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Technical Brake pedal question

Discussion in 'Traditional Hot Rods' started by Russ Tee, Mar 28, 2020.

  1. Russ Tee
    Joined: Sep 2, 2012
    Posts: 106

    Russ Tee
    ALLIANCE MEMBER
    from Florida

    Hey guy's, hope everybody's staying healthy. I'm plumbing the brake system on my 31 model A coupe and I have a brake pedal question. The setup is 4 wheel drum brakes, master cylinder is under the floor. My question is, should the master cylinder bottom out before the pedal hits the floor? My pedal is adjusted as high as it can go and the rod could still go about 3/16" plus or minus...BTW I've already thought about all the jokes about bottoming out and the length of the rod.

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  2. BJR
    Joined: Mar 11, 2005
    Posts: 6,773

    BJR
    Member

    Did you factor in any floor mat or carpet. It shouldn't matter but you do want to get full stroke at the floor level.
     
  3. Russ Tee
    Joined: Sep 2, 2012
    Posts: 106

    Russ Tee
    ALLIANCE MEMBER
    from Florida

    Right now it's just bare metal floor.

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  4. Phil P
    Joined: Jan 1, 2018
    Posts: 340

    Phil P
    ALLIANCE MEMBER

    egads likes this.

  5. If you are running a dual master cylinder and are counting on it as a safety feature; it needs to bottom out before the pedal hits the floor.

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  6. Russ Tee
    Joined: Sep 2, 2012
    Posts: 106

    Russ Tee
    ALLIANCE MEMBER
    from Florida

  7. Russ Tee
    Joined: Sep 2, 2012
    Posts: 106

    Russ Tee
    ALLIANCE MEMBER
    from Florida

    Thanks Rich, that makes sense.
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  8. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,400

    Mr48chev
    ALLIANCE MEMBER

    You aren't going to hurt the master cylinder if the piston does bottom out. I think that was the gist of Phil P's question yesterday about needing a stop to keep it from bottoming out.
    The spring will coil bind before the piston hits bottom in most cases. I'd worry about having all the travel I could and hope that I never needed all that travel with keeping the brakes in good shape and adjusted correctly. If the pedal goes clear to the floor when you are driving most likely you have all the sudden had a severe fluid leak and it isn't going to stop with the brake pedal alone. With a dual cylinder you should have half a brake system still working.
     
  9. A properly functioning dual master will never bottom out, in the event of a failure they are designed to bottom out. coil bind? Nope. Please understand how they work before offering bad information. Please ensure it will bottom out before you run out of pedal travel, I said it on the other thread, there is no brake pedal stops I. Oem stuff nor do they hit the floor, maybe they are on to something.


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  10. Russ Tee
    Joined: Sep 2, 2012
    Posts: 106

    Russ Tee
    ALLIANCE MEMBER
    from Florida

    Yes, I have the opposite, I'm short and like BJR stated, when I put carpet in I'll have even less. I think I can modify the pedal to get the length. Thanks for your reply.

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  11. Russ Tee
    Joined: Sep 2, 2012
    Posts: 106

    Russ Tee
    ALLIANCE MEMBER
    from Florida

    Thank you for the reply, I'll make sure I have full MC travel.

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  12. m.ralph
    Joined: Nov 6, 2009
    Posts: 512

    m.ralph
    Member

    Hi Russ Tee, if you haven't fixed your brake problem, give me a call tomorrow 713 927-9930 Ralph
     
  13. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,630

    mgtstumpy
    Member

    It needs to bottom out on MC BEFORE it's at the floor, not the other way around. What's the use of NOT having full travel in an emergency when you really need it the most. That's the law here and just common sense.
     

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