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Wretched brake noise (video)

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by jack_1313, Aug 12, 2012.

  1. I’m having some trouble with a noisy back brake on my Hornet 250 after installing new components. There's a bit of a story to it.

    The back disc had been slightly warped for as long as I’ve had the bike, providing uneven braking force at low speeds. I’d attempted to replace the pads a few months ago, but the new pads (Metal Gear) quickly developed a horrendous deep vibrating-groaning sound when light pressure was applied to the brake pedal, which was not alleviated by cleaning the brake parts. So I put it down to the bad disc and reinstalled the old pads, which had some meat left on them and made no noise.

    Recently I needed to replace the front disc and figured I’d get a new disc for the back as well. Installed the new back disc and pads (both Metal Gear) and, sure enough, it quickly developed the same wrenching sound as I began using and bedding in the parts. I had a spare set of brand new cheap pads lying around, so I swapped them in and the sound again quickly manifested. So that’s several different sets of new brake pads on two different discs that produce the same problem.

    In the video below, you can hear the noise as I slowly turn the back wheel by hand while applying light pressure to pedal. The noise does not occur if more force is applied or at higher speeds, but does tend to occur, to a lesser degree, when rolling along slowly while the brake is not in use at all.

    Thoroughly cleaning the brake calliper and piston had no effect.

    I’ve got some ideas about what the problem could be, the first is being bad rear wheel alignment. The sound does not occur if I loosen the axle nut, so that could be a clue.

    The second is that the parts manual for the bike indicates that the rear pads should have shims, which I don’t have:
    I’d be surprised if that sound was the result of a lack of shims though.

    Anyhow, any ideas would be very helpful!
  2. Well I doubt I can help but that horrid sound woke my dog up and made her decide to bite my arm as she thought I was making the sound...****ing dog
  3. You said loosening the axle nut stops the noise. Have you tried removing the brake caliper and seeing if the noise is still there?
    Maybe it's in a bearing or spacer and not the brakes.
    Clutching at straws i know but you have covered most things with the brakes so need to consider something else.
    Good luck.
  4. Nice

    This can be sorted ill write a list use some or all
    Noise comes from two possilbities 1 you have eliminated.
    1 foreign object in pad kr tkuching disc - stone / worn pad / shim etc...

    2 vibration.

    To eliminate sound from vibration some things that can be done
    1 have clean pads and disc
    2 bevel leading edge of pads ( does sound happen in reverse ? )
    3anti squeal compound or substitute with silcone between pad back and caliper
    4 slides should mkve freeling and be lubticated
    5 thats a good start fir now
    • Like Like x 1
  5. Thanks for the insight guys!

    Thanks for the heads-up - I'll try not to brake near any dogs.

    Yep, the noise is definitely connected at least partially to the brake disc/pads/calliper. The wheel makes no noise when the calliper is not installed.

    1. Definitely clean - used brake cleaner on the new disc before installing it.
    2. Good idea. I'll try this if other solutions don't work.
    3. Well, the new shims are coming in tomorrow and will fit between the back of the pads and the calliper. Hopefully this will eliminate the vibration.
    4. Parts were well lubricated before installation.

    Thanks guys, I'll keep at it!
    • Like Like x 1
  6. Quick update:

    Honda has the right hand side shim, but can't get the left shim in for two to three weeks -argh!

    I suspect the noise is being caused by contact between the back of the left (stationary) pad and the caliper. When I placed a thin piece of cardboard between them the noise stopped, although the wheel didn't spin as freely.

    I applied anti squeal on the back of the pad plates. Applying "a thin layer" as per the instructions had no effect, but a more liberal application has reduced the noise without eliminating it.

    Haven't been able to check rear wheel alignment yet thanks to Bunnings marking their threaded rod with incorrect sizes - so I've got nothing to take precise measurements with. Don't have a level enough surface to use the string method.
  7. Point 2
  8. A quick update:

    I was going to wait until I could get both shims in before further addressing this problem, but the noise was driving me nuts so I picked up the left shim and installed it. That eliminated the noise... for half an hour. So the problem remains.

    One thing that became immediately obvious once I had the shim is that the backing plate of the after market pads I am trying to use is smaller than the backing plate on the OEM pads. I discovered this by noticing that the shims clip on 100% snugly to the OEM plates (even have to force them a little), whereas they just fit loosely over the after market plates and don't clip on at all. I think this could account for the vibration.

    Today I will try beveling the pads as per Phil's suggestion. If that doesn't work I'll order some OEM pads.
  9. your brake calliper is seized. needs a rebuild.
  10. Hi Pete, thanks for taking a look - I really appreciate it as I understand that it's not in your interest to help with backyard mechanics.

    There reason I didn't think the piston was seized was that I can't find any other evidence suggesting that. The brake doesn't seem to be dragging. As a test, I did my 10km commute to work without touching the back brake, then put my hand on the disc. It was warm but not hot enough to be uncomfortable to hold. The wheel also spins quite freely when the bike is on a stand. I removed the Honda shim because this did seem to be creating friction when used with the aftermarket pad - not on account of the piston, but rather the caliper had to slide a bit far forward to fit the stationary pad and shim between it and the disc, so as that the rubber bushing that fits over the caliper sliding pin was a bit too compressed and wanting to force the caliper backwards. The piston is also in good visual condition, and the sound goes away temporarily after I clean the disc.

    I'm expecting some genuine pads to arrive early next week (NOS). I'd like to wait for those so that I can completely eliminate cheap pads as a potential source of this problem.

    Provided that doesn't resolve the problem, I'll shoot you a PM about getting this caliper rebuilt.