i heard a snap while adjusting the truss rod

[Bardley]

There is no harm at all in altering the action with a truss rod adjustment. It presents no more risk to the bass than adjusting the rod for any other reason.

That said, it is not a very good idea. Action is, in fact, a combination of neck relief and saddle height. You have to have them both right. So, using only relief would be akin to using only the saddles. You can tweak the saddles all you want but if the relief is wrong, you are going to get limited results. Same goes for tweaking the rod and leaving the saddles alone.

+1

You can't have one without the other.

 

[king_biscuit]

There is no harm at all in altering the action with a truss rod adjustment. It presents no more risk to the bass than adjusting the rod for any other reason.

That said, it is not a very good idea. Action is, in fact, a combination of neck relief and saddle height. You have to have them both right. So, using only relief would be akin to using only the saddles. You can tweak the saddles all you want but if the relief is wrong, you are going to get limited results. Same goes for tweaking the rod and leaving the saddles alone.

Adjusting action with the truss rod is a bad idea for a number of reasons: for example, a neck that has too much underbow presumably for higher action is at risk of taking on a permanent warp if left that way. A neck that is backbowed for lower action -- at least in the case of a rosewood board risks loose frets and neck warp. Also, a neck that is already backbowed and then adjusted to further to lower the strings puts the poor truss rod at great danger of serious damage -- it sounds like the op nearly found out all about this. I believe that I mentioned to the OP in my first reply to him to set the neck for proper relief and then set bridge for desired action.

 

[Bassguy1]

Here is the proper way to set relief, string height and intonation. A great set of videos that make it very simple to do by oneself. Scroll down to LESSONS section and check out the 4 how-to CRUZ TOOLS videos.

http://www.bassplayer.com/Video

 

[Tusec]

Yes, of course you have to use some judgment and avoid doing extreme things if you set the action with the trussrod. But for minor tweaks it's perfectly safe and much quicker than fiddling with all your saddle screws and having to reset the radius and all that. I'm sure that's why the Ernie Ball guys recommend this approach.

And I disagree that saddle height and relief have to be changed together. I'll bet everyone here has adjusted their saddles at one time or another (and probably many times) without feeling the need to adjust the rod, and gotten good results. I know I have.

It seems counter-intuitive and maybe even a little sinful to use the trussrod alone to adjust the action, but there are two reasons why it works:

1) There is a range of acceptable relief settings.

2) Small changes in relief have the same effect as large changes in saddle height.

The result is that the truss rod can have a broad range of effect on the action while staying inside the limits of acceptable relief.

Here's a quick and dirty graphic to help visualize...

It shows two things at once: 1) the relief required for a given action, and 2) the saddle height required for that same action while leaving the neck straight. What you see is that it takes much less relief to create a given action than it does saddle height. If this drawing is anything like right (and I'm open to peer review on all of this), the ratio of the effect of saddle height to relief is about 1 to 3 .

Keeping the 1 to 3 assumption, this means is that adding or subtracting 1mm of relief is equal to moving the saddle height 3mm in either direction, which is 6mm or about 1/4" of total range. Since most bridge saddles only have a range of about 1/4", you can see why adjusting the relief works: all it takes is a tiny amount of adjustment to cover the whole range.

So if you can live with about +/- 1mm of change in relief, which most people probably can, then you should be fine adjusting your action with the truss rod.

The big caveat is that the truss rod method is for adjusting a bass that's already been properly setup, not for doing the initial setup. IIRC this is what the Ernie Ball FAQ is referring to when they recommend the truss rod method -- adjustment, not initial setup.

 

[KEVINTHES]

my question is though how do metal saddle pieces tighten up over the years ya know? the problem ended up not being the necks relief but the saddles being too high. this bass has NEVER had a saddle adjustmen since i first got it of course and ive relied all on neck adjustments to change things on it. however i have such a dainty touch when im playing bass that i didnt notice any buzzing from the neck being too straight(which it was, there was not nearly enough for a business card to pass through when the 2nd and 12th fret was pressed down.

so i guess im wondering...how does the metal pieces in the bridge shift to become tighter over time? especially in a stable basement enviroment.


on the other hand the enviroment around chicago is not anywhere near stable, i heard the humidity inside drops 50% in a heated house when the temperature drops 20 degrees outside. and winter here has such temperature shifts very often.

 

[king_biscuit]

Yes, of course you have to use some judgment and avoid doing extreme things if you set the action with the trussrod. But for minor tweaks it's perfectly safe and much quicker than fiddling with all your saddle screws and having to reset the radius and all that. I'm sure that's why the Ernie Ball guys recommend this approach.


The big caveat is that the truss rod method is for adjusting a bass that's already been properly setup, not for doing the initial setup. IIRC this is what the Ernie Ball FAQ is referring to when they recommend the truss rod method -- adjustment, not initial setup.

EB doesn't limit this approach to "minor tweaks," nor to basses that are "properly setup," whatever that means. In fact, there are not any real caveats on the EB website. From the EB FAQ on the website:

"Could you tell me Music Man's StingRay factory settings for relief, string height, and pickup height?"

"First of all - almost all of the adjustments to string height can be made with the truss rod"

Really, EB, almost all adjustments? There is no qualification that this is limited to a bass that is otherwise at factory spec. Nor is there any explanation for the unwashed as to when "a particular" height adjustment is more than the truss rod alone can provide.

 

[Tusec]

EB doesn't limit this approach to "minor tweaks," nor to basses that are "properly setup," whatever that means. In fact, there are not any real caveats on the EB website. From the EB FAQ on the website:

"Could you tell me Music Man's StingRay factory settings for relief, string height, and pickup height?"

"First of all - almost all of the adjustments to string height can be made with the truss rod"

Really, EB, almost all adjustments? There is no qualification that this is limited to a bass that is otherwise at factory spec. Nor is there any explanation for the unwashed as to when "a particular" height adjustment is more than the truss rod alone can provide.

Hm, I was thinking EB was clear that it was for basses at factory spec but I guess not. Either way, it's fairly obvious that this would be the case. But you're right, if the FAQ is intended for the unwashed, it should be more clear.

By properly set up, I mean a bass that would otherwise be at factory spec.

 

[king_biscuit]

i have such a dainty touch when im playing bass that i didnt notice any buzzing from the neck being too straight(which it was, there was not nearly enough for a business card to pass through when the 2nd and 12th fret was pressed down.

If you play with a light touch and want low action, a business card's worth of relief pressing 2nd and 12th fret is too much. Try to get the neck nearly dead straight, so that if you hold down the string at the first and last fret, there is just barely a bit of light between the seventh fret and the string. Adjust the bridge saddles from there for desired action. Next set the intonation and pickup height.

 

[ehque]

1) There is a range of acceptable relief settings.

Not if you're aiming for as low an action as possible. My strings barely clear the 7th and 12th when fretted at the 2nd and 24th fret.

 

[Tusec]

Not if you're aiming for as low an action as possible. My strings barely clear the 7th and 12th when fretted at the 2nd and 24th fret.

For the lowest possible action, you would set the truss rod for zero or near zero relief. For higher action, you would add a little more relief.

The point is that you can achieve either of these by adjusting the truss rod alone -- assuming the bass is otherwise properly setup.