Page 2 of 2 FirstFirst 1 2
Results 16 to 21 of 21

Thread: 83 K75S - Rear Brake Master Cylinder

  1. #16
    Registered User dieselyoda's Avatar
    Join Date
    Mar 2013
    Winnipeg, MB, Canada

    Ok, my answer, just from my experience and not a fact to be held as the truth in cour

    Quote Originally Posted by 98lee View Post
    So what is the acceptable amount of leakage on YOUR BIKE?

    How does that compare with BMW's recommendation?

    What would be the result of a failure on that particular system?

    A leak is a warning. Will you heed it?

    New brake seals in undamaged bores do not leak, even in cold weather. Worn or damaged seals or bores do.

    No amount of leakage in a brake system is acceptable to me. I never had the luxury to see if that little "wetness' would stop. I was working on valued customers machines. I couldn't gamble.

    BMW don't know SFS.

    The results is the same as unforeseen rupture of a brake line, a skid mark in your underwear at the best.

    A leak is a warning. It depends on how much patience you have and an understanding.

    ALL NEW SEALS LEAK. There is another new topic and thread right there.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case, my baby, fast, fun)
    3xR90/6, two just sold, one for a sidecar. 1983 K100RS (Cafe now)
    Very Rough R80RT. 1987 K1100RS (freaking hooped I think)

  2. #17
    3 Red Bricks
    Join Date
    Jan 2007
    Pleasanton, Ca.
    I am also familiar with powered hydraulic systems. (Military aircraft and industrial) The one thing that all your examples have in common and are not present in a brake system is a running PUMP.

    Minor leakages (drops) will not effect the effectiveness of those systems as any oil leaks out that was supposed to lower the ramp or landing gear is replaced by the pump from the reservoir. The ramp or the landing gear will continue to lower until they reach their limit switches.

    In a brake system, the "pump" is the master cylinder. Instead of running and providing what ever fluid is needed, it is limited by its single stroke displacement. If ANY brake fluid bypasses the seals, the resultant output is reduced. This causes the pads to have less travel/pressure available.

    With a bike brake system, we are talking about less than 1/2 thimble full of fluid displacement. A few drops bypassing the seals is a huge percentage compared to the large systems you referred to. If your master runs out of travel before you stop, you may not like the outcome.


    Ride Safe, Ride Far, Ride Often

    Lee Fulton Forum Moderator
    3 Marakesh Red K75Ss
    Mine, Hers, Spare

  3. #18
    Instigator cele0001's Avatar
    Join Date
    Feb 2014
    Jacksonville FL
    Dudes, slow down a little.
    This aint jo mamma.
    If the leak is acceptable to you there is nothing that anybody can say to make you think differently, but they might disagree, that is just the nature of the conversation.
    My 2 cents, rear brake small leak Ok with me, front brake must be 100%
    I want to be unique, just like everybody else.

  4. #19
    Last edited by ghyber; 04-06-2014 at 02:51 PM.
    1993 K75S Mystic Red Pearl
    2007 K1200GT 997 Blue

  5. #20
    Instigator cele0001's Avatar
    Join Date
    Feb 2014
    Jacksonville FL
    Quote Originally Posted by ghyber View Post
    "[I]Lee, re-read my post above again, this time slowly.
    Now granted I am the new guy here and I don't know the history but this post definitely has attitude behind it.
    The easiest way to ignore somebody is to just ignore them, it requires no energy.
    I want to be unique, just like everybody else.

  6. #21
    Dum vivimus vivamus ted's Avatar
    Join Date
    Mar 2003
    Wow! Lee has forgotten more about K75s than most will ever know, and generously (and patiently) shares his knowledge with any and all who ask. I'd suggest withholding opinion of him for some other forum, and instead if there is a disagreement challenge the content of his posts.

    One can either take his voluminous knowledge or leave it, I would say however that in my many years of happily absorbing all of the many, many contributions he has made here, one ignores his advice at one's own peril. As a side note, some years ago I was stranded in the middle of West Virginia with a most vexing problem, I didn't know Lee and had never met him but he still offered and did call me and spent a good amount of time walking me through troubleshooting and fixing the problem.
    "A good stick is a good reason"
    1994 K75RT
    Moto Pages

Posting Permissions

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