Truss rod

Truss rod

A truss rod is a guitar part used to stabilize and adjust the lengthwise forward curvature (also called "relief"), of the neck. Usually it is a steel rod that runs inside the neck and has a bolt that can be used to adjust its tension. The first truss rod patent was applied for by Thaddeus McHugh, an employee of the Gibson company, in 1921 [US patent reference
number = 1446758
title = Neck for musical instruments
inventor = Thaddeus McHugh
y = 1923
m = 02
d = 27
— first patent known on truss rod.
] , although the idea of "truss rod" can be encountered in patents as early as 1908 [US patent reference
number = 964660
title = Stringed musical instrument
inventor = George D. Laurian
y = 1910
m = 07
d = 19
— a patent on instrument that is "designed like harp guitar", but it mentions "truss rod" concept "to prevent a head springing under the strain of strings".
] .


When the truss rod is loosened (i.e. moved towards the guitar's body), it allows the neck to bend slightly in response to the tension of the strings. Similarly, when tightened (i.e. moved towards the guitar's headstock) the truss rod straightens the neck by resisting the tension of the strings.

It is desireable for a guitar neck to have a slight relief in order that reasonably low action is achieved in the high fretboard positions, while at the same time, the strings ring clearly in the low positions. Improved action in the high fret positions also allows for more accurate intonation, to be achieved with less compensation at the bridge.

Truss rods are required for instruments with steel (high tension) strings. Without a truss rod, the guitar's wooden neck would gradually warp (i.e. bend) beyond repair due to applied high tension. Such devices are not normally needed on instruments with lower tension strings, such as the classical guitar which uses nylon (previously catgut) strings.

Construction and action

Truss rods are frequently made out of steel, though graphite and other materials are sometimes used.

The truss rod can be adjusted to compensate for expansion or contraction in the neck wood due to changes in humidity or temperature, or to compensate for changes in the tension of the strings (the thicker the guitar string, the higher its tension when tuned to correct pitch).

Usually, the truss rod of a brand-new instrument is adjusted by the manufacturer before sale. Adjusting the truss rod is not recommended for a novice, as guitar necks can be easily damaged beyond repair in the process. Luthiers or more experienced players can adjust it when necessary (e.g. if strings of a very different tension are to be used). Turning the truss rod clockwise will tighten it, counteracting the tension of the strings and straightening the neck or creating a backward bow. Turning the truss rod counter-clockwise will loosen it, allowing string tension to act on the neck and creating a forward bow (higher string action).

Some guitars (notably Rickenbackers) come with dual truss rods that are more stable and not affected by seasonal climate changes, they are also more difficult to adjust and should be serviced by a professional. Though uncommon there are also left-handed truss rods that need to be rotated in the opposite direction of a normal truss rod.

Location and adjustment

The truss rod tension is usually controlled using an adjustment bolt (a hex nut or allen-key). Depending on the model of guitar, this bolt can be located:

* On older Fender-style electric guitars with bolt-on necks (and vintage re-issues) — on the heel of the neck. Adjustment of such truss rods can be done by a Phillips screwdriver and requires prior removal of the guitar's pickguard or neck.

* On newer Fender-style electric guitars — behind the nut, uncovered and can usually be adjusted by a 1/8" (3 mm) Allen wrench.

* On set-neck electrics — under a cover-plate behind the nut. Gibson & Epiphone guitars have their truss rod bolt covered with a signature bell-shaped plate. Most Gibson electrics have a 5/16” (8 mm) or a 1/4" (6 mm) hex adjustable truss rod nut that can be adjusted with a hex box spanner wrench.

* On acoustic guitars — inside the guitar body, accessible through the sound hole, or on the headstock. Martins use a 3/16" (5 mm) Allen wrench and Gibson uses the same as for the Gibson electrics above.

* Counterclockwise adjustment will decrease the truss rod tension (correct an overbow) and clockwise adjustment will increase the truss rod tension (correct an underbow).

Installing a truss rod in a newly constructed guitar requires woodworking capabilities. Special tools are required including a router with a variety of bits and ability to work with metals. Completed truss rods can be purchased through suppliers or manufactured according to specifications given in literature. Be sure of your measurements when constructing a guitar as they all play into the guitars full scale and playability. Consult a professional luthier or literature before constructing your own guitar.

Dual-Action Truss Rod

A dual action truss rod can be adjusted for both upbow and backbow. The original design truss rod does not compensate for a lack of relief or backbow because in most cases guitars do not suffer from a lack of relief. It is important to note that dual action truss rods adjust the opposite way to a standard truss rod to compensate for too much neck relief.

See also

*List of guitar-related topics


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Look at other dictionaries:

  • Truss rod — Truss Truss, n. [OE. trusse, F. trousse, OF. also tourse; perhaps fr. L. tryrsus stalk, stem. Cf. {Thyrsus}, {Torso}, {Trousers}, {Trousseau}.] 1. A bundle; a package; as, a truss of grass. Fabyan. [1913 Webster] Bearing a truss of trifles at his …   The Collaborative International Dictionary of English

  • Truss rod — Schematischer Schnitt durch den Hals einer E Gitarre Der Halsspannstab (engl. truss rod) ist eine Vorrichtung zur Stabilisierung und Justierung eines Gitarrenhalses. Da bei Darm oder Nylonsaiten keine übermäßig hohen Spannungen auf den Hals… …   Deutsch Wikipedia

  • Truss rod — Barre de réglage La barre de réglage [1] (ou truss rod en anglais) est une tige métallique présente à l intérieur du manche des guitares et des instruments avec des cordes sous forte tension. Cette pièce sert à stabiliser la forme du manche… …   Wikipédia en Français

  • truss rod — noun 1. : a tensioned rod for trussing a wooden beam 2. : a diagonal tie rod in a truss * * * Building Trades. 1. a tie rod in a truss. 2. a diagonal iron or steel reinforcement in a wooden beam. 3. any iron or steel rod serving as a tension… …   Useful english dictionary

  • truss rod — Building Trades. 1. a tie rod in a truss. 2. a diagonal iron or steel reinforcement in a wooden beam. 3. any iron or steel rod serving as a tension member. [1870 75] * * * …   Universalium

  • Truss — Truss, n. [OE. trusse, F. trousse, OF. also tourse; perhaps fr. L. tryrsus stalk, stem. Cf. {Thyrsus}, {Torso}, {Trousers}, {Trousseau}.] 1. A bundle; a package; as, a truss of grass. Fabyan. [1913 Webster] Bearing a truss of trifles at his back …   The Collaborative International Dictionary of English

  • Truss (disambiguation) — Truss may refer to:*Truss, a static structure consisting of straight slender members inter connected at joints into triangular units **Box truss, a structure composed of three or more chords connected by transverse and/or diagonal structural… …   Wikipedia

  • Truss — For other uses, see Truss (disambiguation). In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes.… …   Wikipedia

  • truss beam — noun : a beam reinforced by a truss rod or formed of straight or cambered pieces joined by trussing * * * truss beam noun 1. A wooden beam strengthened by a steel tie rod 2. A steel framework acting as a beam • • • Main Entry: ↑truss …   Useful english dictionary

  • Side rod — Side Side, a. 1. Of or pertaining to a side, or the sides; being on the side, or toward the side; lateral. [1913 Webster] One mighty squadron with a side wind sped. Dryden. [1913 Webster] 2. Hence, indirect; oblique; collateral; incidental; as, a …   The Collaborative International Dictionary of English

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