Why Not Adjust Action With Truss Rod?

[calstang66]

Why do most youtube videos say not to lower my guitar's action, by tightening the truss rod?
It works, it's easier to do than sanding the saddle and not as permanent as sanding the saddle.
And, I found 1 of my guitars, the truss rod was very very loose, so it actually needed tightening.
Is there a sequence of steps to take before using the truss rod, to lower the action?
If I do tighten the truss rod, should I leave full tension on the strings when I tighten the truss rod?

[mr. beaumont]

I think most people would agree that a tweak of the truss rod CAN affect string action.

The thing to keep in mind is what is actually happening when you adjust the truss rod...it's changing the geometry of the neck. Sometimes, you don't want to do thst...if the neck is already straight (or has the amount of relief that makes it feel best) you don't want to change that to adjust action.

Ignoring this is is the thing that leads a lot of people to over adjusting the truss rod...and never getting the guitar where they want it.

[mirwa]

Originally Posted by calstang66

Is there a sequence of steps to take before using the truss rod, to lower the action?
If I do tighten the truss rod, should I leave full tension on the strings when I tighten the truss rod?

Yes, do not use the truss rod to lower the action, thatis not what it is there for.

A badly adjusted truss rod can when adjusted correctly lower the string action, but it’s a side effect.

Necks are shaped for the comfort of the hand, as the shape on the back of the neck gets thinner and thinner, the remaining wood can no longer support the string tension and the neck bowsin an upwards direction ( we refer this as excessive relief) as such we insert a strengthening beam internally to the neck (truss rod), some truss rods are adjustable some act more as a strengthening beam.

Adjusting the truss rod correctly to do its job, will as a side effect lower the string height, however once the correct height is achieved the truss rod is now doing the job it was designed to do, from here you have to lower the saddle.

Steve

[fazool]

Originally Posted by calstang66

Why do most youtube videos say not to lower my guitar's action, by tightening the truss rod?...

Because the truss rod doesn't adjust action. it adjusts relief.

Originally Posted by calstang66

...It works..

As Mirwa said, when it works it's a side effect of changing the relief.

Before just rationalizing how to do something you stated you were advised against doing, study up on the adjustment and setup of a guitar.

[John Arnold]

Because the truss rod doesn't adjust action. it adjusts relief.

Actually, it does both.

Plain and simple, you only adjust the truss rod to optimise relief. Optimal relief is usually between 0.003" and 0.010". Anything outside of that will create problems. Too much relief will cause the guitar to be unnecessarily hard to play, and the tendency to buzz will be greater past the 6th fret. Too little relief or back-bow will cause the action to be low near the nut, but too high on the upper frets. It also will increase the tendency to buzz near the nut.
Correct relief is when the tendency to buzz is the same all along the neck.
Because truss rod adjustments affect action, you should always do that before setting the action at the bridge.
If you are lucky, setting the relief will give you the action you seek. But I wouldn't count on it.

[fazool]

Originally Posted by John Arnold

Actually, it does both....

only as a side effect.

Action is the height of the strings from the fretboard. The strings and fretboard are not parallel - they are at a slightly divergent angle. The strings are a straight line but the neck has a slight bow in it.

In this picture, the straight orange line represents the string. The brown uneven arc represents the fretboard (note if it was flat how it would have a divergent angle). The black triangle represents the nut and blue the saddle.

You need height at nut, height at saddle and curvature creating relief.

With those intertwined adjustments you can dial in the action, relief and change of action (diverging angle).

When you change the curvature with the truss rod it gives you relief so higher frets don't buzz. In altering the geometry of the neck you will change the action, but you will be changing other things as well.

[Mbroady]

Truss rod adjustment is part of the equation but not a solution to higher action. If the guitar has to much relief then by all means a tweak can have the consequence of lower action. And before a saddle is lowered to achieve the desired action the relief should be properly set, via the trus rod. The nut depth, or lack of, is also part of the equation, hence why a good set up that includes the Nut Depth, neck relief, and saddle hight (as well as fret hight) can make a guitar that is difficult to play a joy to play.

[N+1]

There are things here that I don't understand (and don't think I believe). There is no 'exactly perfect relief' that should be set at the outset. A suggested range of values is given by John Arnold above (O.003" to 0.010") but even those limits are not carved in stone.

Let us suppose that I'm playing my guitar and find that the action (for whatever reason) is a little higher than I like (temperature and humidity may have changed, or just time has had an effect, or maybe I've changed my strings). Suppose I now measure the relief and find it to be 0.010". I tweak the truss rod until it's (let's say) 0.005". I find my action has now fallen by (let's say) 0.5mm and feels comfortable again, and (I am assuming) there is no fret buzz. Everyone is happy. I'm happy. The guitar is happy. And I will tell my friends, perhaps, that I have adjusted the truss rod, within a reasonable range, to lower the action.

You could say that all I was doing was reducing the relief, and inadvertently it reduced the action. But that's just wordplay, isn't it? I remember Andy Powers talking in a Taylor video about the slight wiggle room around the nominally perfect neck angle - surely there's also slight wiggle room around the nominally perfect relief, and we can use that to advantage.

[Silly Moustache]

Using your truss rod "just" to increase/reduce the action, is like letting down your tyres to keep the speed down.
Over tightening the T/R means you'll get fret buss from 5th fret up.
Under tighterning (is that a thing?) sinply makes the action too high in the same area.

T/Rs only really act on the neck around the middle of the fretboard between the nut and the body join - any more and you're dong it wrong.

[N+1]

Originally Posted by Silly Moustache

Using your truss rod "just" to increase/reduce the action, is like letting down your tyres to keep the speed down.

I don't think the analogy works. A slight tweak of the relief (say from 0.010" to 0.006" - or name your own values) may have a significant effect on the action without causing any problems. If it does - I can see no reason for not accepting the gift and making the adjustment.

I'm not advocating using the truss rod as a large-scale action changer - just suggesting tiny tweaks of relief within the 'wiggle room' that each guitar permits.

[jonfields45]

New guitars with a Gibson/Fender/Taylor style truss rod (curved metal in a wooden channel), often develop action impacting large forward relief sitting in a shop. It is the case that some truss rod adjustments are quite important for action.

For guitars with long necks of relatively less stiff wood, an original SG comes to mind, if you set them to just the back bow side zero relief or more they can react by twisting which can become permanent. I would not risk tweaking action with zero relief on an original SG.

Once you've used the truss rod to set relief to your preference, then the rest of the way needs to be done by other means.

[ChrisN]

"Just a little more will do it, I'm almost there" and suddenly the truss rod nut has stripped its internal threads, rendering your truss rod useless. Happens every day. Try to sell your guitar with non-functioning truss rod, then price the repair.

The range of adjustment via the truss rod is inadequate and the adjustment point is incorrectly located. You're bending the neck backward from the middle, not leaning it back from the base/heel. You do lower the action a smidge with no harm done, but beyond a smidge, you're in the danger zone.

I bought a used guitar (sight unseen) that the seller had lowered the action on by cranking down the truss rod, but he way overdid it and introduced a back-bow, which made the action look OK (sort of), but added buzzing/lifting frets where they didn't exist before. Easy fix for me, and lucky break for him that he didn't strip the rod/nut.

As others said, use the truss rod for its purpose - to set relief - only. Lower the action via saddle reduction, or neck reset.

[redir]

I also do not subscribe to the idea that the truss rod doesn't adjust the action, it does. But it does so by adjusting the relief. If you have too much bow in the neck, too much relief, then use the truss rod to set the relief properly and voila! You have also lowered the action. But if your relief is set properly then it's a bad idea to lower the action using the truss rod. Because then you will flatten, or worse, but back bow in the neck. Then you will have lowered the action but now you have poor fretting.

I have had many many guitars come through my shop where customers complain of high action. I take one look at the neck and see that the relief is huge, so one or two tweaks of the truss rod and they leave a happy customer. So again, the truss rod can be used to adjust the action if and only if there is excessive relief that needs to be adjusted proper.

[N+1]

Originally Posted by redir

So again, the truss rod can be used to adjust the action if and only if there is excessive relief that needs to be adjusted proper.

Indeed. No one can argue with that. Much more succinct, and clearer, than my own posts!

[fazool]

Originally Posted by Silly Moustache

Using your truss rod "just" to increase/reduce the action, is like letting down your tyres to keep the speed down. ...

Originally Posted by N+1

I don't think the analogy works. ....

OK, so I will suggest it's like letting air out of your tyres to make your car lower to the ground.


(notice how I kept Andy's Brit spelling )