Adjusting the truss rod
To hear a lot of people talk, you'd think that the long, thin
piece of metal we call the truss rod was a cross between the Holy Grail and a Plutonium
fuel rod. Yes, you do have to take care when adjusting it and it can break, but if you
approach the task with a little respect for the rod and some common sense, there's no
reason why you can't do this job yourself. Having said that, if you're in any doubt as to
what you're doing, then leave the job to a competent guitar tech. It isn't the most
difficult adjustment in the world, and, provided no work is required on the frets, should
be quite inexpensive.
The truss rod is essentially a long metal rod that is inserted into
the neck of the guitar and fixed. Tightening and loosening in it flexes the neck and
allows curvature to be applied to the neck, altering its characteristics and, hence, its
playability. Before I describe this adjustment, a few caveats.
1) It may be, that after adjustment, the neck isn't quite right and
you may need to look elsewhere to solve the problem. The frets may need stoning, for
example, which is outside the scope of this series of tutorials.
2) Try and get hold of the factory spec for your guitar - Fender
actually have theirs here - and see how a standard
truss rod set up suits you. It's a good basis on which to start, and you can always
deviate from it.
3) Be aware of the advantages and benefits of the various sorts of
"action". A very low action means that bending is slightly more difficult and
the sound has less body. On the other hand, the strings are much easier to fret. With a
high action, the reverse is true. I know that there are a lot of SRV fans out there, and
he played with very high action, which explodes the myth that a low action is
always the one to shoot for.
When to check the truss rod
The rod needs to be checked whenever you string the guitar,
although if you use the same strings - brand and gauge - you can make the checking
intervals a little further apart. Also, because wood and metal expand and contract
according to temperature and humidity, you may find that the neck shifts according to
these factors. Also, if you become aware of buzzes that weren't previously evident, it's a
good idea to check the neck.
How to check the truss rod
Rest the curve of the bass bout on the floor, and sight down the
neck towards the body, looking along the edge of the fretboard. then flip the guitar over
onto the treble bout and repeat the operation. Observe how the line along the edge of the
fretboard runs. If it seems to curve so that it bulges out away from the body, the neck
has a backbow. If it runs the opposite way, the neck has relief. (For those of you who are
familiar with trussrods, I know that there are other conditions that I haven't mentioned,
but I haven't got the time to write a book on the subject. I'm just outlining the most
common truss rod states.) It may be that you see that the neck is dead straight, of
course.
So, to sum up. you have three main neck states:
a) relief
b) backbow
c) dead straight
Here's a pathetic diagram I drew to help you visualise them.
If the neck is dead straight, and you have no buzzing and you like
the way it feels, it's pretty safe to assume that your truss rod is adjusted just right.
Most techs try and shoot for a straight neck. Even if you have a little buzzing, if you
don't hear it when it's plugged in - assuming that it's an electric, of course - then you
can leave it. Not all buzzes will sound through the amp. If it still buzzes when plugged
in, then this doesn't necessarily mean that it's the truss rod that requires adjustment.
You might find your problem is solved by raising the bridge or bridge saddles. If this
doesn't work and you don't eliminate buzzing by adjusting the rod - more on that below -
then you may need some attention to the frets.
(The lesson to be learned here is that all the various stages of
adjustment - the nut, the bridge, the rod, etc - are interdependent and adjustment of one
of these factors on its own may not be sufficient to achieve the set up you're after.)
If the neck has some relief and you're happy with it, then you can
leave it alone. However, if the relief is too pronounced, causing a very high action which
causes intonation problems when you fret a note, then the neck will need straightening by
tightening the trussrod.
If the neck has a backbow, this can cause some of the higher notes
to fret out. You may find that when you play say, the B string at fret 5, the string is
fouled by the higher frets and the sound of the note isn't clear. The truss rod will then
need to be loosened to apply some relief.
Where to adjust the truss rod
This differs from one guitar to another according to brand, model
and type. Gibsons have the adjustment end of the rod under a small plate on the headstock.
Some Fenders have the business end here as well but with no plate. Others have the
adjustment end where the neck joins the body, in which case you have to remove the neck to
adjust it and keep on fitting it back and taking it off until the rod is right. I'm not
going to deal with such adjustment here. Some acoustics have the adjustment area inside
the guitar where the neck joins on. There are also various methods of adjustment. Some rod
ends have a screw slot, some a nut, and others a hex slot. So, you'll need a screwdriver,
a socket of some sort or a hex key. Obtaining the right hex key can sometimes be a
problem, but the right one's out there somewhere!
How to adjust the truss rod
OK - this is the moment you've all been waiting for!
Using the right tool and a well-fitting one as well (you don't want
to mess up the slot or nut shoulders!) insert it into the truss rod end.
If you want to apply relief to the neck you loosen the rod by
turning the rod end - the nut, slot, whatever - to the left, or anti clockwise.
If you want to straighten the neck and eliminate backbow, tighten the rod end to the right or clockwise.
Remember - "righty tighty"!
Apply a one-eighth turn at a time and sight the neck as described
above. If the neck is how you want it - stop! If not, apply another one-eighth turn and
sight it again. Repeat until the neck looks right.
If the rod won't shift, don't keep on trying to turn it. Take it to
a guitar tech. Similarly, if it squeaks or grates, leave well alone and take it to -
you've guessed it! - a tech.
The biggest danger is over tightening. In this case, the worst
scenarios are stripped threads on the rod, or even a snapped rod. In such cases, the
repair can often be more expensive than buying a new guitar. However, you have been
warned! If you're in any doubt about your own competency to do this job, take your guitar
to a tech and if you encounter a truss rod that won't co-operate, do the same!
Just use a little care and common sense and you should be OK.
I realise that this tutorial is little more than an outline.
However, for those of you who want to learn more about this aspect of guitar maintenance
and everything else you can do yourself, the best book I've found is "Guitar Player
Repair Guide" by Dan Erlewine. It's a fantastic book with lots of tips and practical
advice from a guy who has looked after some of the greatest players' instruments.
Good luck!
Guitar set-up tutorials - Overview