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Thread: Marta SL growl

  1. #1
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    Marta SL growl

    2011 Marta SL, rear on a 160 (Storm) rotor mounted to Black Cat swinging dropouts on a custom steel frame. The rear brake has a vibration type growl/squeal during light to moderate braking, only when cold. After using it a bit on a long downhill it quiets down. I've tried everything I can think of- cleaned rotors with alcohol, sanded rotor, changed rotor, cleaned pads, sanded pads, tried new Magura Performance pads (3 times), cleaned pistons with alcohol, worked pistons in and out as I was cleaning. Everything is tight, rotor bolts, mounting bolts, etc. I've done most of these fixes multiple times. I can make it quiet for a while but it always come back. The only thing I haven't done is to bleed the brake but it exhibits no signs of it needing to be bled.

    The brakes were dead quite for the first 8 months, or so, of use and then the rear started making the noise. I love 'em otherwise.

    Suggestions? Thanks!

  2. #2
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    is the rotor true? even on new ones i have had to adjust
    when cleaning pistons did you use some mineral oil (magura blood) on the piston to coat the seals?
    i have used other brand pads- jagwire, koolstop and discobrakes with some success
    also i have had better luck with this stuff instead of alcohol for some reason

  3. #3
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    Thanks, Natrat. The rotor(s) is true. I've tried 2 Magura and one Avid. I've also tried realigning the caliper multiple times. I haven't tried lubing the pistons with mineral oil, I've only cleaned them. I'll try it, it's odd that that might contribute to the vibration issue though.

    I just recently tried a set of Galfer pads, same issue after they bedded in. I've ordered a set of 'Endurance' pads just to see if it makes a difference.

    Thanks for the advice!

  4. #4
    rod skinner
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    Make sure all your hardware is tight. Metal expands when it warms up, might be why the vibration stops.

  5. #5
    Magura N. America Svc Mgr
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    Hello Rocky Rode

    You know the problem is a vibration as you mention and it wasn't around until recently after you say 8 months. Is that 8 months and many miles or has it not been ridden much?
    I ask because if it hasn't been ridden much, then I would also assume as you do that it is an alignment issue and the pads are just starting to get aligned enough to make enough friction (some percentage towards 100% pad interface)
    If thats the case, either you can try to persevere and ride/brake through the noise (if the misalignment isn't severe) until the pads are 100% or put a brake tab machining tool on your frame to align the tabs to the proper alignment of the hub plane. I would do this unless...

    If the bike has constant 8 months of mileage on it, I would look at that , "Black Cat swinging dropouts on a custom steel frame" interface for wear or possibly a little tolerance that could have developed from hardware?

    Let me know what you think.
    Jude

  6. #6
    On your left.
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    How do you really accurately align and center the caliper to the rotor? Something better than the loosen screws, squeeze lever technique.
    M

  7. #7
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    Quote Originally Posted by judemonica View Post
    Hello Rocky Rode

    You know the problem is a vibration as you mention and it wasn't around until recently after you say 8 months. Is that 8 months and many miles or has it not been ridden much?
    I ask because if it hasn't been ridden much, then I would also assume as you do that it is an alignment issue and the pads are just starting to get aligned enough to make enough friction (some percentage towards 100% pad interface)
    If thats the case, either you can try to persevere and ride/brake through the noise (if the misalignment isn't severe) until the pads are 100% or put a brake tab machining tool on your frame to align the tabs to the proper alignment of the hub plane. I would do this unless...

    If the bike has constant 8 months of mileage on it, I would look at that , "Black Cat swinging dropouts on a custom steel frame" interface for wear or possibly a little tolerance that could have developed from hardware?

    Let me know what you think.
    Hi Jude,

    The bike is ridden a lot. I'm on my 3rd set of pads since mid 2011 and this is in a dry environment. I think the next step is to have the brake tab interface surfaced. It's odd that it would have changed but it will be good to know for sure. The pads seem to wear evenly and the rotor doesn't drag at all. Performance is great.

    When I sand the glaze off the pads and clean all surfaces- pistons, back of pads and rotors with alcohol the noise goes away completely for 3-6 hours of riding and then it always comes back. I do bed the pads in after doing this.

    I really appreciate your input! It's impressive that someone from Magura will actually take the time to respond to questions like this.

  8. #8
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    How is your rear wheel? Are the bearings still good and is the spoke tension even? I had a rear wheel resonate like crazy until I put new bearings in and trued it. I also use blue thread lock on all the relevant threads.

  9. #9
    On your left.
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    The threads of the thru-axle on my frame are part of the derailleur hanger, which is held on with 2 small countersunk screws - these can and have loosened leading to immediate rear wheel wobble - therefore rotor wobble and braking issues.
    M

  10. #10
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    Quote Originally Posted by rocky rode View Post
    noise goes away completely for 3-6 hours of riding .

    although it's probably not quite right i have to sterilize the rotors each ride to guarantee smooth performace

  11. #11
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    Thanks for all the great input everyone! I've used two different wheels, one of them is new. Bearings are fresh, smooth and tight. Skewer is as tight as I'm comfortable with. All bolt connections in the rear triangle have been torqued, more than once.

    When I get the brake mount surface faced I'll report back. I'm in a tiny town and will have to make a trip to somewhere that has a tool, so it may be a while.

  12. #12
    Tool
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    Something I've done to silence my brakes on the trail is to throw some dirt on the rotors. As dirt is an abrasive, it can often correct whatever is going wrong at the pad/rotor interface that is causing the vibration and noise. This is obviously just a workaround and not a solution, but it may help you enjoy more quiet rides while you figure out a long term solution.

    -Pete
    I can barely get my mouth around it.

  13. #13
    Magura N. America Svc Mgr
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    That is accurate, loosen the hardware, squeeze the lever blade to pressurize the system but before tightening the hardware,
    Make sure the caliper is positioned evenly over the rotor by forcing it the direction you need.
    The pistons can be somewhat "cocked" in their seals and still work fine but the alignment may be off or too much to one side of the caliper.

    You can position it before tightening down the caliper hardware.
    Jude

  14. #14
    Magura N. America Svc Mgr
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    Rocky Rode

    Can you show a photo of the Black Cat swinging drop out ? I suspect this may have moved a little causing the tabs to also move under load or braking. Could this be a possibility?
    Jude

  15. #15
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    Quote Originally Posted by judemonica View Post
    Rocky Rode

    Can you show a photo of the Black Cat swinging drop out ? I suspect this may have moved a little causing the tabs to also move under load or braking. Could this be a possibility?
    Hi Jude, thanks again! As you can see the Black Cat drop outs are pretty beefy. I doubt the issue is with the drop outs themselves. There are 5 frames around here that use them and none of them have squeal issues. Only one has Martas but it's quiet too.
    Attached Thumbnails Attached Thumbnails Marta SL growl-brakes-002.jpg  


  16. #16
    Magura N. America Svc Mgr
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    Thanks for the photo.

    Yes I agree it does look substantial but there is a lot of components there, all potential areas of concern from torq and time.
    Also, that doesn't look like a Magura caliper adapter and may not be part of the problem and are those Galfer brake pads?
    Jude

  17. #17
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    Quote Originally Posted by judemonica View Post
    Thanks for the photo.

    Yes I agree it does look substantial but there is a lot of components there, all potential areas of concern from torq and time.
    Also, that doesn't look like a Magura caliper adapter and may not be part of the problem and are those Galfer brake pads?
    You're right, I believe the adapter is an Avid. Does it matter? It's been there from day one. As mentioned earlier I just recently put the Galfer pads in just to see if it made any difference and it didn't. I just haven't pulled 'em off yet. Does this mean my warranty is history?

  18. #18
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    Turn your skewer around...the lever on the drive side.

  19. #19
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    We're not worried about that.
    Just trying to add up the possible contributors. No worries.
    Jude

  20. #20
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    Then turn it around. (Or get rid of the skewer. You have six metal bolts there, yet you are holding your wheel on with an external cam skewer with a plastic concave washer.)
    Last edited by knl2stl; 11-09-2012 at 07:11 PM.

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