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Thread: synthetic brake fluid

  1. #1
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    synthetic brake fluid

    I was going to add a little brake fluid to my 2003 r1150rt, the two stores that I went to, to get the brake fluid, only had synthetic. I was wondering if it is O.K. to mix them? The guy at the parts store said that it was, but I wanted to make sure. I'm talking about DOT 4 brake fluid.
    Thanks

  2. #2
    Happily Bent dieselyoda's Avatar
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    Nooooooooooooooooo

    Quote Originally Posted by samo View Post
    I was going to add a little brake fluid to my 2003 r1150rt, the two stores that I went to, to get the brake fluid, only had synthetic. I was wondering if it is O.K. to mix them? The guy at the parts store said that it was, but I wanted to make sure. I'm talking about DOT 4 brake fluid.
    Thanks
    I'm sure someone will challenge my statement, seems like that is the way it is.

    I can't recall exactly the difference, been a while and I have CRAFT disease but, DOT 2-4 were polyester ethylene glycols with varying degrees of each compound. That's why if you spilled some they ate your paint and if the family dog got some, DEAD he'd be after a painful and agonizing passing.

    Synthetics are polyvinyl propylene glycols with superior properties and great resistance to hygroscopic interaction and pretty pet friendly, it just makes them throw up a lot.

    OK, so I might be getting the chemical names mixed up or for that matter, I might not be even close, but: I put Syn in my little red Chevy Truck with the full blown ABS/Traction Control that required DOT 4 after a tree branch ripped the back hose off. I should have just driven back home without brakes. The cost to replace all the calipers and the master cylinder hit the four digit dollar mark real fast when the front caliper seals swelled. Oh yeah, the flat spots on the tires were a real treat as well. Can you repeat, "thumpity, thumpity, thumpity, of crap, thumpity, thumpity, thumpity", five times real fast at sixty miles an hour?
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case)
    3xR90/6, two just sold, one for a sidecar.
    1983 K100RS for winter project, two K's sold and just acquired a very rough R80RT.

  3. #3
    aapasquale
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    Quote Originally Posted by Dieselyoda View Post
    I'm sure someone will challenge my statement, seems like that is the way it is.

    I can't recall exactly the difference, been a while and I have CRAFT disease but, DOT 2-4 were polyester ethylene glycols with varying degrees of each compound. That's why if you spilled some they ate your paint and if the family dog got some, DEAD he'd be after a painful and agonizing passing.

    Synthetics are polyvinyl propylene glycols with superior properties and great resistance to hygroscopic interaction and pretty pet friendly, it just makes them throw up a lot.

    OK, so I might be getting the chemical names mixed up or for that matter, I might not be even close, but: I put Syn in my little red Chevy Truck with the full blown ABS/Traction Control that required DOT 4 after a tree branch ripped the back hose off. I should have just driven back home without brakes. The cost to replace all the calipers and the master cylinder hit the four digit dollar mark real fast when the front caliper seals swelled. Oh yeah, the flat spots on the tires were a real treat as well. Can you repeat, "thumpity, thumpity, thumpity, of crap, thumpity, thumpity, thumpity", five times real fast at sixty miles an hour?
    So, are you saying it's okay or it's not?

  4. #4
    It should be DOT 4, and it must not be DOT 5.

  5. #5
    DOT 5 is silicone based and does NOT mix with DOT 3, 4 or 5.1 which are propylene glycol based. NEVER mix silicone with glycol brake fluids under ANY circumstances. Never put either of the two in a brake system designed for the other type. The main difference between 3, 4, and 5.1 is their boiling point. You "can" mix them but I would not. What they mean by "synthetic" can vary all over the map, but IMO it is a non-issue. What matters is the performance of the brake fluid wet or dry. Wet means it has absorbed some water. IMO, I would get one brake fluid and stick to it. It isn't that critical if you have to add some other brand out on the road but try to stay with the same DOT rating if possible but again, NEVER mix silicone and glycol types. If you have to mix brands or glycol DOT ratings, change the brake the fluid and get it back to one in some reasonable amount of time.
    Old But Not Dead
    Semper Fi

  6. #6
    All brake fluid is synthetic. Labeling is marketing. Use DOT 4. Do NOT use DOT 5.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  7. #7

    This is a EZ one....

    Use what is recommended by BMW. The answer for your question is located on top of the brake reservoir.
    Don't go mixing brake fluids. You don't need to.
    Keep in mind some brake parts, (Brembo) are not rebuild able.
    Parts are not available from BMW or Brembo, U.S.A.
    Like a master cylinder kit for a 1995 R1100R.

  8. #8
    Quote Originally Posted by PGlaves View Post
    All brake fluid is synthetic. Labeling is marketing. Use DOT 4. Do NOT use DOT 5.
    Thanks!

  9. #9
    Small road corner junkie pffog's Avatar
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    Quote Originally Posted by PGlaves View Post
    All brake fluid is synthetic. Labeling is marketing. Use DOT 4. Do NOT use DOT 5.
    +1
    2010 F800GS Full Ohlins package, '04 R1100S Replika
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