Truss Rod Adjustment

[AlanSam]

What Cahill said in the other post about Pomona's advice re neck adjustment after swopping in heavier gauge strings set me thinking. I've read, and taken on board that the only good reason to adjust the truss rod is to achieve/maintain a straight neck. Not adjust the action by bowing a straight neck. Any views?

[Pura Vida]

Going up to a heavier string set adds a little tension on the neck (and conversely, going to a lighter gauge reduces tension), which can cause just a slight bow either way.  This can be adjusted with a small adjustment to the truss rod.  The nut and saddle height are still good, so nothing needs to change.  Usually, these are very small adjustments (1/4 turn or two).  This all assumes that the guitar was properly setup prior to the string change.

[AlanSam]

PV - so basically you agree that the truss rod is solely for securing a straight neck?

[Jeffacme]

Yes the truss rods primary function is to control the bow in the neck. As an excellent demonstration it’s been raining for the past nine days and while playing my 000 l heard a buzz on the middle D in DADGAD when strumming a mostly open A chord so l put it on the bench checked the relief and it was dead flat. Loosen 1/4 turn, buzz gone and relief at .009” job done. People do often try using truss rod adjustments to change action height but mostly it just creates other issues.

[Pura Vida]

Yes.  As Jeffacme says, it should be used in combination with the nut and saddle settings aligned first, not as a replacement for a proper setup.  Otherwise, you're basically twisting your neck to cover up a separate issue.  A small tweak here and there is perfectly acceptable, although once I have my guitar setup, I rarely have to adjust it.

[Jeffacme]

Agreed I bought my 000 back in January and it just had a center crack repair and a bridge reglue it’s a “98” I’ve only had to make the one adjustment since the RH here has been high 80s for the last ten days or so The only other in my stable is the Bourgeois which may need a similar adjustment soon. Acoustic guitars are still living things and need a bit of attention now and then.

[RoyBoy]

Yes, the function of the truss rod is to control the amount of relief in the neck. The sweet spot for a lot of players is about 0.005" - 0.007". Now if the neck is bowed up (or "forward") and a truss rod adjustment is done to get the neck back in line, that does end up lowering the action in the process. But action is a combination of relief, nut slot height, and saddle height. And most techs/luthiers adjust them in that order.

Loosening the truss rod can alleviate a seasonal buzz, but inducing a bit of U curve can also cause the the notes from frets 7-12 to be less clean because of it. If you never play up there, no problem. I have heard of acoustic guitarists living in greater winter/summer climate changes using two different saddles, one for winter and one for summer. That actually keeps the action and response more consistent than adjusting the truss rod twice a year. Wood moves and drastic humidity changes can be catastrophic for a wood instrument

[Jeffacme]

I should that if you use alternate tunings often you are changing the neck tension particularly lowered tunings such as DADGAD the relief will change a bit which is one of the reasons I like .009-.012 neck relief since I play fingerstyle with percussive strumming I need a little more space to kill the buzz.