TimothyH

Shimano hydraulics with RT86 six bolt rotors on a gravel bike.

The wheels went in for service. The rotors were reinstalled and wheels put back in service and now the front brake squeals terribly under hard braking. Super loud.

Rotors were again cleaned with alcohol and the metal pads replaced with resin pads as a test but no change.

What should I do next?


-Tim-

Larry77

I would make sure to "set" the brakes, can see many videos on it. I've noticed sometimes that new pads and rotors can squeal until you get them worn in a little. I've also had to sand down my pads a little to get stubborn grime off of them, seems to help.

dsbrantjr

I would try cleaning the rotors and pads again with a solvent brake cleaner such as CRC Brakleen. Alcohol is not a particularly good cleaner for grease.

cpach

My guess would be the rotors weren't cleaned very well. I would use fine grit sandpaper followed up with finish line speed degreaser or similar serious solvent and disposable shop rags. In this case I'd probably also clean the pads--if they are only secondarily contaminated from not-quite-clean rotors you can usually clean them up. What you should do next is bring it back in to the shop--they should be responsible for sorting this out if they contaminated the pads/rotors during service.

TimothyH

CRC is what I use but some people get offended when it is suggested to use anything but alcohol. Easier just to say alcohol and avoid the potential argument. The rotors were wiped with CRC but I'll do a more thorough job.


I'd probably start with a fine crocus cloth before sandpaper, just enough to break through the shine, but your point is well taken.

This bike has never seen the inside of a shop apart from buying the frame and taking the wheels to my wheelbuilder for service. Again, your point is understood and I'm grateful.


-Tim-

fietsbob

I cured it by dropping the stock pads for Kool Stop organic compound replacements..


post here apparently.. have a bike shop to consult? I cannot work on your bike for you from here.

you bed in the new pads with a lot of gently modulated stops or just grab them aggressively?






....

trailangel

Watch the movie DELIVERANCE

DrIsotope

Somebody at the shop got something on your rotor. Go for a ride in the rain. For the first 20 minutes of wet riding my brakes honk like enraged geese. Then they are utterly silent, and stay that way.

Trying to lazily bleed my front brake on one occasion, I got one good sized drip of silicone on the rotor. After wiping everything down with Brakleen, the brake performed well enough, but continued to make horrifying noises. Wetsanded the rotor and pads with 400 grit and all was well. Still running that same rotor, +10k miles.

Cyclist0108

Two suggestions:

1. Don't use the passive voice.

2. Try adjusting the alignment of the caliper. Assuming the pads and rotors are clean of contaminants, this I have found is almost always the culprit. (I suppose it could also be a bent rotor, or 'mistakes were made' when putting it back on, but misalignment with respect the the caliper is my best guess.)

TimothyH

I'm not asking you to work on my bike.

If you don't want to give advice or questions irritate you that much then click the little red X at the top of the window and do something else. No one is forcing you to be here.


-Tim-

xenologer

Go for a nice muddy ride offroad in the rain and get everything dirty.

Mud breaks in everything nicely.

TimothyH

Update: fixed.

Backing plates on the pad were cleaned with CRC Brakleen to remove any potential contaminants.

360 grit sandpaper was laid flat on a table and the pads were lightly sanded using a figure 8 motion. I tried break through the surface to fresh friction material below.

The rotor was left on the bike and scuffed with the same sandpaper as best as could be done - not too aggressive but just enough to remove much of the shine. Brakleen was again used.

Result: good as new.

As an aside, the bike was ridden through rain, mud and snow in the hopes it would get better but it did not. I appreciate those who gave advice out of a sincere desire to help.


-Tim-

shelbyfv

Good you are no longer squealing, some of Ned's friends or their descendants may still be in the area.

TimothyH

Update.

Squeal came back and pretty quickly too.

I had been washing the bike with Zymol car wash soap just because I have it handy and use it on my cars quite a bit. It dawned on me that Zymol contains lots of wax and oils and so I cleaned the rotor obsessively with alcohol until the rag showed zero residue. The old pads were discarded.

It was proclaimed good last time only to start again and so I'll stop short of saying it is fixed but the squeal hasn't come back so far.


-Tim-

redlude97

While contamination could be the source of the issue, continuing to clean the rotor if there isn't contamination is the wrong approach. Break in actually involves transferring pad material evenly to the rotor. If this doesn't happen then the rotor will drag at different rates around the rotor that usually causes the squealing. For me the easiest way to do this is to take it down a descent without coming to a stop with multiple hard braking efforts. If you keep cleaning then you are starting over each time and have to follow the break in again

MBurke

I was having some of the same issues with my front disc brake and I replaced my pad (front only) with a organic pad. I know they won't last as long as others but its the front one so I'm not to worried about that.
It did fix the squealing noise and has bee good for the last year.

I have always used alcohol wipes but would like to try the Brake Klean suggested here. Someone said disposable shop rags....I have a box of the Blue Disposable shop rags here. Would they be ok to use or is there
a certain kind of shop towels to use ? Ones that would be Free from all contaminates ??

Thanks

TimothyH

What you describe is called "Bedding" the pads.

Art's Cyclery Blog » Ask a Mechanic | Bedding In New Disc Brake Pads

It has to be done with clean rotors. I cleaned the rotor once before installing the new pad. Sorry if I didn't make that clear and should have used the world thoroughly instead of obsessively.


-Tim-

redlude97

Did you bed them in after this most recent cleaning?

TimothyH

Yes, cleaned the rotor thoroughly, replaced the pads and rode around the neighborhood hills bedding in the pads.

Time will tell but it has been OK so far.

I'm not going to use car wash soap on it.

redlude97

On bikes I use Dawn, helps with road grime and grease that car soaps aren't really designed for since they need to not strip wax.

menkar

I couldn't get rid of my disc brake squeal no matter how much bedding in, cleaning, and aligning I did. They might quiet down but if I touched them wrong the squeal was back.

What worked for me is what works on cars: High temperature disc brake grease is designed to be used where the piston contacts the back of the pad and where the leading edge of the pad contacts the caliper housing. It damps high frequency vibrations at these mechanical interfaces that makes the squeal. I bought some Permatex Silicone Ceramic Extreme disc brake grease and with Q-tips I carefully applied a thin layer of it to the pistons and to the caliper surfaces where the leading edges of the pads make contact (obviously avoid any contamination of the braking surfaces with this stuff). The squeal went away completely and hasn't come back since I put it on four months ago.

The grease is sold for the exact purpose of fixing squealing discs (on cars).

TimothyH

I've used CRC disk brake anti-squeal spray and it helped for a short while. The Permatex product sounds interesting and I will give it a look.

Happy to report however, that the front did not squeal on a 60 mile ride Saturday. I purposely left the squealing rear pads on, mostly because they are new but also as a control. I'll change them out down the road (pun) if the front continues to remain quiet.


-Tim-

Troul 

Parts cleaner works well for rotor pad & caliper decontamination. Careful to not spray the tire, any seals, & painted surfaces.