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Rear brake disc "honks" at me

Discussion in 'Technical and Troubleshooting Torque' started by Smokae, Aug 22, 2010.

  1. You may recall I was concerned about an odd noise from my bike in another thread. I've finally identified with 100% certainty the source.

    So there is a 1inch patch on my rear disc, that at low speeds, when spinning through the calipers, makes a "honk" sound and sents a substantial vibration through the caliper. The previous owner claims the rear disc was new.

    I took sandpaper to the disc thinking it might be shit pads leaving a residue, it certainly reduced the noise but it is not gone and is very noticeable at low speeds.

    Mind you sometimes the sound won't start happening until after I end up using the rear brake at some point and then it will happen for the rest of the day.

    Once I get up to around 20kph the noise disappears. But pulling up to the lights it can be so loud that I notice passengers in cars turn their head at the "weird honking shit noise from behind us".

    Should I be worried?

    Should I take the calipers off and change the pads? Will I need to bleed the brakes to make the pistons go back in, I only ask as I was forced to do this the one time I changed the pads myself on my GS500 and found a piston was jammed open due to a dodgy seal and I imagine the seals maintain a extruded-distance that is constant as the pads wear down in order to maximise the efficiency of braking, i.e. distance from pad to disc and the time involved in travel.

    Thanks guys and girls ;)
  2. My Pantah does the same when you push it around backward.
  3. sounds like pad shudder to me
  4. Is pad shudder a safety issue?

    It only does this when rolling forward unlike your pantah haha :p
  5. i've never heard of it turning bad, then again everyone i've heard of having the problem had it fixed one way or another
  6. You are riding too slow. Pull over and let it past.
  7. At least some brake pads are designed to start getting noisy when they're due for replacement. How much meat is left on them?

    If the brake isn't actually juddering or pulsing, indicating a warped disc, and the pads are OK, I wouldn't worry about it. It's likely to go away in due course.

    It would be worth having the caliper apart to make sure nothing's seizing, then putting it back together with a smear (no more than that) of Copaslip on the pins and the backs of the pads. Don't get any on the friction faces or you'll die.
  8. Fixed that for you Pat.
  9. similar to Pat, you might need to put a kit through the caliper. The pistons could be sticking "down" until the disc knocks them back out again.
  10. Thanks for the kind words guys, I had a chuckle at the emphasis of "on the back of the discs".

    Heaps of meat on the pads still, almost brand new.

    I remember with my old Gs500 i managed to seize a piston and pop a ring that made the piston stick out. I had to bleed the brakes in order to fix it.

    Am I going to have to do this to push the pistons back in if I extend them by pressing the brake lever while the calipers are off the disc? I assume they have to be extended out in order for me to clean them without splitting the caliper.
  11. hahahaha, thanks man, that's the funniest thing I've read for a while
  12. I had the same problem after putting a new disc and pads on the rear of my bike, a bit embarrassing coming up to the lights! I solved it by just sticking the old pads back in. My take on the problem was that with more meat on the pads the caliper was not releasing them properly as it was probably a little sticky. A disc is unlikely to be 100% true and it will drag more at some point. You may not have some old pads to stick in but eventually they will wear down- otherwise you may need to overhaul the caliper to free it up.
  13. Yeah well these pads are practically new, I was actually surprised how much meat is on them for brake pads, much more than what my ZZR250 had.