Results 1 to 8 of 8
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    679

    Help bleeding this shimano XT brakes...

    Hi, as some you may remember I wrote the last message about a sticky piston on my XT brakes 08, well after playing with the pistons one almost did pop out (just one side) it didnt pop out completly but enough to release some brake fluid...Well, after that as you can imagine the brake lever was just useless...

    I went to the LBS and bought a bottle of that shimano mineral oil and started to bleed them following the shimano website instructions...it was fairly easy...Now the lever feels just firm at the contact point with the rotor and everything seems fine...I just tapped a couple of times the lines and the caliper to see if any more air bubbles will come out...opened and closed the bleeding nut like 5 times to check that theres no more air inside the system (all this having an eye on the reservouir tank to keep it filled)...

    Anyways, one question I have is, could this mineral oil that splitted over my carbon fiber handlebars damage it?...I tried to clean everything with isopropyl alcohol to kill the mineral oil but there will be always some residue there...could this oil damage CF surfaces?...

    BTW, the piston is STILL getting stick...one piston protudes more than the other...but I think that its because one of the brake pads has more wear than the other ---- Also when centering the caliper (PM) the caliper just bites the disk perfectly centered...so I think that the uneven piston movement is because of the uneven pad wear...could this be true?


    Anyways, I want to thank all the people who helped me here with very useful comments! THANK YOU ALL!

  2. #2
    Meh.
    Reputation: XSL_WiLL's Avatar
    Join Date
    Nov 2004
    Posts
    17,516
    Mineral oil will not damage your carbon bars like DOT fluid would.

    There is almost always a dominant piston. One moves further than the other. As long as the caliper is centered without rub or drag... no problem.

  3. #3
    mtbr member
    Reputation:
    Join Date
    Jan 2004
    Posts
    679
    Thanks for the quick reply will. One more question, with the yellow block inside the caliper how must feel the lever? tottally stiff or just stiff enough as when there`s the rotor?...

    Mine feels just as stiff as when the rotor is in between the pads...maybe a TINY bit harder but not that much...

    I think now the lever is a little more stiff than when it was tottally new...Anyways this brakes have something like 500km of use...so what do you think?

    One more thing...I always transport this bike laying on a side...max time that it seats that way is 1.5 hours...could this affect the brake feel?

    What do you think about the Clarks Mineral oil?

    thanks!
    Last edited by fran; 01-07-2008 at 08:19 PM.

  4. #4
    wyrd bi ful rd
    Reputation: chinaman's Avatar
    Join Date
    Jun 2007
    Posts
    1,724
    The stiffness in the lever is ok ... as long as you have filled up the reservoir and there is no air pockets underneath the diaphram (quite difficult to achieve and to confirm) putting the bike on its side will be ok ... even if there is some air there it will quite 'difficult' but possible for the air to get into the tiny holes at the bottom of the reservoir ...

    I have turned my bike upside down a few times and have even left it overnight and then when it is turned uppright again ... the levers are ok.

    It is the forks that you should take note not to pump it straight away after it has been upside down but to let it settle for awhile before pumping it as oil would have collected on the other side of the forks ...

  5. #5
    Meh.
    Reputation: XSL_WiLL's Avatar
    Join Date
    Nov 2004
    Posts
    17,516
    Laying the bike on its side shouldn't be a problem. If you got all the air out... even upside down should be fine.

    To get any last bits of air up into the resi, rubber band the levers down overnight.

    Just stick with the Shimano mineral oil. If you did a good bleed you won't have to do it again until you spring a leak or replace something.

  6. #6
    wyrd bi ful rd
    Reputation: chinaman's Avatar
    Join Date
    Jun 2007
    Posts
    1,724
    Just as we are on the topic of 2008 XT brakes, has anyone experience that the first pull of the lever, the throw is further than the 2nd and 3rd pull. ie the lever comes closer to the grips than the 2nd and 3rd pull ... the brakes still work ... it is just that they are not as firm on the first pull.

    Been meaning to open up the reservoir to see if maybe I do not have enough fluid in there ...

  7. #7
    mtbr member
    Reputation: Znarf's Avatar
    Join Date
    Nov 2005
    Posts
    1,009
    What also works pretty nice is the following:
    You can turn the whole bike upside down, put a syringe with mineral oil and a hose to the bleeding valve and open it.
    Now move the lever a couple of times carefully and push and pull on the syringe.
    All the air which sits under the membrane will escape to the highest point i.e. the syringe.
    Works beautiful with my Magura brakes.

    Greetings Znarf

  8. #8
    mtbr member
    Reputation:
    Join Date
    Nov 2007
    Posts
    65
    Quote Originally Posted by chinaman
    Just as we are on the topic of 2008 XT brakes, has anyone experience that the first pull of the lever, the throw is further than the 2nd and 3rd pull. ie the lever comes closer to the grips than the 2nd and 3rd pull ... the brakes still work ... it is just that they are not as firm on the first pull.

    Been meaning to open up the reservoir to see if maybe I do not have enough fluid in there ...
    Yes i have noticed this, although i only find it when i first pump the brakes before the ride, i pump the brakes to see if they work properly before i go anywhere anyway so it dosent matter. It may happen elsewhere but i dont notice it as im too busy riding.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •