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Double truss rod help!!

Discussion in 'Hardware, Setup & Repair [BG]' started by brock29609, Mar 17, 2004.


  1. brock29609

    brock29609 4 strings, 2 wheels

    May 11, 2003
    Greenville, SC
    I know how to measure relief and how to adjust a standard Fender-type truss rod, but what do I do with this thing?

    What tool do I use? How do I do I know which one to adjust? The neck looks crooked to me, but since this bass has an "asymetrical" neck, maybe that's the way it's supposed to be. Help!

    Tobias Renegade 4
    [​IMG]
     
  2. I've worked on these a few times, and never experienced any big problems, so let me explain the process I used, and hopefully you won't have a problem either. You will need a truss rod wrench, probably about 5/16", and a stiff, precision straightedge at least 18" long to help measure the straightness of the neck, or more correctly the relief, or amount of curve. Start by tuning to pitch, and setting the straightedge on top of the frets next to the lowest string, with one end on top of the first fret. Note or measure the distance between the straightedge and the top of the seventh fret. This should be about .015 of an inch, or the thickness of a medium guitar pick. Now do the same on the other side, measuring the relief where the highest string is. The neck should be equally curved on both sides. It's hard to tell from your message exactly what your neck is like, so I'll give you the long version of a truss rod adjustment. You'll have it if you need it. You might be able to simply tweak one side or the other to get the neck right, but reading the whole thing won't hurt. The trick is to get the relief equal on the treble side and the bass side of the neck, eliminating any twist that might be present, and getting the neck relief right for your style of play. Whenever I work on a truss rod for the first time, I next take the string tension off and loosen the truss rod. This shows you what the neck looks like with no tension. Loosen the lowest string, then the highest, then the next lowest, etc. so the tension stays somewhat evenly distributed across the neck. Backing out the truss rod nuts (turning one half a turn counterclockwise, then turning the other counterclockwise, etc.) until they feel slack. (Bear in mind that many basses these days have two-way adjustable rods, and the nut won't come off, but will start bowing the neck forward (toward the strings) after you pass the slack point.) Judging from the picture you posted, it looks like you have one way rods, and the nuts should hit slack and just thread off the rods, as opposed to a two way rod where the nuts will hit slack and then start feeling tigh again as you turn counterclockwise. Many would-be repairmen and do-it-yourselfers snap their rods by trying to remove the captive nut from a two-way rod! If your nuts come off, you might decide to lubricate them with a little high grade grease, on the bearing surfaces only. This is a good time to clean and oil the board, if it needs it. With no string tension and the truss rods slack, lay a precision straightedge on the frets on both sides of the fingerboard, to see if there is any twisting in your neck. Both sides (the G side and the B or E side) should look the same when you put the straightedge on top of the frets, either equally straight or equally slightly curved in the same direction. Now that you know the natural shape of the neck with no tension, and you have cleaned the board and/or lubed the nuts, turn the nuts clockwise until they butt up against the washer at the terminus of the rod. The nuts should turn freely, until you feel them contact the block at the end of the rod. Make a note of the position of the wrench when the nuts make contact, and give them both about half a turn. An experienced hand might go a little lighter or heavier at this point, based on the shape of the neck with no tension, string type and gauge, and the players preference. NO MORE THAN ABOUT THREE QUARTERS OF A TURN! You don't want to snap a rod. If it feels tight, stop and measure! The nuts should start feeling tight pretty quickly, and if your neck is not twisted (and most are not) you want to try to get equal tension on both nuts. I use both the "measured turn" method just described and the feel of the wrench to try to get them "even." Now lay your straightedge on the frets where the highest string will lie and where the lowest string will lie. Both sides should exhibit about the same small amount of back bow. Now string it up to pitch, (I still use E/G/A/D or the equivalent to keep the stress on the neck and neck joint fairly equalized, but this may just be a function of my toilet training.) and lay the straightedge on top of the frets next to the lowest and highest strings again. The tension of the strings should pull the neck into the ballpark of the proper relief on both sides of the neck. I've never had a problem with one of those asymetrical necks, but if Michael Tobias put the two rods in there, there may be occasional twisting problems since there is more wood on the bass side of the neck and most string sets exert equal tension on both sides of the neck. The trick is to get the relief the same on both sides of the neck, hence the fine tuning possible with the two rods. It probably took longer to talk about it than it will to do it. If the relief is greater on one side than the other, tighten the rod on that side maybe an eight of a turn. If the relief is too great or too little on both sides, work back and forth across the two rods until you get the right relief on both sides. Go slowly, measuring every eigth of a turn, retuning, and letting the neck settle in after every adjustment. It might take a few hours or even a few days until everything gets settled in. Tune, measure, adjust, tune, measure, and go watch "Drowning Mona" with Danny DeVito. Then tune, measure, adjust, tune, measure, adjust, and go watch "The Big Lebowski" with what's his name. If you are drinking whiskey, leave this for another time. And don't cut yourself to death. If this seems confusing, do yourself a favor and pay a pro to do it.
     
  3. miccheck1516

    miccheck1516 Guest

    Feb 15, 2003
    Ireland
    My eyes :(

    John goodman, flea???