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help with a squeaky disk brake

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help with a squeaky disk brake

Old 10-20-20, 03:04 PM
  #1  
benjamin163
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help with a squeaky disk brake

hello,
I just changed the fluid in my front disk brake and also changed the pads.
All is working well but the brake makes the most awful shriek when the pads engage on the disk.
It really is incredibly loud.
Is this normal for new pads? Will the noise reduce with wear? Or have I done something wrong?
All help gratefully received. Thank you.
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Old 10-20-20, 03:47 PM
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Probably failure to clean the old rotors and bed in the new pads.

https://www.bikeradar.com/advice/wor...sc-brake-pads/
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Old 10-20-20, 04:09 PM
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Originally Posted by benjamin163 View Post
hello,
I just changed the fluid in my front disk brake and also changed the pads.
Did you bed n the new pads?

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Old 10-20-20, 04:29 PM
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Contamination.

And of course this shouldn't be in GD, but should be posted in 'bicycle mechanics'.
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Old 10-20-20, 05:12 PM
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What kind of pads are you using. You mention they're new, are they different than what you had before? I switched to organic resin pads and my squeals went away. You also need to bed them in and hopefully you did a thorough cleaning of the rotor before you installed them. Good luck,
Yes, this might get more hits in Bicycle Mechanics, but the heading kinda says it all.
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Old 10-20-20, 05:58 PM
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I switched to Swiss Stop blue compound and no noise at all.
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Old 10-21-20, 02:08 AM
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Originally Posted by tyrion View Post
Who Knew???
Such a kerfuffle!
I did none of the 'bedding in' I'm afraid.
Another lesson learnt.
And I was so pleased with myself for finally getting the bleed done.
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Old 10-21-20, 02:09 AM
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Ha,
I did none of the above.
I was basking in the glory of a successful brake bleed.
A job half done and all that.
I'm off out into the rain to 'bed in'.
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Old 10-22-20, 08:58 AM
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Disc brake pads are sensitive to the angle they work at, just like rim brakes. A slightly wider clearance where the disc turns into the pad will stop the squeak.
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Old 10-22-20, 09:40 AM
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Originally Posted by rydabent View Post
Disc brake pads are sensitive to the angle they work at, just like rim brakes. A slightly wider clearance where the disc turns into the pad will stop the squeak.
I'm wondering how disc brake pads can be anything other than parallel to the rotor. And how you think a 'slightly wider clearance' will stop noise caused by contamination?
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Old 10-22-20, 01:19 PM
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As stated above, if after bedding in the new pads you're still squeaking away then you've got contaminated pads & rotors

Prior to doing anything make sure your rotor's dont say "for resin only" IF they do and you're using metallic pads, there's your problem.

Do clean the rotors as best you can, dish soap & water or rubbing alcohol. Get the pads & rotors nice & wet & try to bed in again.

If that doesn't change anything, take the pads out. Get a propane torch & torch each pad for 45 seconds. As they cool, re clean your rotor. After they cool gently sand them clean using a fresh part of sand paper for each pad.

Re bed, you should be good to go.

I've used the "torch" method more times than I remember & it saved the pads every time.
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Old 10-22-20, 01:56 PM
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You don't have to get the pads or rotors wet to bed them in properly. Just apply one set of brakes and ride as hard as you can for 50 meters. Repeat with the other set. Then you are done.

You don't have to use a torch to clean the pads. A bit of sandpaper will work (if indeed you need anything at all, which you probably don't). Unless you got brake fluid on the pads, they are probably fine.

Clean the rotors with isopropanol or ethanol and a paper towel.

Brakes do make noise in rainy conditions sometimes.
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Old 10-22-20, 06:04 PM
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I clean my pads and rotors with Acetone (nail polish remover) and then lightly sand the pads with 240 grit paper. Bed in with water (usually from my water bottle) and many short braking stops. Do not lock them up until you've finished bedding them. I should add that I only use resin pads. Good luck,
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Old 10-22-20, 06:15 PM
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One other option that I have to do every so often is to reset the caliper to the rotor. You loosen the two bolts that hold the caliper and then apply the brakes with good force. Tighten the bolts while applying the brakes. This then makes the caliper straight with the rotor.
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Old 10-24-20, 05:34 AM
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Hello all,
I can't thank you enough for all these answers.
I widened the clearance. That didn't work with the howling noise.
I've taken out the pads and have taken a picture of them and the rotor.
It looks to me like the pads are a dirty. Would you say so?
But it also looks like the pads are only engaging on the rims of the rotor.
What seems clear to me is that the rims of the rotor are full of residue from the pads and the middle isn't.
The pads seem to back this up because the coating in the middle of them hasn't been touched whereas the outer parts of the pads have been rubbed clean.
I wonder why that is happening? Can anyone enlighten me?
In the meantime I shall take your advice and clean both the pads and the rotor and try again.
Your thoughts are hugely appreciated.
And at least I'm getting a good lesson in the finer points of disk braking systems.
Ps the noise of the brake only comes as the bike comes to a standstill. The harder I pull on the lever, the more horrible the noise. Juddery too.



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Old 10-24-20, 05:35 AM
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Originally Posted by wgscott View Post
You don't have to get the pads or rotors wet to bed them in properly. Just apply one set of brakes and ride as hard as you can for 50 meters. Repeat with the other set. Then you are done.

You don't have to use a torch to clean the pads. A bit of sandpaper will work (if indeed you need anything at all, which you probably don't). Unless you got brake fluid on the pads, they are probably fine.

Clean the rotors with isopropanol or ethanol and a paper towel.

Brakes do make noise in rainy conditions sometimes.
I may well have been clumsy and got brake fluid on the pads. Do you think this will rub off naturally or do I need to get the sandpaper out?
I have posted pictures of the pads below. Do they look to you like they need a good sandpaper?
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Old 10-24-20, 08:01 AM
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Originally Posted by cxwrench View Post
I'm wondering how disc brake pads can be anything other than parallel to the rotor. And how you think a 'slightly wider clearance' will stop noise caused by contamination?
The caliper is mounted with two bolts. You can indeed affect the pad angle by shimming the calipers at those two bolts differently.
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Old 10-24-20, 08:37 AM
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Hey Benjamin, Looking at the pads, I would start by cleaning them with alcohol or acetone and then rub them over 240 grit sandpaper until all the glazing is gone and they look uniform again. You also need to clean the rotors with the same stuff because the oil has been transferred to them also. Do all that and make sure you use clean rags or paper towels so you don't just spread the oil around. With that done, use a little water and bed them in. Do not lock up the brakes or overheat them. Lots of easy rolling stops. As they bed in the noise will stop and the braking power will increase.
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Old 10-24-20, 09:03 AM
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Originally Posted by benjamin163 View Post
I may well have been clumsy and got brake fluid on the pads. Do you think this will rub off naturally or do I need to get the sandpaper out?
I have posted pictures of the pads below. Do they look to you like they need a good sandpaper?
If you got brake fluid on your pads they are ruined. No ifs ands or buts about it, they need to be replaced. They are very porous and the fluid will get all the way through however much friction material is left.
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Old 10-24-20, 09:11 AM
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benjamin163
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Originally Posted by Bigbus View Post
Hey Benjamin, Looking at the pads, I would start by cleaning them with alcohol or acetone and then rub them over 240 grit sandpaper until all the glazing is gone and they look uniform again. You also need to clean the rotors with the same stuff because the oil has been transferred to them also. Do all that and make sure you use clean rags or paper towels so you don't just spread the oil around. With that done, use a little water and bed them in. Do not lock up the brakes or overheat them. Lots of easy rolling stops. As they bed in the noise will stop and the braking power will increase.
Thanks for this. Everthing you suggested has been done and guess what? No more gut wrenching sounds!!! Thanks so much for your help and advice.
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Old 10-24-20, 09:15 AM
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Just to say, thank you everyone for the advice.
A good clean of the pads and the disk has done the trick.
I never would have thought a little dirt could make such an outrageous noise.
Thanks again.
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