Decoding "Good Action"

Oct 10, 2025 • Dan Holtz, Lakeside Guitar

We've all experienced what we call "bad action" on a guitar or bass. But what is it? What’s bad? I would argue that most players have no idea. My experience is that "bad action" ain't just one thing. It's a collection of problems that can show up in different ways, and sometimes with several ways.

Back in the Saddle

The most common action complaint I hear goes something like this: "It plays fine down here, but it's a beast up the neck." That's a long ramp — strings that climb steadily higher as they approach the bridge, leaving you comfortable in cowboy chord territory but fighting the guitar by the 12th fret.

The first thing to check is saddle height. On electric guitars, this is usually a straightforward fix. Gibson-style bridges offer left and right height adjustment via a thumbwheel or flathead screw. Fender-style saddles adjust individually with an Allen wrench — quick and precise once you know what you're aiming for.

Acoustics are a different story. You'll need to loosen the strings and carefully sand down the bone or plastic saddle. It's slow, deliberate work — and once you've taken too much off, there's no going back. Proceed with patience.

Got a floating tremolo? Brace yourself. Saddle height on a floating bridge is a balancing act between string tension and spring tension. Adjust one and you shift the other. It's manageable, but you need a clear strategy or you'll spend an afternoon chasing your tail.

If you've bottomed out the saddle and the action is still too high, the saddle ain’t your problem, it's just where the problem shows up. The real culprit is likely one of these, and none of them are great DIY territory:

Humidity issues — a swollen or dried-out body can cause a belly bulge, humping the bridge and raising the whole string plane
Misaligned bolt-on neck — usually correctable with a properly fitted shim
Misaligned glued neck — almost certainly requires a neck reset

Bad to the Bone

So far we've been talking about the long ramp — strings climbing as you move up the neck. But there's another kind of ramp that runs the other direction: lateral ramping, where string height varies from bass to treble across the same fret. It can shows up at either termination point: the bridge or the nut.

At the bridge, a lateral ramp is a little more subtle to detect, but super common in acoustic guitars. Look down the low E string while you're playing — it might look too high. Then flip the guitar and look at the high e — it could look pretty low and tight. You can self-diagnose this by looking down the neck toward the bridge and checking where the bottoms of the strings meet the top of the saddle(s). Do the heights descend toward the high e? Then look up at the nut — same story there, though the nut's a little harder to read. Every string should be the same distance from the fretboard, bass to treble. No short ramps.

At the nut, the issue is a bad slot cut. Those little slots are filed by hand with specialized files — I've got three sets of them, and they're stupid expensive. The reason precision matters: string tension is at its highest right at the nut. Any extra height in those slots makes a disproportionately big difference in how hard you have to press. When slots are cut too high, open chords become a real workout and your callouses will thank you (your audience won't). Cut them too low, and you get buzzy strings. It's a narrow target, and it takes practice to hit it consistently.

It's Lump!

I like to describe this kind of bad action as "lumpy" because that's how it feels. It's also "stealth" bad action – it can look like good action, but it feels like bad action. Strats often arrive in this condition, but other guitars, too.

At the nut, it's nice and tight. Up higher, fret 12 or 17 (acoustic vs. electric), it looks pretty lean and mean. Yet, something is not right. It just doesn't play well. This is the stealth bad action, and it's usually caused by an inferior setup.

Here's what's probably happening. Someone attempted to improve the action, but the true issue was not properly addressed. Maybe the nut slots were cut too low. Maybe someone set the saddle to low. Or maybe, there are some uneven frets. None of that was considered. Instead, the intrepid "truss rod ranger" came to the rescue, with allen wrench or nut-driver in hand!

Look, we are led to believe that the truss rod is a magical piece of equipment that can be mysteriously adjusted to solve any manner of playability issue. Not true, but the myth persists. The truss rod has just one, single purpose: to true the neck as close to straight as possible. Any amount of back bend in the neck is called "relief", in that it's relieving string tension. This is not to be confused with bowing, when the neck bends upward. That's never acceptable.

In any case, when the truss rod is allowing too much relief (i.e. back bend in the neck) you get this deep zone in the middle of the neck where the action feels really spongy. Furthermore, it divides the guitar into 3 zones with the bad action right in the middle. That "lumpiness" as you move up and down neck is very distracting and degrades the playing experience.

How Sweet It Is

Here's my proposal to you: good action on a stringed instrument is when it feels as close as possible to the same everywhere on the neck. When your fingers don't have to adjust to different amounts of string tension (i.e. pressure required to press them down) you stop thinking about the guitar, and you start thinking about the music.

In order to achieve this effect (and yes, it is just an effect), you have to take into consideration the physics of a metal wire being stretched and then bridged across two points. Your fretting hand is playing from one termination point (i.e. the nut, and the highest tension) to the middle (i.e. the 12th fret, and the lowest tension) and maybe a bit beyond middle.

If the string height were literally the same everywhere, it would not feel even. The strings must be lower at the termination point (i.e. the nut) to accomodate for higher tension, and higher in the middle (12th fret) to accomodate for lower tension. The question is, how much?

Additionally, there's the cylinder effect. Look up the neck at the edge of your fingerboard, where the radius is very visible Strats are often 7.25"-9.5", Martins are usually 12"-15". What does this mean? Imagine continueing to draw an entire circle from the radius of your neck. If you do, the resulting circle from a Strat would be 9.5" diameter (or 7.25" if it's got a vintage style neck). This is a rounder neck. Higher numbers are flatter necks.

OK, now imagine a cylinder with a ruler laid lengthwise across it, end-to-end. It's making contact with the cylinder everywhere. Now, turn the ruler slightly. Now it's not making contact at the ends. It see-saws on the curvature of the cylinder.

Your strings are experiencing the same effect. Why? Because your neck is wider at the bottom than at the top. The strings are crossing the middle of the round. This complicates things because it means that the middle of the guitar is actually higher relative to each string, especially the outer strings.

This is where truss rod relief comes in! More dramatic radii (lower numbers) require more relief in the neck. So, like a Strat might need .007"-.010" in neck relief, whereas a Martin might need only .003"-.005". Seems like a tiny difference, but in luthier-land, that's a big difference.

So, you have to balance the heights of the termination points (i.e. nut and bridge) with the relative center-height of the guitar (i.e. the truss rod) to achieve this effect of even playability and tension everywhere. In other words, you have to create a long ramp – but at a strictly controlled angle.

Finally, but not to be dismissed, you should avoid (at all costs) the short ramp. Every string should be the same distance from the fretboard from bass to treble. Again, this has to do with the fingerboard radius. If the nut slots were cut flat across, the middle strings would be closer to the fingerboard than the outer strings. More often, as above, the bass strings are set higher than the treble strings. IMHO there is zero reason for this. No short ramps!

A Little Less Talk (A Little More Action)

Now that you have some familiarity with the four horseman of bad action, and some physics and philosophy around good action, let's get specific. There is a sweet spot – it's not hypothetical, nor is it mysterious. Amazingly, it's the same for pretty much all guitars and basses – both electric and acoustic.

This golden ratio is a simple formula, but in practice it can be more aspirational than achievable. Small variations are often necessary due to the unique limitations of any given instrument. Wooden instruments change with moisture conditions, heat, time and the amount of play they have absorbed. I always aim for the same constants, and I adjust to maximize what any given instrument is capable of.

OK, so I'll shut up and give you my formula. It's pretty much the same for every guitar and bass, with adjustments in either direction based on the unique conditions of that instrument.

Golden ratio (1:4):

.010" truss rod relief
.020" @ first fret
.080" @ 12 fret (or 17th fret for electrics)