Truss Rod and Bridge Adjustment for Perfect Guitar Intonation
In the original version of the course I explained, “Changing strings isn’t like changing the oil in your car, it won’t make your guitar last longer. You won’t damage your guitar by not changing strings.” Still, there are advantages to new strings – they’re brighter sounding and can help a guitar sound in tune with less dissonance. An example of dissonance is when a chord is played with some notes slightly out of tune.
Get in Tune – How to intonate your guitar
A beginner guitarist isn’t overly concerned with dissonance because they’re usually grabbing strings in a manner that pulls them slightly sharp or flat. Even a simple chord played on a perfectly tuned guitar sounds out of tune. As musical skills mature the attention to pitch evolves - musicians become more aware of pitch and dissonance.
Have you ever noticed that some chords and notes sound out of tune on your guitar while others sound perfect? For example the open A minor chord might sound in perfect tune but the D barre chord at the fifth fret may sound dissonant. You can actually tune the individual strings to make the D barre chord sound perfect and other chords will sound dissonant. This is caused by notes at the twelfth fret and beyond being out of tune when the open strings are tuned to pitch. What’s happening is, high frequency overtones aren’t in tune and these overtones sound even when playing open chords. The cure – adjust your guitar so the open strings and notes at the twelfth fret are all tuned to pitch. This is accomplished by adjusting the intonation.
When the intonation is properly adjusted all notes will be in tune or at least very close. Do to the physical construction of the guitar it will never be in perfect tune but the idea is to get it as close to perfect as possible.
To tune the twelfth fret to the open strings you must slightly lengthen or shorten the string. If the twelfth fret is a little sharp, the string needs lengthened to correct the pitch. Conversely, if the note is flat, the string needs shortened. It’s safe to assume that the intonation on your guitar was set properly at the factory or by your local guitar tech. Over time the neck moves causing notes at the twelfth fret to become a little sharp or flat. Use a digital tuner to tune the open strings to pitch. Now check the tuning of notes at the twelfth fret and higher. You’ll probably notice that all are a little sharp or all are a little flat.
Here’s why. There is a constant tug of war between the strings and the truss rod, the bar that runs through the middle of the neck to protect the neck from becoming warped. The tension of the strings pull the headstock towards the bridge. This bows the neck causing a gap between the fretboard and strings. This bow actually shortens the strings causing notes high up the fretboard to sound sharp. The truss rod bends the neck in the opposite direction to counteract this pull from the strings. Tightening the truss rod effectively lengthens the strings. So when the truss rod overpowers the pull of the strings, notes at the twelfth fret become flat because the strings are lengthened.
It’s beyond the scope of these instructions to explain exactly how to adjust the intonation on your guitar but this information is easy to find on the Internet, from your guitar’s manufacturer, or from our Guitar Setup and Repair program. I’m just going to explain the basic process of intonating a guitar without explaining the mechanics of adjusting different models.
First, put new strings on your guitar before doing any intonation adjustments. Strings affect intonation in many ways. For example, if you change the gauge of strings intonation is affected. As strings age the intonation changes so it's important to make these adjustments using new strings. After making these adjustments you probably won’t need to do this again for several months if you continue to use the same gauge and brand of strings.
When you change the strings replace them one at a time. If you remove all of the strings at once it will take a few days for the neck and bridge to return to a normal position. After replacing the strings, wait a day or two before making any adjustments. It takes time for the neck and truss rod to settle down after a string change. So, two or three days after replacing the strings tune the open strings to pitch and check the tuning at the twelfth fret and beyond. You'll notice one of three things: 1) All notes will be flat. 2) All notes will be sharp. 3) All notes will be roughly in tune with some strings sharp while others are flat. For number 3, move on to bridge adjustments because your truss rod is adjusted properly.
If the twelfth fret is sharp tighten the truss rod a quarter turn, retune the open strings and check the twelfth fret tuning. If it’s still off, wait until tomorrow to readjust another quarter turn. Quite often the truss rod is stuck but will snap into place over time. Conversely, if notes at the twelfth fret are flat loosen the truss rod a quarter turn. It may take a day or two but you should be able to get the twelfth fret adjusted properly IF the truss rod is functioning. The reason for the big IF is, sometimes the truss rod can be completely loosened and the neck is so bowed (converse bow) that the strings can’t pull the neck into proper position. This often occurs with vintage instruments.
When the intonation is adjusted properly the neck will be slightly curved to allow space between the frets and the strings. If the neck was adjusted perfectly flat strings would rattle against the frets.
||The black plastic triangle covers the truss rod.
||The red arrow is pointing at the truss rod adjustment nut.
||This is the tool that is used to adjust the truss rod.
||The six screws at the top of this photo are used to adjust the Floyd Rose bridge pieces. Notice the symmetry of the six pieces. The three wound strings are adjusted with the low E string piece the farthest back, next the A string and the D string is the most forward. The unwound strings have a similar symmetry with the high E string the most forward (toward the top of photo)..
When the truss rod is adjusted properly you’ll probably still notice that the intonation needs some fine tuning - some strings are flat while others are sharp. Over time maybe the neck twisted a bit or the string gauge changed. Fine tuning is performed at the bridge. The tiny bridge pieces that touch each string are moved toward the headstock to shorten the string (sharpen notes at the 12th fret) or moved in the opposite direction to flatten the note. Les Paul tune-o-matic type of bridges are simple to adjust. If you’re unfortunate (like me) to use a Floyd Rose bridge my heart goes out to you. You’ve got to loosen each string, make the adjustment, retune, check the tuning, if it’s off loosen the string, make the adjustment, retune….. hate life, spend the next hour cursing….. Anyway, it’s not fun but can be accomplished with a little patience.
A closing thought. Intonation, as mentioned before, will never be perfect. If your frets are worn, notes played on those frets will be out of tune. Sometimes frets pop up a bit throwing notes out of pitch at those frets. If you’re noticing notes out of tune throughout the neck it might be time to either have the frets dressed (leveled) or after excessive use, replaced. Tracy Longo does an excellent job explaining these adjustments and more in his Guitar Setup and Repair DVD / Digital Download. He covers adjustments for the most common types of guitars and bridges including Strats, Gibson’s, and Floyd Rose.
Doug Marks, Metal Method Instructor and author of The Complete Basic Course and Classic Guitar Licks