How to Adjust the Truss Neck on a Guitar

Humidity can cause the neck of a guitar to bow.

The angle of the guitar's neck influences its sound and playability. If it is bowed backward, the strings will rattle against the fretboard. If it is bowed forward, it will be difficult to make clear notes. Inside the neck is a truss rod, a metal pole that enables you to adjust the angle of the neck. It's imperative to treat truss rod adjustments with caution, as over-enthusiastic tightening or loosening can cause damage to the neck. But small, corrective adjustments can improve your guitar's playability dramatically.

Things You'll Need

• String winder (optional)
• Philips screwdriver
• Hex key

Instructions

1. 

   Look down the guitar to identify a neck bow.

   Troubleshoot the neck to determine the type of bow and the relevant corrective adjustment. Examine the neck from the side. If it is severely bowed, you will see that the neck tilts backward or forward in relation to the body of the guitar. If the distance between string and fretboard increases greatly on the higher frets, this is a symptom of a forward-bow. If a visual examination throws no light on what kind of bow you have, play the guitar. Play the first three frets of the G, B and top E string. If the neck is bowed backward, there will be insufficient space between the strings and top frets, and these frets will buzz when played.

2. 

   Use a string winder to speed things up, if you have one.

   Relax the tension of the strings. You don't need to totally remove them, but slacken them to the point where they apply no tension on the neck.

3. 

   The truss rod is located under this bell-shaped shield.

   Find the correct end of the truss rod. Some truss rods protrude into the headstock; others protrude from the bottom of the neck. If you can't see the truss rod nut under the bottom of the neck, it is at the other end. Sometimes there is a truss rod cover on the headstock. Remove the truss rod cover by unscrewing it with a Philips screwdriver.

4. Insert the hex key. Tighten the truss rod to correct a backward bow and loosen it to correct a forward bow. If adjusting from the headstock, turn the hex key clockwise to tighten it and counterclockwise to loosen it. Do the reverse if tighten the other end of the rod. Adjust by no more than a quarter of a revolution at a time.

5. Tune the strings. Getting the angle of the neck right is a delicate balancing act, because the string tension compensates against the truss rod tension. When correcting a back bow, you won't know if you've sufficiently adjusted the rod until the strings are full tension because they will "pull" the neck slightly.

6. Readjust the truss rod, if necessary. If the neck is still bowed when the strings are tuned, loosen the strings and make another quarter-revolution truss rod adjustment.

Tips & Warnings

• If you hear a creaking sound, stop adjusting the truss rod.

References

• Internet Guitar Database: Guitar Truss Rod Adjustment
• Ultimate Guitar Online: Truss Rod Adjustment