Your guitar’s truss rod is a bit of a hidden hero. It reinforces your instrument’s neck and takes on a whole lot of pressure from your guitar strings. If you notice your guitar neck is out of alignment, it could be time for a truss rod adjustment. However, while adjusting a truss rod can be a straightforward job once you get the hang of it, it’s not uncommon to overdo it and end up with more issues.
In my time as a guitar technician, I’d like to think I’ve mastered how to adjust a truss rod quickly and effectively to correct everything from back bow to fret buzz. Here are my tips to adjust your guitar’s truss rod and get your instrument in perfect alignment.
Why might a truss rod need adjusting?
A truss rod is a metal or graphite rod embedded in a guitar's neck that allows you to adjust the neck's curvature so you can achieve the best playability and string action.
Truss rods can need adjusting for a range of reasons, and you may find that issues you thought were unrelated all stem from a misaligned truss rod. However, the most common reason is to adjust the relief in the neck.
Neck relief
Have you noticed your guitar neck has some inconsistencies when playing? Is there a lot of fret buzz in one section but not in others? If the neck starts to bow forward or backward, it can affect your instrument’s playability, and that’s a sign the truss rod may need adjusting.
A properly adjusted truss rod should have a very slight forward bow where the fretboard isn't perfectly straight but gently bows outward. Think of it like a subtle ‘U’ shape if you were to look at your guitar side-on while it’s laid on its back.
This creates a small gap between the strings and the middle frets, so you can play with minimal string buzz. This gap should be around 0.010” — enough to slide a business card through. If the gap is bigger, it suggests the truss rod is too loose and there is excess relief in the neck. The guitar will bow forward, raising your string action. In this case, the strings will buzz against the frets higher up on the fretboard, usually from the 15th fret upward.
On the other hand, if the guitar bows backwards, reducing the neck relief gap (in some cases, none at all), it can lower the string action too much, creating fret buzz around the middle of the fretboard, from the 5th to 9th frets approximately.
Humidity changes
As well as things like string tension, changes in the weather can also cause a change in the relief of the guitar neck. High humidity levels can cause the wood to expand, while dry conditions cause it to contract — both can affect your guitar’s intonation and string action. Variations in humidity can particularly affect acoustic guitars.
Truss rod adjustment can help compensate for these environmental changes.
Changing string gauge
Have you recently switched to a heavier or lighter string gauge? Doing so can affect how much tension your guitar’s neck has to cope with.
Heavier strings exert more pull which can potentially cause the neck to bow forward. Lighter strings, on the other hand, need less tension to reach their desired pitch, and that means the neck can back bow, especially if changes from a heavier gauge to lighter gauge string set. By adjusting the truss rod, you can help balance this tension.
How to adjust a guitar truss rod
You might be wondering if you can adjust your guitar’s truss rod yourself. You can indeed — and I’ll outline the basic steps in a moment. However, like any guitar repair, if you don’t feel confident in going the DIY route, always get help from a guitar technician. Incorrect repair techniques can lead to more issues, costing time and money.
So, where to start with adjusting a truss rod? Firstly, it’s important to note that there are several types of truss rods, but most modern guitars will have either a single-action or dual-action (two-way) truss rod.
While a single-action truss rod can add tension, it can’t do what a two-way truss rod can when it comes to adding relief, so keep in mind when we talk about adding relief, this is only applicable to a two-way truss rod system.
Luckily, this is what most modern guitars have! If in doubt, research your instrument and its hardware through the serial number, or contact a local guitar technician for advice if you can’t find one.
1. Find the tools you need
The tools needed for adjusting your truss rod depend on the type of guitar nut you have. The adjusting tool should come with your guitar (if you have a second-hand guitar, you should be able to look the model up), and it will be one of the following:
Allen key (Most Fender models use a ⅛” imperial Allen key. Ibanez, ESP, and other brands use a 4mm metric key).
Specialist adjusting wrench (most Gibsons and PRS use these. Sizes vary, so have a look at your guitar specs to find out the appropriate size).
Phillips head screwdriver (commonly found on vintage Fenders and other manufacturers such as Tokai). These nuts are situated at the base of the neck, and you may sometimes need to take the neck off to adjust the truss rod.
Spoke wheel guitar nuts are the most versatile in this instance, as you should be able to use an array of tools.
2. Test the neck relief
Before you make any adjustments, you need to work out your guitar’s current relief so you can work out which way to adjust the truss rod. There are two ways to check your guitar neck relief — using a straight edge or using strings.
Whichever method you use, start by tuning your guitar to pitch.
The straight-edge method
If you have a straight edge or notched straight edge to hand, lay it along the fretboard, spanning from the first to the last fret. If you’re using a notched straight edge, align it so it rests directly on the fretboard wood, avoiding the frets.
Now check the gap between the straight edge and the frets around the 7th to 9th frets.
A small, consistent gap (so you can slide a business card through) indicates proper relief. If there’s too much gap, the neck has an excessive forward bow, and you’ll need to reduce it by adjusting the truss rod. If there’s little to no gap, the neck might be too straight or back bowed, so it’s time to add more relief.
The string method
This measures the relief between the first fret and where the guitar neck meets the body (usually the 15th fret).
If you have a capo, place this on the first fret.
Fret the 15th fret on the low E string using your right hand.
With your left hand, tap the top of the low E string against the top of the 8th fret. (You can reverse your hand placements if you’re left-handed).
This is your relief measurement. As mentioned earlier, you should be able to slide a business card through (again, this works out as 0.010”).
If there’s no gap, you need more relief. If there’s a lot of relief, you need to increase the truss rod tension, lessening the neck relief.
3. Adjusting the truss rod
Now you know whether you need to add or reduce relief, you can adjust the truss rod.
Using your Allen key, wrench, or other appropriate tool, apply it to the nut and turn — the universal ‘righty tighty, lefty loosey’ rule applies here. Clockwise will tighten your truss rod, reducing relief, while counterclockwise will loosen the tension, adding relief.
Please note: It’s really important to work incrementally here. As a general rule of thumb, never adjust more than a quarter-turn at a time. Turn, test, then turn again — you may need to do this several times to get the right relief. If you turn too much at once, it’s very possible to break your truss rod.
Potential challenges
Have you tried to adjust your truss rod and found it’s too stiff or seized? You can try adding a drop of mineral oil, letting it seep down to the threads, and leaving it for half an hour. Then, try adjusting it again.
If you still find it’s too tricky to turn, I recommend taking your instrument to a guitar technician.
Looking for a guitar technician in Cardiff?
If your guitar is in need of a truss rod adjustment, repair, or general service and you’re located near Cardiff, please feel free to get in touch. As an experienced guitar technician and luthier, I’ve adjusted many a truss rod in my time! I’m always happy to take a look and see what I can do.
Take a look at my other guitar services and contact me to chat about your instrument.
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