How A Truss Rod Works: A Quick Explanation

Ever wonder how a truss rod works? For many players unfamiliar with making adjustments on their guitar, a truss rod is a confusing device that somehow, mysteriously makes their instrument better.

Through the use of a simple analogy, you’ll see first hand the basic principle behind the truss rod and how to adjust it according to what your guitar needs.

Video: How A Truss Rod Works

Let’s say, you know that adjusting a truss rod is supposed to make the neck move either up or down – that is – induce more or less relief along the length of the neck.

But really, the “problem” for most guitarists is either:

1. – “I don’t want to screw it up“… (fair enough, knowing your limits is a very good thing, but not trying is another…)

2. – “I’m not sure which way to turn it“

THE most common statements I’ve heard regarding truss rod  adjustments for years.

And the reason for this article; to shed some light on the basic principles behind what a truss rod is and does to help eliminate the intimidation of the great guitar voodoo unknown.

Sorry, no eye of newt or batwing here, just plain old fundamental mechanics.

Over time, the constant pressure from the strings, combined with seasonal changes in humidity, take their toll on the guitar’s structure compressing the span between the nut and the bridge enough to force the neck into the infamous “banana” shape.

The neck is then referred to as “warped”, “kinked”, “sprung”, “mushy”, “f****d”, etc… all meaning the same thing: it just ain’t right.

In 1921, Thaddeus J McHugh, being assigned by the Gibson Mandolinguitar Company of Kalamazoo Michigan, applied for a US patent: “To provide an improved neck for stringed instruments, which is so constructed that it is not likely to spring or warp under the strains to which it is subjected in use, and one which should warped, may be straightened.” – Source: Google Patents

So, we’ve had this little gem for almost a hundred years, not bad. It was such a good idea it’s become a staple in modern guitar manufacturing saving countless players the grief of a “sprung” neck (provided you know how to use it) – thank you Thaddeus.

Still, being a mechanism with only one visible moving part from our point of view, the truss rod seems… ambiguous.

Truss Rods and Age

Thankfully, even the most cost-effective truss rods are capable of providing some resistance against the ravages of time and pressure. But, there are instances of instruments being tucked away in attics and basements where they languish for years becoming GSOs (guitar shaped objects) permanently lock-jawed into an unplayable state.

A few years back, a cheap old acoustic came in for service that the owner told me was one such instrument – it had been stowed in his attic for years.

Knowing this and having the presence of mind, I warned that adjusting it might not go well; the first order of business being to adjust the badly warped neck.

I found the allen key that fit, give it a modest tug in both directions to try and free it up when it suddenly responded with a fateful “SNAP!” The adjuster had been seized and broken clean off the end of the rod – the only time this ever happened to me, and I’ll never forget it. I also remember how little force it took.

Chances are you’ll never have to experience that – which is a good thing.

Personal Observations

With so many clients posing the same questions on a regular basis, and so did I when I was starting out, I felt compelled to provide some insight on the subject to help pull back the curtain of confusion.

I vividly remember fumbling with my old Les Paul’s truss rod adjuster many, many years ago and not fully understanding the net effect: which way do I turn it?, and what’s supposed to happen?

After some careful research and practical application, adjusting a truss rod became a fairly routine process. Over the years I’ve encountered many different types and quality levels of truss rods. At the end of the day, they basically all work the same way by inducing pressure.

I’ve observed that for most players, simply knowing which way to turn the truss rod adjuster to achieve the desired effect is a good stating point. Hopefully this article has shed some light on how to do just that.