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  1. #1
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    Eliminating brake moan / groan?

    My girlfriend and I have the same brake set... Avid Elixir CR, but she's been noticing a loud "groaning" sound under a certain amount of pressure on the rear brake lever (so loud that it also seems to vibrate the frame and everything). I tried it out and get the same results... about 50% braking power is when it happens. Any idea on how I can eliminate this? The brake is very powerful, so I don't think it has any effect on that... it's just really annoying to her (and would be to me). Is this something to do with the pads, or the rotor? I checked the rotor and it seems to be about 99% "true". Also, the rotor probably has only 15 rides on it... and all of them fairly light (she's a beginner rider).

    Any ideas are appreciated.

  2. #2
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    I would try sanding the brake pads with a 200 grit sandpaper. That has worked for me. Depending on the severity you might need to sand the rotor as well. Just a light sanding on both sides of the rotor will do the trick. I would try just the pads first as that is a quick check. Hope this helps.

  3. #3
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    Quote Originally Posted by McKraut
    My girlfriend and I have the same brake set... Avid Elixir CR, but she's been noticing a loud "groaning" sound under a certain amount of pressure on the rear brake lever (so loud that it also seems to vibrate the frame and everything). I tried it out and get the same results... about 50% braking power is when it happens. Any idea on how I can eliminate this? The brake is very powerful, so I don't think it has any effect on that... it's just really annoying to her (and would be to me). Is this something to do with the pads, or the rotor? I checked the rotor and it seems to be about 99% "true". Also, the rotor probably has only 15 rides on it... and all of them fairly light (she's a beginner rider).

    Any ideas are appreciated.
    Is her bike a Stumpjumper? I think that there is a thread in the Spech section about it.

  4. #4
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    Quote Originally Posted by rzozaya1969
    Is her bike a Stumpjumper? I think that there is a thread in the Spech section about it.
    Nope...it's a Motobecane Fantom Pro DS... it's a loud/powerful enough groan that it actually seems to shake/vibrate through the frame linkages...

  5. #5
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    Quote Originally Posted by McKraut
    Nope...it's a Motobecane Fantom Pro DS... it's a loud/powerful enough groan that it actually seems to shake/vibrate through the frame linkages...
    I think that it might be similar, I think that Elixirs have some problems on some setup/bike models.

    I think that one of the solutions was to replace rotors, but I'm not sure about it.

  6. #6
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    Quote Originally Posted by rzozaya1969
    I think that it might be similar, I think that Elixirs have some problems on some setup/bike models.

    I think that one of the solutions was to replace rotors, but I'm not sure about it.
    weird... i have the exact same brakes as her and haven't had any issues so far... would there be any point to swapping the rear rotors on our bikes and seeing if i encounter the same thing? seems like this would be a simple fix though... maybe i'll also try the sandpaper like was suggested if i get time and see if that does anything.

  7. #7
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    Quote Originally Posted by McKraut
    weird... i have the exact same brakes as her and haven't had any issues so far... would there be any point to swapping the rear rotors on our bikes and seeing if i encounter the same thing? seems like this would be a simple fix though... maybe i'll also try the sandpaper like was suggested if i get time and see if that does anything.
    I think that I would do any or both of the options first, they cost you nothing but a little time.

    Do you both have the same bike model? If it's different, and swapping rotors and sanding them don't work, maybe you could try a different rotor than those included on the brakes. But I'm just guessing, hopefully swapping them will work.

  8. #8
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    I read somewhere that a rider was having this issue and went with 1 organic pad and 1 sintered pad in each caliper. Don't know if it actually works, may be worth a try. I have a set of Elixir R's and haven't had any issues yet. Let us know what you try and if it works.
    Cheers!
    Oldest daughter doesn't ride, she fights MMA.

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  10. #10
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    Coat the back of the pads with disc quiet. Then blast the calipers and pads with brake cleaner. Break in, enjoy.

  11. #11
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    I sanded my rotors lightly and sanded the pads until I could see the entire surface was being sanded flat. Then I cleaned the rotors with brake cleaner. They squeaked at first but after a few hard stops it seems to have gone away.

  12. #12
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    Quote Originally Posted by mbrick
    I sanded my rotors lightly and sanded the pads until I could see the entire surface was being sanded flat. Then I cleaned the rotors with brake cleaner. They squeaked at first but after a few hard stops it seems to have gone away.

    Anytime the rotors get wet, like after washing the bike, touch them up with brake cleaner. Has worked for me, and i maintain a few sets of hydros.

  13. #13
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    that is actually not always a great idea and kind of a last resort, as it can gum up the pistons in a bike brake and make them sticky. plus it burns away from there pretty quickly and becomes innefective. Ive used it between brake adapter and frame, and beween rotor and hub,(to dampen vibration) and had good results.

    Quote Originally Posted by bing!
    Coat the back of the pads with disc quiet. Then blast the calipers and pads with brake cleaner. Break in, enjoy.

  14. #14
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    Generally, there are two kinds of problems common to disc brakes. They are vibration and squeal, and while they may be related, I feel they may require different solutions.

    You didn't state what rotors you are using, but I might guess you are equipped with one of the Avid cleansweep patterns. If so, I found one of my bikes exhibited considerable vibration in rear braking with these rotors, but completely smooth braking in the front. It appeared the the rear set vibrated at a frequency set by the disc pads passing over the relief slots in the rotors. It seems very peculiar that the response could be so different in front and rear, both using the same rotors, calipers, and pads.

    With that in mind, I tried quite a few different rotors in the rear setup with varying results. In general, I found most of the six spoke rotors exhibited more vibration tendency that those with 8, 11, or 12 spoke patterns, and that less aggressive relief patterns in the rotor were helpful.

    I got the best results with the Alligator 160 wavy pattern that is available from Pricepoint for a very reasonable 9.95 each. this rotor has eliminated vibration on this bike, and does not squeal at all with the Cool Stop organic pads I use with it. This rotor still has fair size relief holes, and seems to dissipate heat very well.

  15. #15
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    Quote Originally Posted by dwyooaj
    that is actually not always a great idea and kind of a last resort, as it can gum up the pistons in a bike brake and make them sticky. plus it burns away from there pretty quickly and becomes innefective. Ive used it between brake adapter and frame, and beween rotor and hub,(to dampen vibration) and had good results.
    I can only speak from experience and it has worked well from me.

    The disc quiet takes care of the low frequency vibration and groans. It dampens the pads from vibrating against the piston and thus the caliper. Does it burn away, my in-the-pants vibrations never came back, on two different bikes.

    The brake cleaner addresses the high frequency vibrations (squealing and grittiness). This washes out contaminants that causes vibrations between the pad surface and the rotors.

    Breaking it down, the rotors squeal, the frame groans. Quite simple really.

    The last resort should always be to buy a new brake set.

  16. #16
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    Quote Originally Posted by raloftus
    Generally, there are two kinds of problems common to disc brakes. They are vibration and squeal, and while they may be related, I feel they may require different solutions.
    Theyre all vibrations. Just different frequencies. Changing anything in the system, one can change the resonant frequency.

  17. #17
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    it sure gummed up the pistons on my brakes!

  18. #18
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    Check the suspension pivots and rear wheel. Loose or worn bearings will let the brake vibrate and squeel. Check this is espeially if you feel the frame vibrate under you.

  19. #19
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    Sounds like the dreaded turkey gobble. Read this.

    Note, the new Elixer 7/9/XX rotors (available in June) are supposed to cure the turkey gobble. I have my LBS looking into getting me a set of XX's for my problem.

  20. #20
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    just talked to a guy at sram who was pretty helpful. he suggested adjusting the banjo bolt angle and seeing if that helps. but other than that he didn't advise that i try something like sanding pads or cleaning the rotor with brake cleaner. it sound like we also didn't exactly follow proper bedding procedure which involves 20 total stops... half high speed and half lower speed.

  21. #21
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    Quote Originally Posted by McKraut
    just talked to a guy at sram who was pretty helpful. he suggested adjusting the banjo bolt angle and seeing if that helps. but other than that he didn't advise that i try something like sanding pads or cleaning the rotor with brake cleaner. it sound like we also didn't exactly follow proper bedding procedure which involves 20 total stops... half high speed and half lower speed.
    I've followed their bedding procedure to a "T" 3 times with three new sets of rotors & pads. I truly believe it's a smokescreen so they can blame the results of crappy design on the user.


    Here's what the new ones look like.

    http://www.bikeradar.com/news/articl...t-look--29474/

    Avid have ditched the slots of the old G2 rotors in favor of holes in the brake track of the newly sized HS series rotors to eliminate their dreaded ‘turkey gobble’ screeching and sensation felt through the lever during slow to medium power use, as well as further reduce their weight.

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