Howling rear hydraulic disc brakes - nothing I do stops it!

badgerjockey
badgerjockey Posts: 36
edited September 2011 in Workshop
Hey up all,

My rear Shimano M486 brakes (non-series but has been good in the past) just don't stop howling when even a modest amount of braking pressure is applied and it's driving me mental, let alone making me look like I'm hanging off the brakes on every corner (hehe, it matters!).

So far I have:

-bled them
-trued the rotor
-reset the brake caliper on the post mounts for perfect alignment
-changed the pads for new ones
-degreased and cleaned and dried the rotor
-detached and reattached the rotor off the hub...

So, what's left? Almost certain they're not contaminated pads. How about gunk in the piston seals etc? How do you clean or renew them and can you even buy new parts?

Any thoughts on the issue would be great.

H

Comments

  • mattv
    mattv Posts: 992
    Possibly still a contaminated rotor. IPA doesnt always get it all off. Else sometimes they just howl, especially in the rain.
  • al2098
    al2098 Posts: 174
    Strange it still does it after all that.
    If it is oil contaminating them you will just have no breaking power.
    Overspray with wd40 has been known to cause temporary squeaking but this is obviously chronic..
    Its almost always caused by water moisture, soap residue or possibly that old chestnut, misalignment.
    are they perfectly alligned.?
    How do you bed them in? Bedding them in on a DH run could glaze them and cause horrible squealing (but usually when wet).
    Try to re-bed them. Get some fine sandpaper and rough the pads up and bed them in gently. If they are somehow contaminated, the sandpaper will be a waste of time though.. I wouldn't bother toasting or baking them cause if they are contaminated they are toast anyway.
    Good luck

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