trussrod advice

[alyctes]

Hi folks

I have an Ibanez GSRM-20 I bought new about 10 years ago and have barely used.  I decided to sell it, went to have a look at the action. 

The action is quite high, but when I try to tighten the TR the nut gets easier to turn, not more difficult as I'd expect.  If I turn it the other way it turns normally, the action goes up. 

Does this make any sense to anyone?  I'm beginning to suspect it may be faulty.

Any advice gratefully received!

Edited November 29, 2020 by alyctes

[Chiliwailer]

Could be two way truss, what happens if you keep tightening - or at least going in that direction?! 

[alyctes]

9 hours ago, Chiliwailer said:

Could be two way truss, what happens if you keep tightening - or at least going in that direction?! 

I've not yet dared to do so; it doesn't make sense to me.  Thanks for the hint about two-way TR, though; I'll do some more reading.

[Baloney Balderdash]

The trussrod really shouldn't offer much resistance either way except for at it's maximum travel length, also you don't adjust the action with the trussrod, you do that by adjusting the height of the saddles, down by the bridge, the trussrod is used to adjust neck relief, as in how much the neck bends (usually you would want it to bend just ever so slightly forward to give the strings more space to vibrate).

And the trussrod in an Ibanez GSRM20 have a 1 way trussrod to clear that out for you as well.

Edited December 5, 2020 by Baloney Balderdash

[alyctes]

It's not the resistance that worries me, it's the lack of it.

Agree, I'm adjusting the relief.

Thanks for the trussrod note.

[Andyjr1515]

Hi

There's a bit of confusion of terminologies and assumptions here so, just so we're starting in the same place:

- Relief is about the straightness of the neck

- Action is about the height of the strings above the neck

- The relief can affect the action, but it must never be used as the primary way of adjusting the action.  You set the neck relief so that the neck is relatively straight under string tension and then adjust the saddle heights to get the action height you want.

- Ibanez basses can be fitted with single-action or dual action trussrods

- You do indeed feel a resistance to the trussrod nut turning as it starts bending the neck

- Generally when folks refer to loosening and tightening the trussrod nut, they are referring to the 'Lefty Loosey (anticlockwise looking at the nut); Righty Tighty (clockwise looking at the nut)' direction, and not necessarily the actual feel.

- Easiest way of checking the relief is: With the strings tuned to pitch, hold down at the 1st fret and 17th fret; tap down the string at the mid point 8th fret.  There should be just perceptible movement.  A gap (relief) more than a business card means the neck bow from the string tension is too great and the neck needs straightening (slacken the strings, turn trussrod nut 1/4 turn clockwise, retune, check and repeat if necessary).  If, however, there is no gap and the string at the 8th is hard against the fret, then the neck is 'back bowed' (slacken the strings, turn trussrod nut  1/4 turn anti-clockwise, retune, check and repeat if necessary)

 

So, @alyctes from what I understand - the relief, measured as above, is too great and you have been turning the nut clockwise and you have reached a point where the nut seems surprisingly easy to turn?

 

I agree with @Chiliwailer    It tells me that you have a two-way truss rod fitted and, as he says, you should keep turning (possibibly up to a full turn) and then you should start feeling the tension start building on the nut, but in the opposite direction.

Basically, a two-way trussrod sits loose in a narrow slot, held in place by the neck wood at the bottom of the slot and by the fretboard at the top of the slot.  And, depending which way you turn the knob, the rod will bend either way.  So if has been tightened the 'wrong' way - where the truss rod is actually increasing the relief and not reducing it - and you now turn it clockwise to correct that then you will reach a point where the rod is straight.  At this point it isn't trying to bend the neck at all and so the nut feels very loose.  As you keep turning it, then the rod now starts bending the opposite 'correct' way, trying to bend the neck into a backbow to counteract the bow effect of the string tension.  And because the rod is now bending the neck again, albeit in the opposite direction, the tension on the nut increases too.

So once you are bending the neck the 'correct' way, follow the above tips and you should be able to safely achieve the 'just perceptible' relief gap and then be able to adjust your action.  And the golden rule - just like you have done with this post - if you're not sure and it doesn't seem to be doing what you expect, stop and ask again here  

 

 

 

 

[alyctes]

2 hours ago, Andyjr1515 said:

So, @alyctes from what I understand - the relief, measured as above, is too great and you have been turning the nut clockwise and you have reached a point where the nut seems surprisingly easy to turn?

 

 

Thanks for this.  I agree, the relief is too high.  The neck is visibly bowed forward.  There is some adjustment possible at the bridge saddles but there seems little point until the bow is reduced - I can see it's going to be too large for saddle adjustment to work.  (I suspect the neck may also need a shim but that comes later.)

I was not certain which way to turn the trussrod to achieve a particular effect (I know that some work in the opposite direction to the 'conventional' way).  Therefore, I cautiously turned it anticlockwise (looking along the neck from the nut).  That increased the bow.  The TR was reasonably easy to turn, similar to those on other basses I've adjusted the TR on successfully.

So, I turned it in the opposite direction.  The bow reduced. 

This turn, reducing the bow, corresponded with the increasingly easy turn of the TR. 

That doesn't make sense in terms of the physics, to me; the TR should be working against the pull of the strings, so that should take more effort than turning in the other direction. That was what made me nervous.

I'll give it another quarter turn and see what happens. 

Thanks again.

[Andyjr1515]

1 hour ago, alyctes said:

Thanks for this.  I agree, the relief is too high.  The neck is visibly bowed forward.  There is some adjustment possible at the bridge saddles but there seems little point until the bow is reduced - I can see it's going to be too large for saddle adjustment to work.  (I suspect the neck may also need a shim but that comes later.)

I was not certain which way to turn the trussrod to achieve a particular effect (I know that some work in the opposite direction to the 'conventional' way).  Therefore, I cautiously turned it anticlockwise (looking along the neck from the nut).  That increased the bow.  The TR was reasonably easy to turn, similar to those on other basses I've adjusted the TR on successfully.

So, I turned it in the opposite direction.  The bow reduced. 

This turn, reducing the bow, corresponded with the increasingly easy turn of the TR. 

That doesn't make sense in terms of the physics, to me; the TR should be working against the pull of the strings, so that should take more effort than turning in the other direction. That was what made me nervous.

I'll give it another quarter turn and see what happens. 

Thanks again.

The truss rod has been actively bending the neck the wrong way ('wrong' being that it has been bending it the same way as the strings bend it, adding to the curve rather than counteracting it).  So yes, as you loosened it, then the relief has reduced as the neck started straightening. 

So if, under full string tension, the relief is now at the 'business card or less' range, you wouldn't necessarily need to turn it anymore - except to carry on turning clockwise until you start to feel the resistance.  This wouldn't bend the neck anymore but would tense the rod inside the slot and stop it rattling around (remember that the rod is, essentially loose inside there when it is fully straight).

But if the relief is still too much, then carry on turning and the rod will then start bending the neck the other way, creating the slight back-bow that will counteract the forward bow effect of the strings.

And yes you are right - there is no point in adjusting the saddles until the relief is correct.

Edited December 6, 2020 by Andyjr1515

[Andyjr1515]

I don't know if this helps.

Bear in mind that the neck has no option but to follow the same shape as the truss rod.

It sounds like your trussrod started like this.  This is with the nut turned anticlockwise:

 

Now, turning the nut clockwise until it feels loose, it's like this:

And if you keep turning clockwise, you will feed the nut tighten again and it will start to bend the other way:

 

[alyctes]

I follow.  Thank you.

[alyctes]

Finally screwed my courage up got round to turning the TR again.

The relief is reducing and the TR feels normal, after its being loose in the neck.  That felt quite odd, no resistance at all.  I'm convinced it's working correctly and will get to where I want it (quickly, because the GSRM is so short and slim).

I'm a happy bunny.  My thanks to everyone who contributed

 

Edited December 11, 2020 by alyctes

[3below]

The initial ease of turning was the string force aiding the truss rod return the neck to a 'neutral' position. After that you get a bit of easy adjustment where nothing seems to happen, then you get the usual resistance as you oppose the curvature the strings want to create. All is good from your description. With low tension strings like TIs quite a few of my bass necks do not need any truss rod engagement other than a small amount to stop rattling.

[bazzbass]

all this conjecture about the relief in the neck and NOT ONE PIC

pointless