc are two components of a friction set and the two are designed to work with each other. Mixing is not optimal.
The two systems are abrasive and adhesive. Abrasion systems use sintered metal pads and adhesive systems use resin, or as it is sometimes called, organic pads.

In abrasion friction sets, the primary friction component is created by a dead loss system where the one component grinds away at the other. Metal pads do this and they required hardened discs to cope with the wear.

In adhesive friction sets, the primary friction component is created by pad material transferring to the disc and coating it so that the friction is between two materials of the same type i.e. brake pad on brake pad. This transfer is a to-and-fro scenario with the end result of some loss through ablation of the pad material.

These two systems are not exclusive and merely dominant in one or the other. In other words, in abrasive brake systems there is some adhesion and vice versa.

New brakes have to be bedded in so that the material transfers at just the right thickness and evenness. When this balance is disturbed, either via gritty riding or contamination, the two materials no longer slide perfectly and go into an aggressive stick-slip-stick-slip mechanism that creates the noise we all so hate. The rate of this sticking and slipping is simply the frequency of the sound we hear - a couple of hundred Hz.

To cure brake noise, you have to start from scratch with new pads and new discs and bed them in properly. Understandably none of us want to do this due to the cost and hassle of the process and we look for shortcuts like brake cleaner and other potions. None work in the long term. The best fix is replace and re-bad and the second best fix is to aggressively sand the disc down so that it ends in a scratchy satin finish. Then de-grease the pads and clean them very well, and sand them flat. Then bed the brakes in again.

There is plenty of material on the web about bedding brakes. Pay attention.

Here's a good, quick education on the two friction pairs. https://www.tomorrowstechnician.com/understanding-friction-and-formulations/

Read, drink a beer, ride bike.

 

[UphillSlowly]

There are two types of disc brake friction media and the two react differently to different scenarios.
The pad and disc are two components of a friction set and the two are designed to work with each other. Mixing is not optimal.
The two systems are abrasive and adhesive. Abrasion systems use sintered metal pads and adhesive systems use resin, or as it is sometimes called, organic pads.

In abrasion friction sets, the primary friction component is created by a dead loss system where the one component grinds away at the other. Metal pads do this and they required hardened discs to cope with the wear.

In adhesive friction sets, the primary friction component is created by pad material transferring to the disc and coating it so that the friction is between two materials of the same type i.e. brake pad on brake pad. This transfer is a to-and-fro scenario with the end result of some loss through ablation of the pad material.

These two systems are not exclusive and merely dominant in one or the other. In other words, in abrasive brake systems there is some adhesion and vice versa.

New brakes have to be bedded in so that the material transfers at just the right thickness and evenness. When this balance is disturbed, either via gritty riding or contamination, the two materials no longer slide perfectly and go into an aggressive stick-slip-stick-slip mechanism that creates the noise we all so hate. The rate of this sticking and slipping is simply the frequency of the sound we hear - a couple of hundred Hz.

To cure brake noise, you have to start from scratch with new pads and new discs and bed them in properly. Understandably none of us want to do this due to the cost and hassle of the process and we look for shortcuts like brake cleaner and other potions. None work in the long term. The best fix is replace and re-bad and the second best fix is to aggressively sand the disc down so that it ends in a scratchy satin finish. Then de-grease the pads and clean them very well, and sand them flat. Then bed the brakes in again.

There is plenty of material on the web about bedding brakes. Pay attention.

Here's a good, quick education on the two friction pairs. https://www.tomorrowstechnician.com/understanding-friction-and-formulations/

Read, drink a beer, ride bike.

Very helpful thanks. Hope to try this out soon.

 

[CPD]

Great responses - thanks so much. I wonder if anyone has ever tried grease (on the back of the pad) to reduce noise ?? …….. or possibly shims, as used in the auto industry ??????

 

[C R]

Great responses - thanks so much. I wonder if anyone has ever tried grease (on the back of the pad) to reduce noise ?? …….. or possibly shims, as used in the auto industry ??????

I think I read somewhere that campagnolo use some kind of shim in their callipers to reduce the noise. Regarding the grease, I think the risk of contamination would worry me enough not to try it.

 

[Sloth]

Had new pads fitted by a bike guy, following my botched attempt to remove/resurface/refit the old pads (which had gouges in them).
Anyway, during my attempt one of the pistons came out of the front calliper, which I quickly got back in.
The guy checked and said that he was happy that the calliper was still OK and it was not now leaking following the piston popping out.
He fitted new front pads and Bobs your uncle....or so I thought.
Since getting the bike back, the front brakes just don't seem to have enough force when applied (weaker than the rear, and certainly weaker than it used to be, pre-botch) and they also make a horrible squealing sound when braking hard. I took it back and he still maintains there is no contamination of brake fluid and the the calliper does not need replacing, but yet I remain unconvinced.
Oh and yes, I did try to bed the new pads in but it did it anyway.
Will spray brake cleaner into the pads and on the disc helps? Well I tried (just the disc not the pads) but to no avail.