In this video I teach you a several important lessons about your bass truss rod. In the last part of the video I show you how to replace a truss rod nut.
What is a Truss Rod?
The truss rod is a tension rod that runs inside the neck of your bass.
The tension of the bass strings pull or bow the neck in one direction.
Think of a bow and arrow. Imagine that your bass neck and strings are like the bow and string.
The truss rod counteracts the tension that the strings place on the neck and pulls it back in the other direction. That straightens your neck and allows your bass strings to stay closer to the fingerboard.
The Truss Rod Nut
Truss rods have a truss rod nut at the end. You turn it to tighten or loosen the tension of the truss rod.
Let me show you against a straight edge, how the truss rod works. When the truss rod is loose, you'll see that it's straight. And when you tighten the truss rod nut, it makes the truss rod bow or curve.
Some truss rod nuts are welded on and they can't be replaced. Others are removable and replaceable. You'll need to research your particular bass to be find out.
Truss Rod Nut Tools
Depending on the nut, you'll need a certain kind of tool to turn it. It's often a hex key or Allen wrench as they're called.
But sometimes you need a nut driver or a screwdriver. It's very important to have the right tool to turn your truss rod nut. We will discuss tools more later in this article.
Truss rod nuts turn like common nuts. Remember righty-tighty; lefty-loosey. Turning it right, makes it tight and turning it left loosens the truss rod.
Truss Rod Problems
If you don't know what you're doing when you're adjusting your truss rod, you can cause some problems. Some truss rod problems can be pretty bad news.
Broken Truss Rod
One problem is breaking the truss rod by over-tightening it. Replacing a truss rod requires removing the fretboard off the neck. That's a very tricky and expensive repair. What most people end up doing is just replacing their entire neck. Sometimes a new neck won't make sense financially and it's the end of the bass.
Truss Rod Lesson #1: Be Gentle
The first important lesson is be gentle when you adjust your truss rod. Even a quarter turn can be quite a bit. Take a pencil and mark the 12 o'clock point so that you know where you started. You don't need to be in fear of adjusting it. Just don't go crazy turning it a lot. If you are setting up your bass and you feel like your truss rod adjustments aren't helping, take it to a guitar pro.
When you adjust your truss rod, loosen the strings completely and loosen the truss rod some before tightening it.
Stripped Truss Rod Nut
A more common truss rod problem is a stripped truss rod nut.
If the truss rod net requires a hex wrench, stripping it means that the six flat sides of the hex-shaped hole have been rounded off and the Allen wrench can't grab anything to turn the truss rod nut. And, that means you can't adjust the truss rod.
Removable Truss Rod Nuts
If your truss rod nut is removable, this shouldn't be too difficult to fix. You'll need to track down the correct replacement nut. Then you have to figure out how to remove the old nut and replace it with the new one.
Welded-On Truss Rod Nuts
If your truss rod nut is welded on it might be more trouble. How can you tell if it's welded on? Well, it may be hard to tell by looking at it. You should research your particular bass, make model, and year to find out. You might have to ask the manufacturer, or you might just need to take it to a guitar repair person.
What Makes a Truss Rod Nut Strip?
One reason a truss rod nut will strip is from applying too much turning force with the hex key.
The nut is often made from a soft metal on purpose so that you're more likely to strip the nut than break the truss rod.
Truss Rod Lesson #2: Don't Tighten a Frozen Nut
Another lesson: if the nut is hard to tighten or frozen, don't force it. Just stop and take it to a guitar repair shop. And don't take it to a music store. They might strip the nut, too! I've had numerous students who have had their instrument damaged by someone at the music store. Find the top local person who only does instrument repairs from their dedicated shop.
Wrong Size or Bad Wrenches
The more likely way a truss rod nut gets stripped is someone using the wrong size wrench or a poor-quality wrench to turn it.
If the wrench doesn't fit tightly, it might turn and round out the hex-shaped hole, even without much force. This may happen all at once, or gradually strip the nut over time.
Truss Rod Lesson #3: Use a Quality Wrench
Another lesson: Never turn a wrench that doesn't fit very tightly. Wrenches and drivers should have little to no wiggle room. If it has some play, don't turn it. Take it to a pro who has all of the good tools. Your bass may have come with wrenches, but they may be cheap, poorly-sized wrenches. It's even possible that the wrong key ended up in the case at the music store. You never know.
I've found these Bondhus Allen key sets (affiliate link) to be perfectly sized. Don't buy cheap tools which can lead to expensive repairs for you later.
Truss Rod Lesson #4: Check the Right Size Wrench to Use
Here's the next lesson about your bass truss rod: Look up the truss rod nut wrench size for the make, model and year of your bass. Keep in mind that even the same model might change sizes from one year to another.
What often happens is someone uses a metric size wrench that feels like it fits, but they should have used an Imperial size wrench (or vice-versa). Don't guess the wrench size!
Replacing a Stripped Truss Rod Nut
I got a really good deal buying a used G&L L-2500 (excellent bass) from someone I knew. It played perfectly, and I didn't bother to inspect the truss rod nut. Of course, it was totally stripped. Luckily it's replaceable for this year bass. Watch the video to see me go through the process of replacing the truss rod nut.
Truss Rod Lesson #5: Inspect the Truss Rod Nut When Buying a Used Bass
Here's another lesson: When buying a used bass check that all of the nuts screws and adjustable parts are in order, the truss rod is probably the most important one to check out since repairs can be pretty expensive.
Tools to Replace a Truss Rod Nut
If your truss rod nut is stripped and it's replaceable, there are several ways to remove it.
A Good Wrench
If it's not too badly stripped, sometimes a quality wrench will grab it enough to turn it and remove it.
Torx bits are a kind of six-sided bit. Sometimes they catch where an Allen key doesn't.
Easy-out bits have a reverse thread on them that, when turned inside a hole, grab the sides and extract the nut. These bits are also called screw extractors and can be found at auto and hardware stores. Beware of cheap ones. They may break off inside your truss rod nut and cause a new problem for you.
Grinded Larger Hex Key
Another solution is to take the next size up hex key and grind or taper it to fit tightly in the hole.
The Gripper Wrench
The luthier shop Stewart-MacDonald sells tools specifically designed to remove truss rod nuts. They make the Gripper wrench in common truss rod nut sizes. This is what I used in the video. It is a tapered hex key. Instead of using it to replace a nut, you might just use it to turn your truss rod.
Cut Slots for Screwdriver
If none of those solutions work, you may be able to cut slots in the surface of the nut to use a screwdriver to turn it. This might be hard depending on the accessibility of the nut and what tools you have. At this point you should take it to a pro.
Installing a New Nut
Once you've removed the old, stripped nut, installing the new nut is very easy.
I suggest adding a little dab of grease (wheel bearing or lithium grease) with a toothpick to the truss rod and on the threads inside the new nut.
If your replacement nut came with washers, put them on under the nut. Washers help distribute the load placed on the bolt.
Once your new truss rod nut is installed, check that you can adjust the truss rod and go set up your bass!
Use quality tools.
Verify the right size wrench to use.
If the wrench doesn't fit tightly, don't turn it. It may strip the nut.
If the nut is stuck or frozen, don't turn it.
Inspect all of the adjustable parts when buying a used bass. Make sure they turn--especially the truss rod nut.
I hope this has given you insight into your bass truss rod and it will help you avoid any truss rod problems in the future.