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Technical pedal ratio

Discussion in 'The Hokey Ass Message Board' started by gregsmy, May 22, 2020.

  1. gregsmy
    Joined: Feb 11, 2011
    Posts: 58

    gregsmy
    Member
    from Florida

    I have a firewall mounted brake pedal setup that the po mounted up kinda high. It actually works out ok with the firewall and engine placement but the pedal is to high off the floor. I understand about maintaining the correct pedal ratio. I need to add about 3" to the length of the pedal and will need to lower the master cylinder pivot point to maintain the same ratio. Since the mc pivot is going to be lower, then the actuating rod is going to be on an angle instead of straight into the mc. Is there any issue with creating an offset mc rod to keep it straight and level? Sorta like a Z? To eliminate any flex I was thinking of using a short piece of flat bar with a hole drilled in the lower corner that would attach to the brake pedal. Then weld a long coupling nut to the top edge for the mc rod to thread into.
     
  2. Never2old
    Joined: Oct 14, 2010
    Posts: 709

    Never2old
    Member
    from so cal

    Pictures....


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  3. You can just extend the pedal just be aware that the brakes will get more sensitive as in you won’t have to push as hard with a greater pedal ratio than you have now. What is the current ratio and is it power or manual?


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  4. gregsmy
    Joined: Feb 11, 2011
    Posts: 58

    gregsmy
    Member
    from Florida

    It has power brakes. Current setup is right at 5:1 and it looks like it would move to 6:1 or a little more. Appears to be a factory pedal assembly from a later model car/truck.
     

  5. I would be tempted to extend the pedal and try it, before re-engineering the whole setup


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  6. gregsmy
    Joined: Feb 11, 2011
    Posts: 58

    gregsmy
    Member
    from Florida

    In the whole scheme of things, the only part I would be re-engineering would be the mc push rod. I guess I should take it apart and try to mock it up before I do any building. I found where its allowed to be up to 5 degrees inclined. I am spit-balling that it will be more than that.
     
  7. gregsmy
    Joined: Feb 11, 2011
    Posts: 58

    gregsmy
    Member
    from Florida

    Just did some searching on offset mc push rods on here and found a bunch of good info. Thanks
     
  8. hoop
    Joined: Mar 21, 2007
    Posts: 598

    hoop
    Member

    I had the same problem in my 39 Buick Extended the pedal quite a bit. You could not tell anything was different when braking. I agree with 57 Fargo
     
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  9. 48stude
    Joined: Jul 31, 2004
    Posts: 1,175

    48stude
    Member

    I lengthened my brake pedal arm 3 " on my avatar . It's a power set up from a OT 77 Chevy Caprice. Works fine. Bill
     
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  10. BJR
    Joined: Mar 11, 2005
    Posts: 6,837

    BJR
    Member

    I have extended the pedals in a car I built years ago, and it worked just fine. You would get into trouble with a very hard pedal if you shortened the the pedal arm. Go for it, if too sensitive you can re engineer it, but try it first just with the added length. Why make more work for yourself if not needed?
     
  11. 48stude
    Joined: Jul 31, 2004
    Posts: 1,175

    48stude
    Member

    This is how I extend my pedal arms. I chamfer all the areas to be welded. Bill
    Scan_20200523 (2).png
     
  12. gregsmy
    Joined: Feb 11, 2011
    Posts: 58

    gregsmy
    Member
    from Florida

    Thanks for the information. I will just lengthen it first and adjust as needed if it doesn’t feel right. I was thinking of cutting it on a long angle and fitting the extra piece in, but your way looks good to.
     

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