What Truss Rod? ALL Types & Mechanisms Explained!

What Truss Rod? ALL Types & Mechanisms Explained!

Did you know that your guitar neck is prone to bending throughout the day? This is normal for any stringed instrument and this bending is controlled by the Truss Rod! We do not see the truss because it is embedded in the guitar neck, which makes us take this simple construction for granted. However, we cannot forget that it is one of the most important parts on any guitar. It is built right into the construction of the guitar which means it can affect your tone. With careful adjustments it can increase the feel and playability making your guitar much more comfortable to play.

What is a Truss Rod? A Truss Rod is a bar of material (usually steel) that slots down the whole length of the fretboard. This bar is adjusted to alter the stability of the guitar neck against the pull of the guitar strings to ensure solid tuning and resonance.

In this article, you will learn in detail how the “Truss Rod” affects you as a guitarist. 

1. What Is A Truss Rod?

As discussed a truss rod is a metal bar that runs over the length of your guitar. The truss rod stretches from the nut (at the top of the neck) to the heel (at the bottom of the neck). Some of these are non-adjustable. However, most modern truss rods are fixed with a nut and so you can easily twist it with a spanner. This will change the tension and results in a slight change in the guitar neck angle. The truss rod is also positioned a few centimetres under the fretboard and can be accessed from two places:

  • Accessed behind the nut – the truss rod can be accessed through a small hole behind the nut. This is common on most guitars, whereby it will be covered by a small piece of wood or plastic that is sometimes held down by screws.
  • Accessed in the sound hole – On older nylon-string acoustics like the Big Baby models, you can access the truss rod through the sound hole just under the neck. You can also find this on some modern acoustics but it is less common.

As discussed a truss rod is a component of a guitar that stabilizes the forward curvature of the guitar neck. This forward curvature is called the relief, whereby it creates pressure and changes the angle of the guitar neck by the tension which is created, either pulling the neck forward or backwards.

2. Why Is A Truss Rod Important?

Guitars necks are made from wood and as we know, wood can alter its state due to atmospherical changes. This is because if there is moisture in the air it will then absorb the moisture making it expand. In the dry season when there is less moisture in the air, it will contract. These changes affect the tension of the neck. Also changing the string gauge or altering tuning can also affect the tension of the guitar neck.

The truss rod is important, as its primary function is to stabilize the neck against the tension of the strings. The guitar strings put tremendous force on the neck. This force can reach up to 180 pounds in weight. The truss rod adds pressure against the strings to counter this weight, and balance out the tension. This ensures the neck does not bend and even break from the pressure.

This is the same for both electric and acoustic guitars however, acoustic guitar tend to have a higher gauge. As you would expect the higher gauge strings add more pressure on the guitar neck.

The truss rod is also important for adjusting the relief of the guitar neck. You can either have your guitar neck bow forwards, or bowed backwards. This means that the guitar neck will be angled in either two ways (please see the image below). This overall adjusts the comfort and helps the action (discuss this in more detail below). However, the truss rod is never used to set the action, but you can use the truss rod to manipulate the improving it slightly.

It is required to have a truss rod on a guitar that has high tension strings. These are strings that are made from steel and without a truss rod the guitar neck will gradually warp and bend beyond repair. This will affect tuning stability and could even break the neck. Classical acoustics that are made from nylon strings (less tension strings) do not usually need a truss rod.

3. Truss Rod Construction

The most common material to make a truss rod is either steel or graphite. Steel is more commonly used than graphite.

Truss rods stabilise the guitar neck making it possible to construct the guitar neck from less rigid materials. This includes cheaper materials, or even materials that are manmade composites. Without a truss rod, some woods would be unable to properly handle string tension. In addition, the neck can also be made thinner, which may improve playability.

4. What Are The Locations Of The Truss Rod On A guitar?

To adjust the tension of the neck you will need to locate the bolt that is connected to the truss rod. Depending on the model of guitar, this bolt can be located in five different locations:

  • Older Fender-style truss rod location – Fender guitars with a bolt on neck requires prior removal of the pick guard you can then alter the tension using a Phillips screwdriver.
  • Newer Fender-style Truss rod locations — on the new models you will find the truss rod located behind the nut on the headstock. This can usually be adjusted by 1/8″ (3 mm).
  • Fender American elite series location – The entrance to the truss rod here would be at the base of the neck at the top of the instrument.
  • Guitars that have a set neck – if your guitar has a set neck then you will find the truss rod is under a plate behind the nut on the headstock. If you have a Gibson or Epifone then they are covered with a signature bell-shaped plate. You can adjust the rod by using a 5/16” (8 mm) or a 1/4″ (6 mm) hex adjustable truss rod nut that can be adjusted with a hex box wrench.
  • Locations of the truss rod on acoustic guitars – on acoustic guitars you can access the truss rod under the guitars body, through the sound hole, or on the headstock. These will require a 3/16″ (5 mm) allen wrench.
  • Modern guitars with a bolt neck – also include adjustment from the side of the heel of a bolt-on neck. When looking from the body of the guitar to the head, counterclockwise adjustments decrease the truss rod tension (correct an underbow) and clockwise adjustments increase the truss rod tension (correct an overbow). Special tools such as a hex nut, or allen key are required to adjust the bolt of a truss rod.

5. How Does A Truss Rod Work?

On a new instrument that has come straight from the shop/factory, the truss rod should already have been set up by the manufacturer before sale. However, this may not always be the case. If you are looking to alter your neck for minor adjustments then there is no reason why you cannot do this at your home. A modern guitars truss rod is used to add or reduce the relief in the neck, to compensate for the string tension pulling on it.

Forward Bowed Neck  

If the neck bows forward, the distance between the strings and the neck is larger which facilitates a high action. If this is the case then you want to lower the action. To do this you want to turn it counter clockwise (lefty-loosey). This means you will loosen the truss rod by turning the bolt to the left.

By doing this you will decrease the relief, this will allow the strings tension to act on the neck and create a forward bow.

Backwards Bowed Neck

If the neck bows backwards, the distance between the strings and the neck is closer which facilitates a low action. If the action is too low then you may experience fret buzz. If this is the case then it means you want to higher the action. To do this you want to turn it clockwise (righty-tighty).

This will increase the relief, and increase the action of the strings which counteracts the tension making the guitar neck move backwards thus straighten the neck, creating a backward bow.

5. Altering The Truss Rod For Better “Action”

Action is the terminology we use to determine the distance between the strings and the neck. With a good action it will generally be easier to press down on the strings to play the notes across the neck. Whilst a bad action is harder to press the strings as the strings are further away from the neck. The action comes in two forms, being high action or low action. High action means the strings are further away from the fretboard whilst low action means the strings are closer to the fret board. Generally speaking low action is preferred by guitarists as it tightens up tone and makes it easier and more comfortable to play and provides more accurate intonation as it facilitates less compensation at the bridge.

Turning the truss rod might be a step in setting the action. The truss rod can be adjusted to change the action of your strings. It is important to note that just altering the truss rod will not ultimately fix the action by itself. You will need to adjust the neck angle, nut and the saddle to get the desired result.

Furthermore, your action will likely need changing due to humidity changes, changes in tuning or a change in string gauge. These factors will naturally alter the tension of the guitar neck whereby the relief of the neck will also be adjusted as a result. To compensate for expansion or contraction in the neck you can alter the truss rod to get the desired relief of the guitar neck. However, you will need to be careful when setting the relief via the truss rod because if you attempt to correct a low-neck angle (with the strings too high off the fretboard), you could overcompensate and end up with fret buzz.

6. Relief, Neck & Truss Rod

Relief is the forward bend on the guitar neck. Relief achieved through the truss rod combines with the height of the bridge to affect the playability of the instrument. Relief is typically measured as the distance between the string and the 7th fret while holding down the first and last fret. The amount of relief many guitar manufacturers prefer for an electric guitar is about .007 inches at the 7th fret. Guitar technicians usually adjust the truss rod to give a slight relief (forward bend) to make sure the guitar strings have space to vibrate freely.

If you set your guitar to have too much relief then it can make you guitar strings feel loose and lifeless.  Whilst not enough relief can make the strings buzz on the frets.

7. Dual Action Truss Rod

Some guitars such as the Rickenbacker’s have dual truss rods that make them more stable and less susceptible to climate changes. A dual action truss rod is a modern design of truss rod whereby it is fixed in a straight channel in the wood. This makes it different from the standard truss rod because they are fixed in a curved channel. The two-way rod can warp the neck in either direction creating more or less relief if needed.

A dual action truss rod is more stable and less influenced by changes of the climate. It also has the advantage of being able to adjust the relief of the neck backwards and forwards. On a vintage style truss rod the relief can only bow the neck, which can be a hard repair if the neck needs straightening.

On the downside, some players say that dual action truss rods negatively affects the tone. This is because the weight of the second rod and the additional wood removal required for installation slightly alters the tone of your instrument.

Conclusion

In this article, we learned about the essential qualities of the truss. We learned that the truss rod is primarily responsible for stabilising your guitars tuning and that it can be adjusted. Turning the truss rod facilitates the relief of the guitar neck.

A truss rod keeps the neck straight by countering the pull of the strings and natural tendencies in the wood. When the truss rod is loosened, the neck bends slightly in response to the tension of the strings. Similarly, when tightened, the truss rod straightens the neck by resisting string tension.

We also learned that there is a common myth out there. This is that the truss rods function is to set the action of a guitar. This is not entirely true. Altering the action is a bi-product when relief of the neck is changed.

Leave a Reply