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surging or 'hunting' juicys - any ideas?

shefbikershefbiker Posts: 255
edited December 2010 in MTB workshop & tech
hi
i have juicy5s, and the front one has a substantial 'surge' in brake power once a wheel revoloution. there doesn't seem to be any feedback at the lever, just a major decelleration of the bike.
it's so significant that it basically makes the bike impossible to control anywhere near the limit because the front brake is so unpredictable.
any ideas what's causing it? or what i can do about it?
thanks

Posts

  • nicklousenicklouse Posts: 81,520 Lives Here
    how old are they?

    still got "the grind" patten on the rotors?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • i recently (in terms of miles, at least) upsized the rotor from 160 to 180, so relatively new i guess. not sure about the pattern, but i suspect it remains given the lack of use.
    why?
  • i guess the inference is that the pattern is in someway creating a differential of grip on the disk surface?
    how would i remove the pattern? sandpaper? wire wool?
    would you expect to routinely do this to a new disk? i've not heard of it before..
    Thanks
  • diydiy Posts: 6,680
    Check you got the rotor on straight
    check that you didn't get any muck behind the plate that would hold it proud
    check the tri align is properly adjusted after bedding the pads in
    Check also that there is nothing wrong with your bearings in your hub.

    Does the wheel spin freely?
  • gongagonga Posts: 225
    The same thing happened to my juicy 5 front.
    I sent mine back(with the bike) and got it swapped out for an elixir 5.
    Not sure what the problem was but a sticky piston was mentioned by a few that looked at it.
  • MoooseMooose Posts: 47
    I had the same with new elixir r (front brake). Swapped the rotor with an old Hope one of the same size, and problem disappeared. I believe it is to do with the surface on the disc, and I'm going to wear in the problematic rotor on the back of my DH bike, where the pulsing/surge doesnt cause the dangerous effect that it does when on the front.

    Do you have a spare rotor of the same size to test? Or if you have same size front and back you could try swapping?
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