The truss rod is an adjustable metal reinforcing rod that is set into the guitar neck under the fingerboard. The purpose of the truss rod is to provide additional stiffness in the guitar neck and to compensate for the tension of the strings.
If the truss rod is not adjusted correctly, the result will have a direct bearing on the action and playability of the instrument.
- Acoustic guitar truss rod adjusters are usually located inside the soundhole.
Electric guitars and basses usually have an opening at the headstock base, where the truss rod adjuster is located. However, on some earlier guitars the adjuster can be found at the body end. It should be noted that a very slight turn of the adjuster can have a dramatic effect on the action.
- Most truss rod adjusters are allen key fittings.
- Use a nut wrench on the Gibson style adjusters.
Make a quick test to see how your truss rod is adjusted. You can do this by holding the string down at the top and bottom of fingerboard. Use the string as a straight line. This will indicate how the truss rod is currently set. If it is set correctly, there will be a slight gap between the string and the frets around the half way point of the neck.
If the truss rod is too tight, the neck will assume a convex shape or negative bow, this will result in string rattle and a compromised string tone.
If the truss rod is too slack, the neck will assume a concave shape or positive bow, this will result in a high action, difficulty with fretting the string and could compromise the intonation.
Rotate to tighten or slacken. Direction of rotation will differ depending on the adjustment location and manufacturer.
Truss-rod adjustment warning here…