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Front Brake Caliper Disc Drag - help

Discussion in 'XJ Technical Chat' started by maybe4, Jul 11, 2018.

  1. maybe4

    maybe4 Member

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    A few years ago I rebuilt the front brake caliper and installed stainless steel brake line from Chacal (awesome kit). Stopping power is excellent - my front brake lever is almost too firm with very little travel (I'm not complaining I like the stopping power). however, I noticed that my front wheel will not free spin. I can of course, turn it by hand, but there is drag which seems a little excessive from the caliper pads on disc. The drag prevents any free spinning of the wheel. I do NOT notice any drag while riding but I'm sure I need more clearance between the pads and the disc. With the bike straight up & level I have a small visible air bubble in the master cylinder (seems right to me). Couple of questions

    1) should there be more travel in the brake lever? I am fully engaged at almost immediately (I'd say 20% travel) but I just thought that was because the stainless steel lines are so awesome (and yes I do have the proper clearance gap between the adjuster and the master cylinder piston).

    2) suggestions very much appreciated on what my problem might be and how I can increase the clearance between the pads and the disc. Obviously I'd like to start with the simplest solutions before taking everything apart and rebuilding the caliper (again). Would bleeding a little fluid out help ?
    Thanks All!
    1982 XJ650(J) Maxim - love this bike!
     
  2. Stumplifter

    Stumplifter Well-Known Member

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    Did you also clean/rebuild the master cylinder?
     
  3. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Did you polish the caliper pin?
    That caliper has to be able to rotate freely or the pads will tend to drag.

    How long ago was the brake fluid replaced?
    This should be done every two years.
     
  4. maybe4

    maybe4 Member

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    I did both of those (rebuilt master cylinder and also new fluid) but that was 5 years ago. Very low miles since the rebuild but still it was a long time ago.

    I'm thinking I just have too much fluid in the system thereby keeping to much pressure in the line. Just as an experiment, what would be the best procedure to bleed a few oz of brake fluid out ? (thank you both for your replies)
     
  5. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Miles don't matter. Brake fluid absorbs moisture regardless of whether you ride the bike or not.
    Bleed through until new clear fluid comes out, and hope that there are no big goobers of jelled brake fluid in the system (or at least that any goobers flush out).

    That might not be the issue, but it's required maintenance, and easy to do. It also eliminates that possible problem from the list of things to check.
     
  6. Chitwood

    Chitwood Active Member

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    Could it be possible that a chunk of something left over in the brake system is covering the return port in the MC? Would that cause the OP's symptoms?
     
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  7. Colin 85 700

    Colin 85 700 Active Member

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    One tip, if you can without ripping it, extend the plunger in the caliper (no pads) then pull the boot off the piston from the inside, spray fogging oil on the piston to remove rust n lubricate, reinstall the boot and compress the piston again, bleeder open, reinstall with pads on bike, activate brakes, then open with a screwdriver, prying the caliper open a bit, activate brakes, do this few times and try, should alleviate a sticky caliper. Also as mentioned above check pins on pads and the shiny steel pad slides, use tiny bit of brake grease on all surfaces. (zNOT the disc, lol! )
    Hope this helps.
     
  8. Colin 85 700

    Colin 85 700 Active Member

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    Note for above: Don't over extend the caliper! If the plunger falls out you are F'ed only let it como out about 1/4 inch 9mm
     
  9. Colin 85 700

    Colin 85 700 Active Member

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    Maybe 3/8 inch 10mm
     
  10. maybe4

    maybe4 Member

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    thanks guys.....appreciate the feedback. I like the fogging oil idea.

    question....if I just want to bring down my fluid level a bit to see if it makes a difference, and correct me if I'm wrong, but I should just be able to take of the top to the master cylinder and syringe a little fluid out - right ?? I don't actually have to bleed out the fluid through the bleed screw right ? I just want to start with that just to see if overfill of the master cylinder is my problem (even though it's probably not :)
     
  11. k-moe

    k-moe Pie, Bacon, Burbon. Moderator Premium Member

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    Correct. You can just draw fluid out of the top of the master. Make sure that whatever tool you use is very clean.
    Is the sight glass so foggy that you can't see the fluid level?
     
  12. maybe4

    maybe4 Member

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    sight glass is clean and I drained a little fluid out - no difference. I know firm is good (as opposed to a squishy front brake) but mine is rock hard. great stopping power but almost no lever travel - just seems to firm to me but maybe that is all well and good. the MC outlet port is clear, everything looks good in the master cylinder. I have a feeling it's something in my caliper - going to have to remove it and see what's going on. Might as well bleed the whole system now and replace the fluid with the mityVac (been a while since I used it). The mityVac is a better way to go than old school lever pumping isn't it ?
     

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