Guitar-Truss-Rod

Truss Rod Types? ALL Mechanisms & Construction 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. With careful adjustments, it can improve your tone and playability! Making your guitar much more comfortable to play.

What are the different types of truss rods? There are THREE types of Truss Rods. These include a Single-action truss rod, double-action truss rod, and non-adjustable truss rod.

In this article, you will learn in detail how the “different types of Truss Rod” affects you as a guitarist. So, let’s jump right in!

1. What Is A Truss Rod?

Before we go into detail about the different types of truss rods, let’s first get on the same page and understand what they actually do.

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

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 shape of the truss rod, which alters the tension and ultimately results in a slight change in the guitar neck angle.

2. Why Is A Truss Rod Important?

The truss rod is important as it counteracts the tension created by the guitar strings. Guitar strings put tremendous force on the wood of the guitar neck. This force can reach up to 180 pounds and is enough force to break the neck. With clever adjustments you can take the weight off the guitar neck and have full control of the necks shape and alignment with other parts of the guitar.

Without a truss rod the guitar neck will gradually warp and bend beyond repair. This is the same for both electric and acoustic guitars however, acoustic guitar tends to have a higher gauge. As you would expect the higher gauge strings add more pressure on the guitar neck.

In addition, truss rod can actually break the guitar if the wrong alterations are made. Truss rods are made from Iron and steel which make them stronger than the guitar itself. So, if you altering them the wrong way you can create additional tension.

3. What Are The Different Types Of Truss Rods?

There are three kinds of truss rods: These include,

  • Single action truss rod
  • Dual action
  • None-adjustable Truss Rod

We will discuss each of these below…

SINGLE ACTION TRUSS ROD 

The single action truss rod (also known as the one-way truss rod) is designed to correct the neck against the pulling tension cause by the strings. This particular design moves in one direction, correcting any forward-bowing caused from the tension of the strings. Depending how much tension is present the shape of the neck can be adjusted by tightening or loosening the truss rod screw. However, by only being able to move in one-direction the single-action truss rod cannot bend back on itself, thus addition relief cannot be created. Which can be a hard repair if the neck needs straightening. This is required in some situations, if the string pull isn’t strong enough to create a bow, a single action rod can’t synthetically create one.

This type of truss rods is only threaded on one side while the apposing side is fixed without sort of adjustability. The single-action truss rod is designed to be inserted into a curved or straight channel. One of the two ends of the truss rod is fitted with a hook or receive an anchor bolt and being bent into an L shape. While the other end will be threaded and receive an adjustment nut and washer. When the one-way truss rod is tightened at the nut, it creates forces working against the tension of the strings. This apposing tension will begin to straighten the neck. Therefore, creating a back-bow, where the forward-bow will eventually be relieved.

DUAL ACTION TRUSS ROD

Some guitars such as the Rickenbacker’s have dual-action truss rods.

A dual-action truss (also known as the two-way truss rod) are widely used on modern guitars for its convenience in having full control of the angle of the neck. This is being able to make the neck angle straight or with a slight bow (concave or convex) by being able to adjust the relief of the neck backward and forwards. This will be placed in a straight channel, and overall more stable and less influenced by changes in the climate.

Thie dual action truss rod is threaded on both sides, one end will have a left thread and the remaining has a right thread, with a fixed metal bar alongside the length. Moreover, both of the ends are fitted with nuts. It is easily bent to create a back bow or forward bow as you want. As the truss rod is tightened, it will create a hump, eventually generating a backward bowing effect, eliminating relief in the end. By contrast, if you choose to loosen the rod, you will create relief leading to a concave bow.

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 alter the tone of your instrument.

NONE-ADJUSTABLE TRUSS ROD

A single-action truss rod (also known as a traditional truss rod) is the most basic type of truss rod. It has one specific function only, which is to counteract the tension from the string pull (thus, taking the pressure off the neck).

The single-action truss rod simply helps counter the string pull!

The non-adjustable truss rods are quite obviously none-adjustable. You are not able to temper and customize the tension of the neck. 

These are used in low-end beginner type of guitar on a very cheap scale. 

This will affect tuning stability and could even break the neck. However, Classical acoustics that are made from nylon strings (less tension strings) do not usually need a truss rod.

4. Where To Access The Truss Rod On The Guitar?

The truss rod is also positioned a few centimeters under the fretboard. 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 Eight different locations:

  • 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 soundhole – On older nylon-string acoustics like the Big Baby models, you can access the truss rod through the soundhole just under the neck. You can also find this on some modern acoustics but it is less common.
  • 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 (making truss rod adjustments)?

As discussed a truss rod is a component of a guitar that stabilizes the forward curvature of the guitar neck caused by the tension from the guitar strings. This forward curvature is called the relief, whereby it creates pressure and changes the angle of the guitar neck by the tension pulling the neck forward or backwards. The truss rod will counter action this tension, and with clever luthering we can control the shape of the neck.

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.

You can control the relief creating either a concave or convex shape…

Straight Neck

The first basic neck shape we discuss is the straight neck. This is most preferred shape to have. But, if your guitar is not set up correctly you will find that it has a bend in the neck.

Truss Rod Types? ALL Mechanisms & Construction Explained!

These bends are described as either being concave or convex. We discuss about these below…

FORWARD BOWED NECK  (CONCAVE)

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 and you want to lower the action you would turn the truss rod screw clockwise (tighten). By doing this you will decrease the relief, this will allow the strings tension to act on the neck and create a forward bow.

Truss Rod Types? ALL Mechanisms & Construction Explained!

If you loosen the thread at the end of the truss rod it curves the neck inwards making it concave (creating higher action). This creates a bow / up-bow / forward bow effect. If you want more concave curvature you will increase the relief by turning the truss rod counter clock-wise (turning the truss rod to the left).

BACKWARDS BOWED NECK (CONCAVE)

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 the truss rod counter-clockwise (lefty loosey). This will increase the relief, and decrease the action of the strings.

Truss Rod Types? ALL Mechanisms & Construction Explained!

If you tighten the truss rod it will curve the neck outwards making it convex (creating lower action). This creates a backward bow / hump neck. You get this effect by reducing the relief by turning the truss rod clockwise (turning the truss rod to the right

RELIEF

The truss rod is 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.

Increasing the Relief is the process of adding more forward bow on the guitar neck. Whilst decreasing the relief is the process of adding more backward bow. If the guitar neck is too much hump (or too much backward bow), you would say that you would like to increase the relief when making these adjustments.

You can use these terminologies interchangeably which can cause some confusion. 

6. Adjusting the Truss Rod

how to adjust the truss rod relief

7. What is the Preferred Angle Of The Truss Rod?

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.

This overall adjust 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.

8. 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.

8. Truss Rod Side Adjustment For Easier Access

Over a year period your guitar neck will begin to warp and change shape naturally due to environmental changes. So accessing the truss rod can be a bit of a pain if you are wanting to make quick adjustments.

Luckily, you can get side adjustment extension whereby the truss rod can be altered from under the fretboard. However, make sure you do not let any unexperienced mess this as they have the potential to permanently ruin your guitar.

9. Atmospherical Changes

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.

10. Reduce Overall Manufacturing Costs

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.

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.

If you liked this article and you feel it helped you then please leave a comment and share it with someone who might find it useful. I am actively updating these articles daily and so I will see any comments made within a few days of posting!

You can also visit Parts Of A Guitar? If you want to find more relevant posts to read.

Thank you so much and have a great day!

Leave a Reply