Episode 027: A Matter of Truss

Understanding the truss rod and how to adjust it helps you master your instrument setup. How does it work?

What is the truss rod and what does it do?

  • Usually one (occasionally two) rods inside the instrument neck, anchored at one end with an adjustment on the other
  • As you turn the adjustment (usually with an Allen wrench/hex key), it bends the rod more or less to counteract the force of the strings pulling the neck
  • Tightening the truss bends back against the strings more (“arch”), lowering action; loosening it lets the strings bend the neck more (“bow”), raising action

Where’s the truss adjustment on your bass?

  • Dave’s nice boutique bass 🙂
    • I have an app
    • Headstock behind the nut
  • Paul
    • Fender and many other basses usually have this at the joint end of the neck where it’s bolted to the body
    • With some basses you must remove the pickguard or the whole neck to adjust the truss
    • Some others, like Music Man basses, have a wheel you can turn
    • I’ve had neck-through basses that adjusted at the headstock, too

How often do you usually adjust your truss?

  • Dave
    • Definitely every couple months, but I also leave it to feel – fighting action
    • Sometimes I’ll play another bass and it’ll hit me like a ton of bricks
  • Paul
    • Several times a year, usually when seasons change or it’s been a while since I used the instrument

How to do it?

  • CAUTION: Small adjustments. Shouldn’t need more than ¼ turn for most cases, usually less
    • If the adjustment turns loosely, see a qualified repair person; the truss may be broken
    • DAVE: What does that even mean? I’ve always heard that but never understood
  • Check action by holding a finger at 1st and 14th fret, and look at clearance at 7th fret
    • For most people, should clear about the thickness of a good quality business card
    • You can get more detailed than this, with precise gauges and slightly different heights per string, but it’s an easy rule of thumb
    • DAVE: Feeler Gauge (for auto repair) at .015”
    • DAVE: Also the capo on 1st fret vs using the elbow
  • If you have to remove the neck to adjust the truss, do this order:
    • Loosen the strings to slack
    • Capo at the first fret
    • Turn over instrument and remove bolts carefully with instrument supported
    • Make adjustment, then restore and tighten bolts, remove capo and tune up to check action
  • Otherwise you may be able to adjust with the instrument in tune — but note the adjustment will detune the instrument, so you have to retune
  • If you have fret buzz at low frets on the neck, action is probably too low. If you have it at high frets, different adjustment (bridge saddles)
  • DAVE: For those out there like me, don’t be above writing notes to refer to

Photo by Glen Jackson on Unsplash

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