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Why is one flare nut on pre-fab brake lines longer?

Discussion in 'The Hokey Ass Message Board' started by Kevin Lee, May 11, 2011.

  1. Kevin Lee
    Joined: Nov 12, 2001
    Posts: 7,410

    Kevin Lee
    Super Moderator
    Staff Member

    Just curious to know why - it seems like every application I've seen only requires the short ones leaving a lot of threads showing on the long side.
  2. JeffreyJames
    Joined: Jun 13, 2007
    Posts: 16,612

    from SUGAR CITY

    I was wondering this a couple weeks ago.
  3. metalshapes
    Joined: Nov 18, 2002
    Posts: 10,743

    Tech Editor

    Same here...
  4. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,678


    I have asked around, nobody seems to have any idea.

  5. Craig Owens
    Joined: Jun 28, 2006
    Posts: 420

    Craig Owens

    I've been curious about that, too. I've never seen an application that calls for the long flare nut, but it forces you to buy a short one if you want your work to look neat. Maybe that's the rationale for putting that damn long nut on there.
  6. Racrdad
    Joined: Jul 27, 2007
    Posts: 1,208


    Yeah, good question! That always bugs the piss outta me trying to put that long one where it looks the least crappy.
  7. 57choptop
    Joined: Jul 24, 2009
    Posts: 31


    Yeh, what gives?
  8. caseyscustoms
    Joined: May 15, 2005
    Posts: 1,031

    from st.joe, MO

    x10. always wondered that myself
  9. on some wheel cylinder they need to be longer so you can get a wrench on them.
  10. oldolds
    Joined: Oct 18, 2010
    Posts: 3,033


    Some older cars needed the longer nut when threaded into the wheel cylinder. Every once in a while I have come across a 50's or older car that the short end bottoms out on the hex before the line is tight.
  11. brigrat
    Joined: Nov 9, 2007
    Posts: 5,281

    from Wa.St.

    I have seen the need on deeper cut M/C..........................
  12. For me the answer came easy, the long flare nut goes to the wheel cylinder, make it easier to install around all the protrusions on the backing plate. Using the shorter one at the wheel is hard to get a wrench on.

    That's my story and I'm sticking to it ;)

    What do I win?
  13. REM/Mo
    Joined: Feb 24, 2008
    Posts: 281

    from Missouri

    A lot of the larger trucks have wheel cylinders that require a long flare nut to seat in the cylinder.
  14. Dennis Lacy
    Joined: Apr 27, 2008
    Posts: 1,083

    Dennis Lacy

    One thing about the longer nuts, they support the brake lines better. If there are any sections of a brake line layout where there is a fairly long span between a line joint and a frame mounting clip the long nuts can be your friend because in this situation if a short nut were used the line would be more susceptible to a fatigue failure at the flair.
  15. You guys were faster at typing than I was :eek:
  16. it's all in the wrist
  17. bryan6902
    Joined: May 5, 2008
    Posts: 1,137


    I'll really sleep better tonight knowing this, thanks fellas!
  18. badshifter
    Joined: Apr 28, 2006
    Posts: 3,232


    I call BS, an extra 1/8 inch supports a long run better?
    low down A likes this.
  19. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 2,986

    from Dublin, OH

    I always was told that if you needed to put a coupling on a line, use the long threaded flare nut at the coupling. At least that's what I was told the long one was for.
  20. davedeltadog
    Joined: Aug 8, 2008
    Posts: 172


    The MOPAR guys know the answer, the MOPAR wheel cylinders are drilled and taped deeper therefore the nut has to be longer to seal flare.
  21. iammarvin
    Joined: Oct 7, 2009
    Posts: 1,197

    from Tulare, Ca's cheapy universal do all don't care what it looks like if it don't work throw it away oops i f ed up oh well it kinked gotta get more thank god i didn't do that in stainless made in third world country so it can be sold anywhere in the world but won't fit my applacation is either one half inch to short or two inches to long after it was bent needed the other threaded end to work better enginered product. Why else would they do that?
  22. ironpile
    Joined: Jul 3, 2005
    Posts: 915


    Some wheel cylinders,the line is difficult to get a wrench on,the longer nut makes a little easier. My 2 cents worth,only been doing it for 50 yrs.
  23. ironpile
    Joined: Jul 3, 2005
    Posts: 915


    Can`t say as I`ve ever ran into that problem but there`s always a first time.
  24. I like Marvin's answer. The simplest answer is usually right.
  25. devilleish
    Joined: Jan 15, 2007
    Posts: 251

    from Tampa, FL

    Yeah, that bleeder can get in the way fast with the short nut.
  26. Longer thread in the master cylinder necessitates a longer thread on the flare nut.

    I've never bought pre-fabbed brake lines though.
  27. RodStRace
    Joined: Dec 7, 2007
    Posts: 2,311


    Okay, but how many use a LINE on a front wheel cylinder?
    Hose, yes. Line?
    I know there are some applications where there are 2 wheel cylinders, hence a line. But how many have lines to a single wheel cylinder?
  28. Racrdad
    Joined: Jul 27, 2007
    Posts: 1,208


    I think we have a winner! :D
  29. The37Kid
    Joined: Apr 30, 2004
    Posts: 27,354


    The larger ones are easier to find after your reflare the line and note the fact that you forgot to put it on the line before reflairing.
  30. Makes the fluid flow more better

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