How to Adjust the Tension Rod on an Acoustic Guitar
When the neck on your acoustic guitar is not as straight as is should be, it is time to adjust the tension, or truss, rod. The tension rod runs the length of the guitar's neck and can be adjusted to correct either bow or warp. Bow is when the neck is bowed back, and warp is when the neck turns up. You can make the necessary adjustments at the guitar's headstock, right behind the nut where the fingerboard begins. Be cautious, as a wrong move can crack the neck.
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Things You'll Need
- Guitar truss rod wrenches, or Allen wrench set
- Quarter-inch socket set
- Long socket set
- Small Phillips screwdriver
- Red magic marker
Instructions
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1
Determine the adjustment necessary. Hold the bottom, or low "E" string, at the first fret and 14th fret at the same time. While holding the string down, look at the string gap, if any, at the sixth fret. If there is no gap, the neck is either straight or back-bowed. The presence of a considerable gap indicates a warped neck, or upwards-bent neck. To confirm back-bow, buzzing will likely occur when playing at the lower frets. You need to loosen back-bowed necks and tighten warped necks.
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2
Remove the cover on the guitar's headstock using a small Phillips-head screwdriver. Inside will either be a nut on a threaded rod, or an Allen wrench head. The nut and rod set up is typically found on older guitars, while Allen heads are found on newer and foreign-made acoustics. There is not a standard size for these fittings, so an assortment of different size Allen wrenches is recommended. They can be either metric or standard, depending on the country of origin.
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3
Mark the top center of the adjusting nut with a magic marker. This helps locate the position you started for future reference. Place the adjusting tool or Allen wrench into the truss rod adjusting nut, ensuring there is a good fit. An ill-fitting wrench can strip the adjusting nut. If possible, use the tension-rod adjusting tool.
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4
Turn the truss rod counter clockwise to loosen it. In order to free the rod, loosen the tension rod first. If the neck is back bowed, loosening is the required adjustment.
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5
Tighten the truss rod slowly. If there is any resistance, stop immediately. Tightening is the adjustment necessary for warped necks. Turn the fitting a quarter turn past the marked starting point.
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6
Check the neck for straightness. Repeat the process from step one to confirm the adjustment made. If more adjusting is needed, repeat steps three through five. When finished, replace the truss rod cover and tune the guitar.
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Tips & Warnings
In most cases, turning the adjustment fitting a quarter turn in either direction is all that is required.
Another method to check the straightness of the neck is to look down the neck at eye level. While holding the guitar body close to your eyes, point the guitar down and look down the fret board. You can easily see bends from this position.
Do not make this adjustment simply to lower the action on your acoustic guitar.
The neck straightening process is an adjust and check process. A slight turn of the tension rod requires checking the neck and strings after.
References
Resources
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