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Adjusting the Truss Rod

The strings of a guitar exert a tremendous pressure on the neck. As tuning knobs are turned to tighten strings, the increasing tension tends to force the neck to curve away from the strings. The effect is similar to stringing a bow for archery. The major difference is that a guitar neck has a truss rod inside to resist the pressure for curvature. Over years, the neck alignment can change, and you can detect change visually and by feel. If low action playability has suffered and more pressure is required to fret the strings, the problem could be neck alignment. Hold the guitar so that you can see the clearance between strings and frets down the entire scale. If the neck appears to be either curving away ("cupping") or too close to the strings in the middle, the truss rod needs adjustment.

Most quality guitars have a truss rod which allows adjustment of the neck. The rod may be accessed either under the truss rod cover on the headstock, or on the base of the neck. The rod assembly is a metal rod inside a plastic sleeve. The rod is threaded at the top end and has a nut which can be tightened or loosened. Tightening the nut in effect shortens the rod and pulls the neck closer to the strings.

Loosening the nut makes the rod longer, and the neck clearance from the strings increases.

Adjustment should be made only when necessary. The result of proper adjustments will be a perfect neck alignment for the life of the instrument.

Gibson Truss Rod Information