You don’t have to take off the strings to adjust your truss rod. In fact, you need them on and tuned to the correct pitch to make sure you get the relief correct. If you adjust a truss rod without the strings on, your adjustment will be off when you put the strings back on. [3] X Research source Your strings exert pressure on the neck of your guitar that will gradually cause it to bow more. Even if your neck relief was good for you when you first bought your guitar, it can change over time.
Don’t worry if you haven’t done this before and you don’t know exactly what you’re looking for. Sighting the neck simply gives you a general idea of the condition of the neck of your guitar and its overall straightness.
If you have a shorter scale guitar, you might not be able to get a capo on the 15th fret. Place your second capo on the fret closest to the body of the guitar where you can fit a capo. If you don’t have 2 capos, you can also fret the low E string at the 1st and 15th frets to get the same result. However, you’ll likely need another set of hands to take the measurement. [6] X Research source
If the feeler gauge encounters resistance or won’t fit at all between the string and the top of the fret, you likely need to increase your neck relief. On the other hand, if there’s still space between the string and the top of the fret after you insert the feeler gauge, you need to decrease your relief.
With some acoustic guitars, you can only adjust the truss rod through the soundhole. If you don’t see a cover or a notch for the truss rod in the headstock, look through the soundhole towards the neck to spot the truss rod. [9] X Research source
Truss rod keys aren’t standard. If you have a key for the truss rod of another guitar, it might not fit — even if the guitars come from the same manufacturer. Make sure the tool you’re using fits snugly and doesn’t slip. Otherwise, you could strip your truss rod.
It can be hard to guess how much of a turn you’re giving the truss rod if you don’t have a lot of experience making these kinds of minute adjustments. It might be easier for you to think of 1/8 as half of a quarter turn.
If you find that you’ve gone too far, you’ll have to adjust the truss rod back in the other direction. It’s also worth taking a little time to play your guitar and see how it feels. Neck relief is a personal thing. If it feels right for you to play, you may not need to make any further adjustments, even if the measurement isn’t exactly what you thought you wanted. It’s completely up to you.
Go slow and don’t force it — you could damage your guitar. A tiny adjustment is all it takes. These adjustments can take some time to get right, so don’t beat yourself up if you didn’t get it right on the first try — especially if you’ve never adjusted a truss rod before.
Avoid moving your guitar during this period. Changes in temperature and humidity can impact the truss rod adjustment you’ve made.
