In my repair shop, I am often asked how often a “truss rod” should be adjusted. Unfortunately, there is no clear response for this question. The truss rod is in place in case it is needed, not because it is needed. In an ideal world, your truss rod would never require an adjustment unless your instrument has a flexible neck and you are changing string gauges. In fact, older guitars did not have these rods, and the curvature of the neck was adjusted using different methods of fretting and re-fretting the instrument. In most cases, modern guitars will have a truss rod installed to help control the curvature of the neck, and may require adjusting for many reasons.
Fortunately, the necessity to adjust your truss rod is usually accompanied by some clear symptoms. Usually, the player will begin to find that their instrument has become more difficult to play, as the curvature has increased the distance of the strings from the finger board near the middle of the neck, or in the case of the instrument’s neck having a backwards curvature or “back bow,” the player will commonly notice “buzzing” in a specific area of the neck. This is usually between frets one and five, but doesn’t necessarily have to be.
Remember that the truss rod should only be adjusted by a skilled repair technician. Adjusting the truss rod can severally damage the instrument if it is done wrong, and I have personally seen more than one neck that has cracked along the truss rod after a novice adjustment. I have even seen a truss rod break straight through the back of a neck that was built too thin.
More times than not, when a guitar comes in to have its neck adjusted there are many other problems with the instrument that the player had overlooked, or was unaware of. Bringing your guitar to a skilled repair technician or luthier for a setup will ensure that the appropriate amount of attention will be paid to your instrument. Keep in mind that simply adjusting your truss rod is not an adequate method of correcting problems with the action. A truss rod adjustment affects the action but should not be used to adjust in. In other words, the proper curvature of the neck should be set, and then attention can be paid to adjusting the action.
By David Bolla