Adjusting the truss rod of an acoustic guitar isn’t hard, but it does affect the guitar’s sound quality. You will use a nut wrench to grab the threading of the rod and turn it in minuscule increments to either tighten or loosen it. Such action will cause the neck to bend forward or backward.
This will help position the neck so the strings deliver optimal play. Where its final spot will mostly come from your personal preferences. However, you must take great care to avoid bending the neck too far back.
What Is A Truss Rod?
The truss rod is a small metal pole situated snugly in the center of the guitar’s neck. It requires adjusting from time to time due to long-term playing, changing string gauges, or increases in environmental humidity, among others.
How Does It Work?
The truss rod of an acoustic guitar braces the inside of the neck to help withstand the tension and pressure put on by metal strings. These are usually adjustable to make the neck bend back (back bow) or forward (upbow). The truss rod keeps strings taught and at an optimal curvature for the best sounds possible.
Where Is It On An Acoustic Guitar?
The truss rod on an acoustic guitar nestles within the center of the neck. One end comes threaded for adjusting, which you can access through either the soundhole or headstock. The other end of the truss rod serves as an anchor for tightening.
Acoustic guitars have two types of truss rods you can adjust. The first is single-action or one way and the other is double-action or two way. One way truss rods straighten the neck against the tension of the string and upbow. Two-way truss rods also straighten the neck but also force a back bowed neck either straight or into an upbow.
How To Tell If A Truss Rod Needs Adjusting?
Determining if the truss rod needs adjusting will depend on if the guitar is new or if it has already been in your possession. When brand new, many manufacturers ship the guitar with a severe upbow, making the strings high-pitched. This is so the owner can lower it to their preferences and tastes.
If you’ve had your guitar for a while, you’ll know the truss needs adjusting when the neck has too much or too little backbow or upbow. But, there are three primary indicators that the truss rod needs adjustment.
String Action Is Off
One indicator is when you notice a significant change in the string’s action and the strings’ height over the frets are either too low or far too high. Often, strings will get much higher due to an upbow for how the strings pull on the neck. There will be a slight curvature forward.
Buzzing or Muted
The second indicator is that there may be a buzzing sound emanating from the frets between the fifth fret and the nut. Or, it could be entirely mute, also known as “fretted.” This means the neck is too straight or it has a backbow from the truss rod.
If you are still unsure, you can do a little test and this is the third indicator. As you press down at the 1st and 14th frets, the string should be about .010 inches away from the 6th fret. This is the same thickness as a business card.
When there’s more distance than there should be, then the neck bends forward. If there isn’t space at all, then it’s bending backward. While both are serious issues, this latter situation will require adjusting the truss rod ASAP. You do not want a neck that bends backward.
Tightening And Loosening
When you go to tighten or loosen a truss rod, always remember righty tighty, lefty loosey. But, this will depend on your orientation in relation to the guitar and how you’re able to access the truss rod.
Sound Hole Access
Most acoustic guitars give access to the truss rod from inside the sound hole. Righty-tighty/lefty-loosey will come into play because you’re at the end of the guitar’s body. You’ll pull up the wrench to tighten or push down to loosen.
But, if the guitar is resting in the playing position, the concept reverses: lefty-tighty/righty-loosey. You’ll push the wrench handle down to tighten or pull it up to loosen the truss rod.
If your truss rod adjustment comes from the headstock, then the same righty-tighty/lefty-loosey rules will apply depending on the guitar’s orientation. This will have an access hole in the center of the head with a truss rod cover you will have remove before adjusting.
Turn in Small Increments
Regardless of whether you’re tightening or loosening the truss rod, always work in small, incremental turns. You never want to move more than ⅛ or ¹⁄₁₆ of a turn. Check the string after each turn with a tuner in hand.
Let the Rod Settle
When you have the truss rod where you want it, allow the guitar to rest for a day or two. This will allow the neck to settle into its new adjustment. While you can play the guitar, the full effect of adjustment won’t take hold until the next day. Plus, it may not be where you want or where you thought you put it.
This means it may end up too high or low and will once again require an adjustment. Therefore, even though you can play your guitar right after adjusting the truss rod, you may end up in a vicious cycle. So, it’s best to let the guitar rest.
Adjusting the truss rod isn’t difficult and it will be necessary on occasion. But, you have to be deliberate and allow the guitar settling time. This may be tricky for newer guitars, but you will become more familiar with how it goes for quicker adjustment so you can get back to what’s important: playing.