Episode 027: A Matter of Truss

Practical Bass
Practical Bass
Episode 027: A Matter of Truss
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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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