What is a Truss Rod on a Guitar and Why is it Important?

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Want to learn the ins and outs of the guitar truss rod and what it can do for you? Then step right up as we have an in-depth introduction to this most sacred of guitar parts for you today.

Introduction to the Truss Rod

The truss rod is a component of a guitar or other stringed instrument that stabilizes the lengthwise forward curvature (also called relief) of the neck. Usually, it is a steel bar or rod that runs through the inside of the neck, beneath the fingerboard.

Some are non-adjustable, but most modern truss rods have a nut at one or both ends that adjusts its tension. The first truss rod patent was applied for by Thaddeus McHugh, an employee of the Gibson company in 1921, though the idea of a “truss rod” appeared in patents as early as 1908.

The truss rod is one of the simplest parts of the guitar, and also one of the most important. Any budding musician who wants to invest in a guitar, whether acoustic or electric, should have at least a basic understanding of what a truss rod does, how it works, and what you can do with it to improve the feel and sound of your guitar.

StewMac Hot Rod Low Profile 2-Way Truss Rod, 4mm Allen Nut, 18" Overall Length

Types of Truss Rod

Now that we know what a truss rod is for, we can have a look at two of the main varieties of truss rods available today.

  • Single-Action (Compression Rod): this type of truss rod usually consists of a single piece of steel that is threaded on one end to receive an adjustment nut and washer, and on the other end, it may be threaded on one side to receive an anchor bolt or bent into an L-shape.
    • This type of truss rod can only bend the neck back and can not induce a forward bow like some other types.f
  • Dual-Action (Two-Way): comes in several different forms, all sharing one thing in common, the addition of a second rod or metal bar above the main truss rod.
    • The top bar is somehow fixed in length, and the lower bar is threaded on each end to allow it to expand or contract in length, based on which direction the nut is turned while adjusting the truss rod.

The wood in the neck itself functions as part of the truss rod system with the single-action truss rod. The nut is tightened against the wood. If the wood expands because the humidity increases, that’s equivalent to tightening the nut on the truss rod and can cause the neck to move. Most of the time, these movements are subtle.

Still, when the guitar has very low action, it can be quite noticeable to a discerning player if the humidity fluctuates a great deal and could even lead to annoying fret buzz or high action, depending on the humidity level present.

Not only that but because wood is always different in density and strength, with a truss rod that relies on the wood itself as part of the system, the neck’s stability becomes a bit of a gamble. If the wood near the adjustment nut starts to crush under pressure, it can become impossible to make any adjustments to the neck.

The Function of a Truss Rod

Sure, we get what a truss rod is for – more or less, anyhow – but what exactly is the big deal? Why is it so highly considered among the parts of a guitar?

The truss rod’s primary function in both electric and acoustic steel-string guitars is to stabilize the neck against the tension of the strings, which exerts a great deal of force on the guitar. The truss rod is there to balance out that tension so that the neck doesn’t bend from the pressure.

A common myth about the truss rod is that its function is to set the action of a guitar, which isn’t strictly true.

Action, which refers to the distance between the strings and the neck is often the first thing a seasoned guitarist will test when playing a new guitar. Turning the truss rod might be a step in setting the action, but it won’t “fix” the entire neck – you may need to adjust the neck angle or the saddle to get the action just right all the way down the neck.

If, say, you attempt to use the truss rod to correct a low neck angle (with the strings too high off the fretboard), you could overcompensate and end up with fret buzz.

Maintenance: Significance of Truss Rod Adjustment

Indeed, the ability of a guitarist to adjust their truss rod cannot be overstated.

In practical terms, the truss rod becomes most important when a player needs to adjust the relief of their guitar’s neck to suit their playing style. This is a stylistic choice that depends on the player’s technique—there’s no one right setting for every player.

A truss rod works by bending forward or backward inside the guitar’s neck when the adjustment nut is tightened or loosened. On the most basic level, it can help to counteract the guitar strings’ pull as they will cause the neck to bow forward when they are tuned up to pitch.

But having a perfectly straight guitar neck is not optimal either. Having a very subtle forward bow to the neck is optimal for low and comfortable string action/The truss rod helps subtly adjust the neck bow to find a perfect balance and the sweet spot of playing comfortably, alongside fostering a great-sounding guitar.

How to Adjust a Truss Rod

You’ll no doubt now be gasping for a chance to adjust your own truss rod. Follow the instructions below to find out how (or follow these instructions to do it to an acoustic):

  1. Open up the truss rod cover.
    • The adjustment nut can be in one of two places, at the headstock end or at the body end.
  2. Fix and tune your strings.
    • It’s time to fit your chosen pack of strings and wind them up to the tuning you’re after.
  3. Attach the two capos at the 1st and 15th frets.
    • This allows you to use the string as a straight edge which will show up the curvature in the neck.
  4. Measure the gap between the string and the fret top at the 6th and 7th fret.
  5. Turn your truss rod adjuster nut clockwise and you will add more pressure onto the neck pulling it into a back bow. Turn it anti-clockwise and you will loosen the truss rod allowing the strings to pull the neck into a forward bow.
    • Some forward bow is needed for sure.
  6. Use your feeler gauges to get the correct bow on the neck.
    • You can’t have a flat truss rod setting because the string vibrates in an elliptical pattern, we need to mirror this to some degree. Use the 0.006-inch (0.15mm) to 0.012-inch (0.30mm) feeler gauges for this.
  7. There you have it!

Installing and Replacing a Truss Rod

Of course, sometimes our truss rods are simply no longer up to the task, in which case they might be better off being replaced like so:

  1. Lay the instrument on a flat, stable surface.
  2. Take the strings off the instrument.
  3. Melt the fretboard glue with an iron starting from the head.
  4. Slip a flat putty knife underneath the fretboard.
  5. Work down the neck with the knife and iron to pry the fretboard up.
  6. Pull the fretboard off when it comes loose.
  7. Scrape away any glue holding the old truss rod in.
  8. Remove the old truss rod.
  9. Clean any glue out of the truss rod channel.
  10. Sand the old glue off of the neck.
  11. Vacuum the neck to remove any sawdust.
  12. Get a truss rod designed for your instrument.
  13. Fit the new truss rod into the channel with the nut facing the neck.
  14. Cover the rod with a strip of masking tape to protect it from the glue.
  15. Run a strip of wood glue around the perimeter of the guitar neck.
  16. Spread the glue out into a thin layer.
  17. Press the fretboard onto the neck.
  18. Clamp the fretboard down to let the glue set for one hour.
  19. Finally, scrape off any glue spillage around the neck.

Common Issues with the Truss Rod

The major problems caused by truss rod nuts in an electric guitar can be narrowed down to three factors:

  1. Defective hardware: though not common, a high volume production could be blamed
  2. Worn-out tools: don’t use force to aggravate the damage
  3. Previously failed adjustment using a wrong-sized tool: caused loose grip

 So, even before attempting to manipulate any parts of the electric guitar, we need to check our toolkit to ensure that we do have the correct tools. The sharpness and precision of the tool are very important to avoid further harm if used forcibly. Use the correct type and size of tools to repair your electric guitar as it may turn out to be more expensive to salvage the damage caused by old incorrect tools.  

Impact of the Truss Rod on Guitar Tone

It is the belief of some that a tighter truss rod will produce a brighter tone, though it’s hard to see how the truss rod could affect the guitar beyond playability and the obvious signs of fret buzz across the length of the fretboard.

Sure, it may have something of an effect, but such an effect will be microscopic and will, thus, largely be the preserve of basement-dwelling veterans with too much time on their hands.

Choosing the Right Truss Rod for Your Guitar

Let’s take a look at some of the pros and cons of the two main types of truss rods so you can make your own mind up. First, the pros of the single-action truss rod:

  • Lightweight
  • More wood left in the neck

And the cons:

  • Affected greatly by variations in wood density
  • No forward adjustment
  • More affected by relative humidity

And, now for the cons of the dual-action truss rod:

  • Not dependent on wood density
  • Two-way adjustment (forward and back)
  • More stable than a single compression rod

And the cons:

  • Weighs more
  • Requires more wood to be removed
  • The adjusting nut is attached and if damaged can not be replaced

Conclusion: The Significance of the Truss Rod

A guitar neck made of wood is prone to bending due mainly to atmospheric changes, and the pull created by changing to a different gauge of guitar strings and/or different tuning. Though a similar effect could be achieved with a roasted maple neck, truss rods are still used for precise adjustments. A truss rod keeps the neck straight by countering the pull of the strings and natural tendencies in the wood.

That’s it! If adjusting your truss rod doesn’t solve your problem, it’s wise to bring your guitar to an experienced tech or luthier rather than tinkering away at it yourself, especially if you don’t know what you’re doing!

Hopefully, you have learned something of your own today and can take this learning out into the world with you wherever you go!

FAQs Truss Rod

Which way do I turn the truss rod to lower action?

Decrease relief tightening of the truss rod by turning it clockwise influences the neck to curve upward toward the strings (convex). Increase the relief loosening of the truss rod by turning it counter-clockwise influences the neck to pull away from the strings (concave).

When should I tighten my truss rod?

With a truss rod that is functioning properly, there are only two things that might require the neck to be adjusted: a) a change in string gauge (higher or lower tension) or b) a change in weather humidity (which can cause the neck to expand or contract).

Will tightening the truss rod lower action?

Any adjustment of the truss rod will affect the action, but it is not the “action adjustment” for a guitar. It can fix certain problems with the action, but the effects will not be the same all the way along the fretboard. It will not in general make the action higher or lower.

Is a truss rod necessary for beginners?

Yes, it is necessary for every guitar to have a truss rod except for classical guitars. The truss rod is there to help you adjust the guitar to your liking and also to keep the action low enough to make it playable. If the guitar doesn’t have a truss rod don’t buy it. Guitar necks and notoriously prone to bending.

By Nate Pallesen

Nate is just your average (above average) guitar player. He's no Joe Satriani, Jimi Hendrix or Jimmy Page - wait this site is about acoustic guitars (sorry) He's no Django Reinhardt, Chet Atkins, or Michael Hedges, wait? who!? He's no Robert Johnson, Eric Clapton or Ben Harper - more familiar? Anyway you get the point :-)

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