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Basses with single action truss rods

Discussion in 'Basses [BG]' started by Hollow Man, Apr 4, 2006.

  1. Hollow Man

    Hollow Man Supporting Member

    Apr 28, 2003
    Springfield, VA
    I'm looking into purchasing a bass that has a single-action truss rod, which by my understanding, means that it will only turn in one direction. Specifically, it will only tighten, thereby pushing the neck away from the tension that the strings are applying.

    I've never owned a bass that didn't have a dual action truss rod, and I'm a little concerned that I'd miss it. I don't do a great deal of fiddling with my truss rods, but every once in a while (particularly after a string change in which I opt for different gauges), I do find the need to loosen the truss rod to add relief to the neck. What I want to know is, how big of a deal is a dual action truss rod to you folks when you're buying a bass? For those of you who own basses with single action truss rods, do you approach setting up the instrument any differently? Any information would be great... I'd like to hear other opinions to help decide if a single action truss rod is a deal-breaker for me or not.
  2. Figjam


    Aug 5, 2003
    Boston, MA
    I thought that this was how most truss rods are. They only tighten, and loosen. Dual action means that not only do they loosen, they apply pressure the opposite way. No?
  3. Brian Barrett

    Brian Barrett

    Nov 25, 2001
    Murfreesboro, TN (Nashville)
    Dealer LowEndBassShop.com, Builder LowEndBasses.com
    Hollow Man, I think there is some confusion on this truss rod issue. A dual action truss rod would actual help your issues and most builders use single action truss rods, not dual action. Sometimes there can be an issue with a single action truss rod because the string's might not have enough tension to pull the neck forward even if the truss rod is loose. In this case a dual action truss rod can be turn to apply pressure to give the neck relief, but this requires a dual action, not a single action.

  4. Navybass


    Mar 12, 2005
    Norfolk, Va.
    Single action truss rods mean that they will only straighten a neck that's bowing away from the strings. If the neck is bowing toward the strings then you can just loosen the rod and hope the string tension will bend it back and give a bit of relief.

    Now, Dual action truss rods will correct both.

    Very simple explanation.
  5. paul n

    paul n

    May 6, 2005
    Arden, NC
    Singel action rods can be loosened, it's just a simpler system than a double action rod. A double action rod will exert force on the neck in both directions. If for some reason your bass's neck is back bowed and the tension of the strings isn't enough to pull it forward (ie it's warped) then a double action rod will be able to push it forward. Of course that only works out asuming the neck is warped straight back with no twist. A double action can't fix that. I actually have aguitar with this problem, the neck is bowed straight back and it has a single action rod, so it's unplayable unless I put really heavy strings on it. The tension of the average bass string though, should be enough to keep a neck from pulling back.

    A single action rod only pulls against the tension of the strings, but you can adjust the amount of tension against the strings. When you tighten the rods nut the rod pulls the neck back against the pull of the strings. When you loosen the nut, it alows the tension of the strings to pull the neck forward.

    Hope thos helps

    ~Paul :)
  6. Brian Barrett

    Brian Barrett

    Nov 25, 2001
    Murfreesboro, TN (Nashville)
    Dealer LowEndBassShop.com, Builder LowEndBasses.com
    good explanations, but keep in mind that because a neck is bowing backwards doesn't mean its warped just like at different times you might have to adjust the truss rod because at some point the neck might need more tension or less to correct the neck. Its not warping on you, just moving. Different humidity and temperature will move the neck.

    A dual action truss rod also comes in handy if you Dtune a bass and don't use standard string tension or on short scale basses that don't have the length of the neck and tension of the string's like a 34, 35, etc.
  7. Audere

    Audere Supporting Member Commercial User

    Apr 7, 2005
    South Beach, OR
    Owner: Audere Audio
    On a well constructed bass it will not matter.

    If you are looking at a specific bass (maybe a custom) - you could loosen the strings and the truss rod. Some Luthiers think the neck should be flat or maybe have some relief in this condition. This would allow the truss rod to be adjusted to countering the bow created by the strings tension to the player's preference.
  8. Hollow Man

    Hollow Man Supporting Member

    Apr 28, 2003
    Springfield, VA
    Thanks everyone... it sounds like I just totally misunderstood what 'single action' meant in terms of function. I thought that it implied that it would only effectively turn in one direction, as opposed to only being able to apply pressure in one direction. As it turns out, I'm quite familiar with single action truss rods, and I've never had a problem with them. Thanks for straightening me out (no pun intended)!
  9. 7flat5


    Nov 28, 2003
    Upstate NY
    One more clarification here. Well-designed necks with single-action truss rods are made so that they have a little back-bow when strings are not installed, but some relief by default when under string tension. The truss rod then pulls the neck back to straight to counteract the string tension. Necks with dual-action (I think of them as push-pull) truss rods are built to be absolutely straight under no tension. The truss rod can then do whatever it needs to do, add or take away relief, after string tension is applied. This is somewhat of an over-simplification as luthier magic is applied depending on the neck wood, construction, etc., The point is that the wood construction is also different depending on the style of truss rod the neck is designed for. You don't just put any kind of truss rod in any neck, the neck construction and truss rod are a system.

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