Shimano Mineral Oil Black

iwilldoit
iwilldoit Posts: 710
edited April 2017 in MTB general
Hi All

Up at Revs yesterday with my 12 year old, he rode Far Side all day and around diner time his rear brake started to play up, everytime the bike came off the uplift trailer he had no rear brake, pump it a few times and it was back, as we had had most of the day we didn't bother having a look at it.

Today I thought I would give it a good bleed, no air came out but the fluid was black, it was also changed around 6 weeks a go and it was slightly discoloured, the bike is a 2012 Nukeproof Mega Pro Am ruing Shimano SLX brakes.

Is it a case of working the brakes to hard/hot or could it be something else, the suspension was getting quite warm after a run as well, he only uses the bike for DH riding.
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Comments

  • ade555
    ade555 Posts: 216
    edited April 2017
    Discoloration of brake fluid and that goes for mineral or Dot most likely is down to contamination, I don't think you can over heat mtb brake fluid, you saying that you had to pump the brake few times then it come back would point to leak in system, that could be down to seals ect., flash the system with fresh oil, I would say hold that brake lever tight for few min and see if goes soft.
  • The Rookie
    The Rookie Posts: 27,812
    Aluminium debris, flush and it will be fine. Very common for it to go dark and cloudy over time.

    Not due to air and it's pretty impossible in a 'sealed' system anyway.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • ade555
    ade555 Posts: 216
    The Rookie wrote:
    Aluminium debris, flush and it will be fine. Very common for it to go dark and cloudy over time.

    Not due to air and it's pretty impossible in a 'sealed' system anyway.


    So how would you explain this if there is no air in system?
    everytime the bike came off the uplift trailer he had no rear brake, pump it a few times and it was back
  • The Rookie
    The Rookie Posts: 27,812
    By reading what my post actually said......
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • ade555
    ade555 Posts: 216
    The Rookie wrote:
    By reading what my post actually said......


    I did read your post, and no need to get grumpy over it :D , I can understand why the oil change color due to aluminium debris but would this create a problem where he had no brake every time taking the bike of lift?
  • The Rookie
    The Rookie Posts: 27,812
    No, the colour hasn't given the symptom of the long lever, that's either underfilled or air in the system or both, if the pads are at the end of their life it would exacerbate it.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.

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