How to Make a Bass Truss Rod Adjustment
It may be necessary to adjust the truss rod on your bass if the strings buzz when lower frets are played or if the action is too high in the middle of the neck. The truss rod runs up the length of the neck of the bass guitar and controls the neck "relief." Neck relief refers to the amount of curvature in the instrument's neck. There should always be a small amount of relief to ensure that the strings don't come into contact with the frets when plucked. Adjust the truss rod using an Allen key.
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Things You'll Need
- Allen key (usually provided with bass guitar)
- Capo
- Feeler gauges
- Radius gauge (see Resources)
Instructions
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Place a capo on the first fret of the instrument. Press down the G string of the instrument at the highest fret. Use the feeler gauges to determine the distance between the top of the fret marker that separates the seventh and eighth frets and the bottom of the string. Repeat this process for the E string.
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2
Check your bass guitar's neck radius using a radius gauge. Print off the radius gauge from Tune My Bass and find which side matches the curve at the back of your neck. The measurement written on the edge that fits your neck is the radius. If your bass has a 7.25-inch radius, the gap between the fret and the string should have been 0.012 inches. Radiuses between 9.5 and 12 inches should have a 0.010 inch gap. Basses with larger radiuses, between 15 and 17 inches, should have a gap of 0.008 inches between the string and fret marker. If your feeler gauge measurement was larger than this, your neck needs to be straightened, and if it was smaller, your neck needs to be bent.
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3
Locate the truss rod nut on your bass guitar by looking down at the neck from the headstock. There should be a hexagonal nut where the neck is connected to the headstock. If not, check where the neck meets the body of the guitar. This is the truss rod nut.
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Mark a small point at the 12 o'clock position on the truss rod nut. This helps you keep track of how much you've adjusted it. Insert your Allen key into the truss rod nut. Loosen the truss rod by turning the key slightly counter-clockwise before starting your adjustment. Turn the truss rod nut a quarter turn counter-clockwise if the gap between the string and the fret was too small. Turn the truss rod nut clockwise a quarter turn if the gap was too large.
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Examine the measurement again. If the strings are still too low or high, you must wait a day before attempting the adjustment again. Let the wood settle before adjusting it any further and only perform a quarter to half-turn per day.
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References
Resources
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