How To Adjust A Guitar’s Truss Rod?

Your guitar’s truss rod is one of the most important elements in keeping your guitar feeling good! It can also be scary to adjust for the first time if you do not know how. Even so with the correct knowledge and very basic tools you will find it a simple job that will have a big affect on your guitar’s playability.

So let me help you with all the tips you need to feel confident and keep your guitar feeling at its best.

What does the Truss Rod do?

The truss rod is a metal rod that runs through the entire length of the guitar’s neck. Because the strings are on the front of the neck, their tension bends it forwards. The truss rod counteracts this by pulling in the opposite direction.

How does it do this? There are a few different designs of truss rod. Some are dual action meaning they can be adjusted both ways bending the neck either forwards or backwards. Other single action ones only oppose the strings. They all however work on a similar concept, a metal bar with a threaded end that can be tightened. This contraction pulls against the tension of the string. Most guitars now days have a dual action truss rod. They have two parallel rods/bars and only one is adjustable. In the neutral position they are both the same length and the rod remains straight. If the adjustable rod is tightened to make it shorter than the other it will bend towards the shorter bar. This would bend the neck backwards. The opposite can be done to bend the truss rod and neck in the other direction.

What are the symptoms of an incorrectly adjusted Truss Rod?

A truss rod that has not been well adjusted can either cause fret buzz or an action*that is too high.

Often these results of a badly adjusted truss rod are mistakingly thought to be an issue in bridge height. The bridge is often raised in order to correct string buzz or lowered to get a lower action. However, in doing this you will find the height of action needed in order to eliminate string buzz is far greater than with a correctly adjusted truss rod.

How do you check the neck to see if it needs adjusting?

The first step before making changes is to check if the truss rod needs to be adjusted. And if so in which direction? To check this we have a simple process.

1. Hold down both fret one and fourteen (tip: a capo on fret one frees up a hand making this easier)
2. Check the height of the string at fret six

As the string is under tension it creates a straight line that we can use to see if the neck has any bend in it. Also by tapping the string at the sixth fret you can feel how high it is off the fret if at all.

What is the perfect Truss Rod adjustment?

Surprisingly you do not want your guitar’s neck to be totally straight. Ideally you want the neck to bend very slightly forward (around half a millimetre at the sixth fret). This is because as the string vibrates it makes an elliptical shape. A neck with this slight bend forward (known as relief) will compliment the elliptical vibration of the strings. This will allow you to have a generally lower action before experiencing fret buzz making your guitar easier to play and more enjoyable.

If you use softer strings they will have a greater movement and a little more relief may be needed. Higher gauge strings can have less relief for the same reason.

Now that you have been able to clearly see the neck’s relief you can decide what your guitar needs.

Do you tighten or loosen the Truss Rod?

Too Tight

If the truss rod is too tight it is pulling more than the strings and will then bend the neck backwards. Too tight will result in fret buzz.

Too Loose

If the truss rod is too loose the pull of the strings will bend the neck forwards adding relief. Too loose will again give you a high action which making your guitar harder to play.

How do you adjust the Truss Rod?

You’ve done your checks and now it’s time to level-up your guitar. Most truss rods only need an Allen Key in order to adjust them. Some guitars use a small bolt instead. This can either be found at the heel of the neck on the bridge end or under a small plate just above the top nut. With either one of these the adjustment is the same.

Usually the guitar will come with the correct sized tool. If not the only issue you may come across is the difference between metric and imperial sized tools. As the metric and imperial sizes do not totally line up you may for instance find that your 4mm Allen Key is too small whereas your 5mm is slightly too big. In this case you may find it need the Imperial size of 3/16″ for a perfect fit.

If there is too much relief, then tighten slightly. If there is not enough, loosen. Be very careful not to over do it!! An 1/8^th or 1/4^th turn is usually enough. Once you have made this adjustment you will want to leave your guitar for a few hours before doing more. It can take the wood time to move into place and settle. So be very careful and take your time rather than over adjust and damage your guitar.

Finally never leave the truss rod in a totally neutral position with no tension. This can create vibrations in the rod that are just annoying to hear and feel when playing. tighten it up to the point of enough tension for no unwanted vibrations while not moving the neck out of position.

When do you need to adjust the Truss Rod?

When you change strings the different tension in the new strings can require slight adjustments in the truss rod. Also throughout the year the humidity changes and this has a noticeable affect of the wood of your guitar. So a good rule of thumb is when you change strings (a day after so it can settle) or if you move your guitar to a different environment along with a few times a year with the seasons. It only takes about ten seconds to check so no excuses!

Always remember, a guitar that is kept well adjusted will stay sounding at its best and will be far easier to play. So check out my other maintenance tips and tricks and as usual ask any questions you have.

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