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size of brake lines

Discussion in 'The Hokey Ass Message Board' started by Xman, Nov 13, 2012.

  1. Xman
    Joined: Nov 17, 2011
    Posts: 455

    Xman
    Member

    Has anyone had a problem running 3/16 brake lines with 40 hyd brakes and a stock master cyl. Will there be enough volumn flow?
    input appreciated.
     
  2. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,227

    Da Tinman
    Member

    it'll be fine.
     
  3. I can only see it being a volume flow issue if the brakes are not kept adjusted up. JW
     
  4. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,241

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL


    The brake line size will not overcome maladjusted brakes. The volume required is solely a function of the master cylinder, not the "tubes" that deliver the fluid.


    Ray
     

  5. 325w
    Joined: Feb 18, 2008
    Posts: 5,686

    325w
    ALLIANCE MEMBER

    Will we ever solve this idea. Bigger is not always best.
     
  6. gatz
    Joined: Jun 2, 2011
    Posts: 1,607

    gatz
    Member

    the fluid in a 3/16" brake line will get there faster, thus ensuring quicker stops, lol.

    I was surprised to see 3/16" lines on a 67-68 Dodge rear-end.
    Don't know why I was expecting bigger. As long as there's a good conduit to the MC, it doesn't matter.
     
  7. Hnstray, i agree with that and i have 46 brakes on my T.My thoughts were of the returning fluid only due to the cylinder bore sizes and shoe return spring tentions.Cheers JW
     
  8. The main reason to run the 1/4 inch lines is that you can use all stock connectors (assuming you are running a complete '40 system).

    Charlie Stephens
     
  9. paul55
    Joined: Dec 1, 2010
    Posts: 3,490

    paul55
    Member
    from michigan

    less volume, but higher line pressure.
     
  10. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    The size of the line does not effect the pressure the master cylinder delivers to the caliper/wheel cylinder.
     
  11. 40FordGuy
    Joined: Mar 24, 2008
    Posts: 2,907

    40FordGuy
    Member

    It's about the only time that size doesn't matter .......

    4TTRUK
     
  12. flamedabone
    Joined: Aug 3, 2001
    Posts: 4,993

    flamedabone
    ALLIANCE MEMBER

    This has been the subject of bench racing for years, but the short answer is it does not matter. 3/16 or 1/4 will make ZERO diffrence in the performance of your braking system.

    I am a hydraulic technician for a living and can tell you about formulas you can use to calculate pressure and flow through lines, fittings etc as pressure and flow are inversely proportional and change with the presence of resistance. But in the end for the brakes on your hot rod, it just doesn't matter.

    Good luck, -Abone.
     
  13. paul55
    Joined: Dec 1, 2010
    Posts: 3,490

    paul55
    Member
    from michigan

    some older drum systems used 1/4" rear and 3/16" front. Using a single fruit jar cylinder, I always understood that 3/16" offered increased line pressure to engage front brakes first, then rears??
     
  14. I guess I am also a hydraulic tech as I am a fire sprinkler contractor. To push the same volume through a small pipe as a big pipe (or tube) you have to increase the velocity of the fluid. Basicly a funtion of cross sectional area. With higher velocity comes higher friction loss.

    All that said. Probably no problem. I am using 1/4 inch on my 32 cus it is old school. Did they have 3/16 brake tubing in 1963.

    Tim
     
  15. paul55
    Joined: Dec 1, 2010
    Posts: 3,490

    paul55
    Member
    from michigan

    my 55 chevy is set up as I described. Before proportioning valves, I assumed line size(pressure) was only way to change the braking system to allow for timing of braking front to rear? Anyway, good luck.
     
  16. qmdv, my 39 Willys had 3/16 lines as standard. JW
     
  17. fordor41
    Joined: Jul 2, 2008
    Posts: 960

    fordor41
    Member

    And my '41 Ford had 1/4" from factory.
     
  18. 270dodge
    Joined: Feb 11, 2012
    Posts: 742

    270dodge
    Member
    from Ohio

    I have always used the 3/16 as it's easier to bend. The size is not important. What is important in a brake system is to change the fluid about every 3 years as brake fluid absorbs water from the air and will rust the system.
     
  19. Xman
    Joined: Nov 17, 2011
    Posts: 455

    Xman
    Member

    All good input I feel better about using the 3/16 SS lines - looks better and easier to bend.
    Thanks all
     
  20. Ned Ludd
    Joined: May 15, 2009
    Posts: 4,284

    Ned Ludd
    Member

    Precisely: the principle to keep in mind here.

    The bigger the diameter, the smaller the proportion of the cross-sectional area that is subject to laminar flow. But with the sorts of displacements and velocities we're talking about I think we're all agreed it's splitting hairs.

    Of course the bigger the lines, the greater the total volume of fluid in the system. If any kind of contamination makes the fluid compressible, through cavitation or whatever, the greater the fluid volume, the greater the effect. In other words, if there are gas bubbles in the fluid it'll take more pedal travel to squash them to near-liquid if the total fluid volume is greater.
     
  21. ctc34
    Joined: Nov 1, 2012
    Posts: 26

    ctc34
    Member

    Why is everyone talking about flow volume? There is no recirculation of the hydraulic fluid in a brake system. There is a reason an application of the brakes should be instantaneous. All the way to the caliper piston the brake lines stay full of fluid assuming there are no leaks in the system. The size of the brake line will not make your system any more or less safe, and will not affect the systems performance.
     
    Last edited: Nov 14, 2012
  22. 270dodge
    Joined: Feb 11, 2012
    Posts: 742

    270dodge
    Member
    from Ohio

    Yep I'm thinkin that you could have 2 inch lines and the brake system would work the same as if it was 3/16. It's all about the volume of the master cylinder to the volume of the wheel cylinders. Or am I wrong?
     
  23. 270dodge you are correct.
     
  24. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    CutawayAl
    Member
    from MI

    That is a common belief. In a brake system, pressure is equal in in all parts of the system. Or in the case of a system with a stepped bore dual master cylinder, pressure delivery is equal in all parts of the system.
     

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