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squealing rear brake

squealingdawgsquealingdawg Posts: 7
edited September 2010 in MTB workshop & tech
The Bike is about 5 months old. The squealing started mid way down a bike trail at Whistler for no apparent reason other than maybe over heating ( dry and 21c). Here is a list of repairs so far.

1. Cleaned and sanded rotor, sanded pad, realigned caliper.
2. Bled and replaced all fluid in brake line and caliper.
3. Replaced pads.
4. Replaced caliper.
5. Replaced pads again.
6. Cleaned and lubed pistons. Cleaned caliper and rotor with alcohol.
7. Smeared copper grease on pistons between pad and piston.
8. Swapped front to back brake caliper assembly.
9. Replaced pads again.
10. Tightened frame bolts.
11. Cleaned and sanded surface between adapters and frame mount.
12. replaced caliper and pads again. re-torqued mounting screws (shop did this)

It seems that the noise and vibration is being transmitted through the frame somehow and not caused by the brakes themselves. The bike is hard to control with the rear brake at higher speeds when this occurs.

My riding buddy insists that I need to try a larger diameter brake caliper( he is sick of the noise also). I plan to re-torque all the frame screws and replace the rear wheel



What else can I do? Craigslist?

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    read the topic on squeaky brakes in the FAQs?

    also what is the brake?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • konadawgkonadawg Posts: 447
    Hi assume you mean Kona Dawg.

    Yes common enough, mine did this and a mate's is also doing this at the moment.

    It seems to be resonance/vibration of the brakes transmitted and amplified through the frame.

    I remember that replacing the seatstay bushings had some effect but the total fix came from using brake pads from a different manufacturer. Don't know whether you tried that or simply replaced like with like. I ended up with several pairs of pads tagged as "front use only" :roll:

    So try that first.

    Also check that your hub is not loose, this last guy I mentioned just wrecked his rear brake at Morzine, replaced with a different system and he still has the problem - may well be that the pad materials were near enough identical despite, but one thing for sure his hub bearings have a lot of play in them and that certainly may be a major contributor.
    Giant Reign X1
  • squealingdawgsquealingdawg Posts: 7
    Yes it is a 2009 Kona Dawg. I have used pads from three different manufacturers and switched between metallic and resin base pads. Have not changed the seat stay bushing but the shop did tighten the wheel hub bearing. Swapped bikes with my buddy who has the same Dawg and brake set in a 17" frame. He weights 220 and I am 155, made no difference in the noise although I really enjoyed riding his bike for trial

    I have read the FAQ in this and many other forms. Mostly just fond tips on cleaning or changing brake pad and calipers.
  • nicklousenicklouse Posts: 50,675 Lives Here
    so what are the brakes?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • squealingdawgsquealingdawg Posts: 7
    Shimano 575 Hydraulic Disc. Reread the FAQs and didn't find anything new however I am going recheck the hub for grease leaking out just in case.
  • *AJ**AJ* Posts: 1,080
    Youve not mentioned replacing the rotor?......
  • squealingdawgsquealingdawg Posts: 7
    I listed caliper but should have said Rotor. Its been replaced twice with new pads each time. The caliper was swapped from front to back once.
  • nicklousenicklouse Posts: 50,675 Lives Here
    Ok what rotor? and fitting.
    what pads? shimano ones? organic or sintered?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • squealingdawgsquealingdawg Posts: 7
    Found a fix at another bike shop. New brake bigger rotor, no squeal.
  • konadawgkonadawg Posts: 447
    Cool, you changed the frequency of the vibration and the frame no longer resonates.

    Out of interest to everyone who may have this problem, it can manifest itself irrespective of brake types (mine were hope, friend's were shimano changed to formula) and it's really "one of those things" that only a seatstay redesign would probably fix for good, but for the rest of us it's suck it and see.
    Giant Reign X1
  • squealingdawgsquealingdawg Posts: 7
    I spoke to soon. The brakes worked fine for a couple of runs down short hills in Bellingham however after one ride down lower "Crank it" at Whistler they started to squeal again. By the end of the day it was almost unbearable. I adjusted and tightened every bolt and screw I could on the brakes and frame but it made no difference to the squeal/vibration. The new rear brake I had install is Avid Elizer with an 8" rotor. Was Shimano DLX 525 Disc 6" before. This can't be a brake problem, it has to be something with the frame, wheel hub or maybe even wheel spoke tuning (just guessing now).

    What can be done to the Seat stay bushing? The bike is only 5 months old and because it spend so much time in the shop has not been ridden all that much but I will re bush everything if necessary.
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