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Technical 4 Wheel Disc Brake question.

Discussion in 'The Hokey Ass Message Board' started by lrs30, May 23, 2019.

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  1. lilmann
    Joined: Apr 13, 2017
    Posts: 145

    lilmann

    Ahhh ok, thanks!


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  2. Do it Over
    Joined: Dec 25, 2017
    Posts: 478

    Do it Over
    Member
    from NYC, NY

    The seal position on the piston the the fluid holes in the master determines when hyd pressure moves. This is what determines when and which brakes are applied not the proportioning valve.
     
  3. I personally have never seen one where the seal wasn’t directly next to the vent port, next to that you are mostly correct in that the proportioning valve does not determine when and which brakes it proportions rear brake application, pressure rise is equal front to back until the split point of the proportioning valve then the rear rises at a slower rate. This is because of the self energization of servo acting brakes, we never want the rear to lock up first


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  4. pbr40
    Joined: Aug 10, 2008
    Posts: 874

    pbr40
    Member
    from NW Indiana

    When using a adjustable proportioning valve what pressure do you set the back at?
     
  5. Doublepumper
    Joined: Jun 26, 2016
    Posts: 1,535

    Doublepumper
    Member
    from WA-OR, USA

    It varies. I start with them completely open, then (if needed) start incrementally closing them off until the rear brakes stop locking up prematurely.
     
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  6. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,966

    V8 Bob
    ALLIANCE MEMBER

    I also agree to start with the valves full open (max rear pressure) to simplify initial braking evaluation. If the rears are "lazy" while testing, a larger wheel cylinder or brake (more rear braking) is needed. Conversely, If the rears are too aggressive with the valve adjusted all the way to the low side, less rear brake is needed.
    Any testing should be done after the brakes are "beded" or burnished.
     
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  7. pbr40
    Joined: Aug 10, 2008
    Posts: 874

    pbr40
    Member
    from NW Indiana

    Thank you gentlemen! I was unsure if there is a scientific mathematical number that needs hit! Thanks
     
  8. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,802

    jimmy six
    ALLIANCE MEMBER

    Not sure on disc- disc, but my non power disc-drum has 7/8" MC. Mine is a Wilwood but I was told no power has a smaller diameter bore than power. My brakes act like power from the old drum-drum. Fronts are 4 piston and not single with a floater. Good luck.
     
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