Guitar Truss Rod Adjustment Guide
Guitar Truss Rod Adjustment Guide
This article provides a top-level view of how a truss rod works and how to adjust a truss rod. Adjusting a guitar truss rod is a key part of maintaining optimal playability.
Understanding Your Truss Rod
BEFORE YOU DO ANYTHING TO YOUR TRUSS ROD you need to have a reasonably good understanding of truss rods. Don’t laugh this off. You’re dealing with an engineered system and need to understand truss rod design and how a truss rod works.
All guitar truss rods are alike only with regards to their intended function, to adjust neck relief. All truss rods are made of steel, however; the composition of the steel used is not the same. The variances in steel composition, rod diameter, and manufacturing quality result in wide differences in the strength of any truss rod.
Why does truss rod strength matter? When adjusting a truss rod, in either direction, you are changing the force applied to the rod. The types of forces that act on a truss rod are compression, tension, and torque.
Loosening a truss rod (turning counter-clockwise) adds relief to (decreases tension on) the neck which results in increased (higher) string action height. Loosening the truss rod is done to correct backbow.
Tightening a truss rod (turning clockwise) increases compression, thereby pushing the center of the neck toward the strings. The MusicPlayers.com website describes it in this manner, “This straightens an up-bowed neck, pulling the peghead away from the tension of the strings. This reduces relief, lowering the string action (height of the strings over the frets). Turn the nut clockwise to tighten the rod.”1 Tightening the truss rod is done to correct upbow.
What happens if you overtighten a truss rod? As you overtighten a truss rod you move toward applying more force than it can tolerate. This force effectively becomes torque that shears (twists off / breaks) the rod or the adjustment nut. Most broken truss rods can be repaired, however; the cost to repair a broken truss rod is often more than the value of the guitar. A possible repair option is to buy a replacement but this is not cheap and brings yet another set of issues.
How many types of guitar truss rods are there? There are many types of truss rods for acoustic and electric guitars. European luthier Marguerite Pastella, of Fret Not Guitar Repair, identified five types of truss rods commonly used in building electric and acoustic guitars.2
For this article we’re going to disucss the two most common types of truss rods used for electric guitars and bass guitars. The two common truss rods are a Single Action Truss Rod and a Dual Action Truss Rod.
Single Action Truss Rod
Single-action truss rods are the most common truss rod in commercially manufactured instruments. These rods are designed to be tightened, thereby increasing pressure on the back of the neck. This results in the neck being forced to bow backward. The purpose of this is generally to counteract the tension of the strings to straighten the neck.
Dual Action Truss Rod
A dual-action, aka double-action, truss rod enables you to make neck adjustments in both directions (up or down). Uniquely, dual-action truss rods can create relief with or without string tension. Two-way truss rods have adjustment points (nuts) at each end.
Single Action Truss Rod vs. Dual Action Truss Rod
Which Way Do You Turn a Truss Rod
Which way you turn a truss rod depends on the desired effect. Before tightening your truss rod it’s always a good idea to give it a short counter-clockwise turn to loosen it. To do a professional guitar setup or professional bass setup you want the neck to be level (flat). To compensate for undesirable curvature in the neck you can adjust your neck up or down.
Decrease Relief Tightening the truss rod by turning it clockwise influences the neck to curve upward toward the strings (convex).
Increase Relief Loosening the truss rod by turning it counter-clockwise influences the neck to pull away from the strings (concave).
Check the amount of relief throughout your adjustment process. Start with a neck relief check to get an idea of how much adjusting is required. An important thing to note is that the full effect from adjusting your truss rod is not immediate. The neck usually has a bit of a delayed response. To minimize stress on your neck, don’t turn your truss rod over a 1/4-turn in any 24-hour period. Check your relief again, and adjust as necessary.
How to check relief is very simple.
For an electric guitar, simply, fret the top string at the first and last fret. (You may want to capo the first string). At the 7th fret, measure the distance between the bottom of the string and the top of the 7th fret. This measurement is your amount of relief. In a 2019 article, the folks at Sweetwater Sound discussed the importance of being able to also sight a guitar neck before adjusting a truss rod. They specifically stated, “The first step in any setup is to take a look at the neck and see what correction we may need to make. By sighting the neck, we gain insight into how the neck is reacting to the string tension and truss rod relief. At this point, we’re just trying to get an understanding of whether the neck is straight or not.”.3
For a bass guitar, fret the top string (low E) at the first and at the 15th fret. (You may want to capo the first string). At the 7th or 8th fret, measure the distance between the bottom of the string and the top of the 7th fret. This measurement is your amount of relief. As a contributor to the Premier Guitar blog, Tony Nagy commented “More than likely you’re thinking about the setup because, in some way, your instrument is not performing the way you’d like. To pinpoint any problems, we need to look at all the factors that affect your instrument’s overall playability, sound, and function.”.4
There is no standard, single measurement that works for every guitar. As a guide you can use .008″ to .015″. The optimal amount of relief is largely a personal preference.
After you’ve done this, if you still don’t like your string action, you may need to adjust your bridge saddle heights. After making these adjustments you need to check and adjust the intonation. Because the neck responds slowly, you may find that the intonation needs to be reset after a few days.
What if my truss rod won’t turn or tighten?
Always stay on the side of caution when adjusting a truss rod. If you have any concerns about an inability to turn a truss rod it’s time to consult with a luthier or local guitar tech.
What Tools Do I Need to Adjust a Truss Rod?
A list of tools required to adjust a truss rod is relatively short. You may not need everything listed here. For example, not every guitar has a truss rod cover, so there’s no need for a screwdriver.
- Small scewdriver (if you need to remove a truss rod cover)
- Adjustment Wrench that fits your guitar’s truss rod nut
- String height gauge with 1/32″ and 1/64″ markings
- Electronic tuner (clamp on or rack mounted digital tuner)
There is not a standard type or size wrench for all guitar truss rods. Possibilities are hex wrench, box wrench, nut driver or screwdriver. Truss rod wrenches are made in metric and SAE (Imperial) sizes.
Some guitars require a more specialized tool. John LeVan, a writer, and guitar repair expert at Premier Guitar stated, ” I have at least 20 different wrenches and hex keys dedicated to adjusting guitar necks, but I still run across that one guitar that requires a tool I don’t have. There are so many different tools designed for adjusting truss rods that it’s nearly impossible to have them all.”.5
USING AN INCORRECT SIZED WRENCH CAN DAMAGE YOUR TRUSS ROD NUT. Always make certain you are using the correct wrench for your particular truss rod nut.
Should I adjust my own truss rod?
Ideally, it would be great for you to know how to perform basic maintenance and adjustments. You can watch videos and read articles but you need experience.
Getting that experience includes a level of risk about breaking your truss rod, and stripping out or breaking your truss rod barrel nut. Keep in mind that a professional guitar setup costs around $55-$90. Broken truss rod repair costs from $60-$300 and up to can’t be repaired.
Don’t be discouraged. Even the best luthiers in the world at one time didn’t know what a truss rod was, much less how to adjust one. If you are somewhat mechanically inclined you can learn how to adjust a truss rod.
Improve this article for others! Leave a comment about your experience adjusting your truss rod, and include your own tips.
- 1 Dan Erlewine, “Guitar 201: Adjusting the Truss Rod”, May 3, 2017, Available from MusicPlayers.com
- 2 Marguerite Pastella, “Types of Truss Rods”, May 3, 2011, Available from Fret Not Guitar Repair
- 3 Sweetwater Writer, “How to Setup Your Electric Guitar: Adjusting the Truss Rod”, March 22, 2019, Available from Sweetwater Sound
- 4 Tony Nagy, “DIY: How to Set Up a Bass Guitar”, December 12, 2012, Available from Premier Guitar
- 5 John LeVan, “Guitar Shop 101: Demystifying Truss-Rod Tools”, June 13, 2014, Available from Premier Guitar