Few things are more frustrating than
when you pick up your favorite guitar
and discover it’s not playing right. Either
the action has “magically raised itself ” or it’s
so low that every note rattles. You wonder,
“What happened to my guitar?”
At some point, the neck goes out of
adjustment on virtually every guitar. The
culprit is typically weather, humidity, or
changes in altitude. When the weather
changes, so does anything made from
wood. Likewise, as the humidity changes,
the wood in a guitar will contract or
expand, and this causes the instrument to
drift out of adjustment.
Fear not! With a few simple tools, you
can adjust your neck and be back in business
in just a few minutes. To illustrate the
process, I‘ll turn to a Fender Stratocaster
with a typical modern truss rod and a
rather unconventional paint job. I call it my
Zombie-Caster (Fig. 1).
Fig. 1. Our project guitar—the Zombie-Caster.
Photos by John LeVan
There are several types of truss rods: single-
action, double-action, and non-adjustable.
Though they work in different ways,
all truss rods are designed to counteract the
tension of a guitar’s strings, which are constantly
pulling on the neck. Left unchecked,
this tension would bow the neck forward.
A single-action truss rod moves the neck in
one direction (Fig. 2). By tightening the rod,
you force the neck into a convex shape known
as “back-bow.” Conversely, when you loosen
the rod, it relieves the tension inside the neck
and the strings will pull the neck forward, creating
a concave shape called “fore-bow.”
Fig. 2. A single-action
truss rod creates back-bow to counteract string
The single-action rod will eventually
run out of adjustment. Once the rod has
reached a fully relaxed position, by itself the
neck won’t offer any more fore-bow. This
limits the adjustability and is a problem if
the neck wasn’t made properly when the
truss rod was installed.
Double-action truss rods force the neck in
either direction (Fig. 3). I’ve used this type of
truss rod in several of my guitars and I really
like them. You tighten the double-action
rod to force a back-bow or loosen it to force
a fore-bow. The key difference between a
single- and double-action rod is the latter has
the ability to create fore-bow. With a double-action
rod, you can actually force the neck
into either a concave or convex shape.
Fig. 3. A double-action truss rod allows
both back-bow and fore-bow.
Non-adjustable truss rods are self-explanatory.
Typically composed of wood, graphite,
or metal, they cannot be manipulated.
They are also referred to as a K-Bar or steel
re-enforced neck. These rods are usually
found in older archtops, classical, and some
Step 1: Gather your tools and prepare
You only need a few tools
for this project, but it’s very important to
use the correct ones. Here are the three
items I use when adjusting a truss rod:
• Action gauge (available from
• Correct neck wrench (typically, this is
supplied with the guitar)
The measurements are very small on an
action gauge, so you’ll need good lighting
to read them.
Step 2: Measure current neck relief.
Before you adjust the truss rod, you
need to assess the neck’s current state.
Measuring the amount of “relief ”—i.e.,
intentional fore-bow to provide room for
a vibrating string—in a neck can be tricky.
I suggest using a light with a built-in
magnifier. You’ll need the magnifier when
taking measurements that vary from 1/64"
(.015) up to 3/64" (.045). These are very
small increments, but just a few thousandths
of an inch can make a big difference
Here is my process for measuring existing
• Tune the guitar to pitch.
• Place a capo on top of the 1st fret
Fig. 4. To
measure relief, clamp a capo on top of the 1st fret
and then hold down the
6th string at the last fret.
• Hold down the 6th string at the last
• Place the action gauge behind the 6th
string, resting on the frets (Fig. 5).
Fig. 5. Using a Stewart-MacDonald action gauge
to precisely determine neck relief.
• Gently slide the gauge from the 1st to
the last fret, taking note of the space
between the fret and string as indicated
by the gauge’s markings.
Write down the greatest distance—the biggest
gap you encounter—from the top of
the frets to the bottom of the string. This
distance tells us how much relief or fore-bow
the neck has. This measurement can vary
dramatically from one guitar to another.
If there is no relief or fore-bow, then
either your neck is dead flat or has back-bow.
This means you need to loosen the truss rod
to add the proper amount of relief.
Step 3: Determine the correct amount
How much relief do you need? This
depends on how you play: If you’re a light
strummer, you only need the minimum
amount of relief. If you strum hard or use a
capo, you’ll need more relief—a larger gap
between the frets and vibrating strings.
For a light-to-medium strummer, relief
measuring about .010 is plenty. This will
also help keep the action low. For an aggressive
strummer (or if you use a capo), .015
to .020 is normal. This will help prevent
string rattle and buzzy notes. Keep in mind
that these measurements are the distance
from the top of the frets to the bottom of
the 6th string.
Step 4: Adjust the truss rod.
There are several different ways to adjust
a truss rod. Some truss rods require a screwdriver;
others use an Allen wrench or even
a socket wrench. Make sure you have the
correct tool for the job!
As for my Zombie-Caster, it has .020
relief, as you can see in Fig. 5. That’s more
than necessary for my playing style and
explains why the action feels so high. Because
I don’t play hard or use a capo, I’ll adjust the
relief to be around .010 (Fig. 6). To adjust
this truss rod, I need a 1/8" Allen wrench.
Fig. 6. Adjusting the truss rod with a 1/8"
Sometimes the access for the truss rod
is at the heel of the neck. If that’s the case,
depending on the design, you may have to
remove the neck to adjust the rod (Fig. 7).
Vintage and vintage-style reissue Fenders,
for example, require neck removal. Of
course, this means remounting, restringing,
and retuning between each adjustment.
That’s okay—be patient and make small
adjustments. It takes time to get this right,
but the effort is well worth it.
Fig. 7. Some necks need to be
removed to access the truss rod.
To add relief or fore-bow, turn the
wrench counter-clockwise. If the neck
needs less relief turn the wrench clockwise.
(If you’re looking directly at the truss rod
nut, you can think “righty-tighty, lefty-loosey.”)
Always retune and remeasure after
Tip: If the truss rod won’t turn smoothly—
stop! There could be a problem with it.
Remember, never force a truss rod. If you
break it, it will cost a fortune to repair and
probably trash the neck. If you’re not comfortable
adjusting your truss rod, consult a qualified
Because my Zombie-Caster has .020
relief, I needed to turn the wrench clockwise
to tighten the truss rod and reduce the gap.
After turning the wrench about 1/3 of a revolution,
the neck was right where I wanted it.
Wrap. If you carefully follow this procedure,
you’ll be able to adjust your truss
rod and keep your guitar playing its best.
Don’t be surprised if you have to make
this adjustment once or twice a year. The
frequency really depends on your climate
and how much traveling you do. And if
you change string gauge, you’ll also want to
tweak your truss rod to accommodate the
increased or decreased string tension.
We’ll tackle another DIY project next
month, so see you then.