Maple neck back bow problem

[christianb]

I just bought a new 4 string Marcus Miller j-bass from ebay. When I got it the strings where tuned to pitch and the action was nice, but the neck had almost no relief (got some fret buzz on the last 8 frets) otherwise it looked great, very straigth and good looking neck. So I started to loosen the truss rod, and here the problem occured. The truss rod was already set to it's most loose position, so the only thing I can use it for now is to give the neck bigger back bow. I tried to bend the neck with increased string pressure for a couple of days, but it did not work of course( it always go back when I tune it). That have to be done when the wood is fresh i guess. If I want to get rid of the buzz with high action I have to put it much higher than I prefer. It's a bolt on maple neck by the way. I really need just a tiny bit more relief.
Any ideas? I will try to change strings to a bigger gauge this week, maybe to take it to a luthier and se what they say. In worst case Im thinking of changing the neck.

 

[allenhumble]

If it is new it should be under waranty still. Contact the seller or Fender.

 

[FBB Custom]

The neck has a one-way rod?

Step 1 is see if it is under warranty. If not, then you (or someone else) will have to heat bend the neck.

 

[Al Heeley]

You sure you don't need a little fret - levelling to take out that buzz?

 

[pilotjones]

When you say that there is buzz on the "last 8 frets," do you mean up by the body? My understanding is that the tuss rod has little if any effect up in this area, whereas the bridge saddle height has definite effect. And raising the bridge would also cause more forward bow bending moment.

Luthiers care to comment?

 

[reddogbass]

Add a small shim (.004-.005") to the headstock end of the neck pocket, effectively raising the headstock slightly in relationship to the bridge. This is a very common fix, and done all the time. I prefer this method to adding "neck relief."

 

[SDB Guitars]

Back when I was in college, I had a Rickenbacker that was so dead flat that it buzzed a little (it was my father-in-law's... I still miss that thing).

One summer I loosened the truss rod and braced the instrument with some tension on the neck so that it forced a little relief in it, then put it in a storage unit (in Oklahoma, with no temperature or humidity control) for a few weeks while I went on a road trip. When I came back, I let it re-acclimate to my apartment, and it was perfect!

 

[christianb]

Im not hundred percent sure it has a one way rod, didn't dare to wind it to far after loosening it. And the fender site doesn't say. But it's a reissue from -77.

It plays really good if I play it gentle, but if I start fingering with power there is buzz, especially on the upper frets(on the body). Don't think I need a leveling since the bass is brand new, I don't have any tools for measuring though.

With normal string pressure and the rod set to minimum pulling, the neck is very straight with a small relief only visible if I measure with the strings. I'm not sure but I think it will go into a small back bow if I loosen rod and strings. Otherwise the neck is beautifully straight.

Sure I tried with raising the action from the bridge but this results in a compromise, and I don't want it to high. Just feel that for my way of playing I want a tiny bit more relief, as there is hardly any right now.
I like the shim idea! I will try that if it doesn't work with bigger gauge strings.
The heating idea feels like a last resort. The finish is very concealing as well so I assume that would make it hard to moisten up the wood. And forcing the neck would take time (like to play), if at all possible, it really likes the position it's in.

I feel a bit worried about the rod, since I don't know how it's constructed. Can I fully loosen it and then try to bend a neck and after that still expect it to tighten? Or might it stay loose forcing me to open up the neck?

thanks for all help!!

 

[Al Heeley]

I loosened the truss rod and braced the instrument with some tension on the neck

Some would see that as a cruel torture of a fine instrument, but I guess it was for its own good in the end.

 

[Nelson Guitars]

Before installing the shim mentioned above, remove the neck and check the neck pocket. Very frequently you will find excess build up of finish in the "corners" that if removed will tilt the neck down just enough to allow the strings to stop buzzing. This will also create a better mechanical connection between the body and the neck.

The truss rod helps to shape the neck as well as keep it from moving with changes in humidity. It will not help and should not be used to adjust action or fix the problem you describe. I recommend first checking that the neck fits the pocket well (see above). Next, verify the truss rod has at least a little tension. A loose truss rod is a rattle waiting to happen. Then verify the relief is within tolerance. After all that if you need higher action to keep the buzz away then try height adjustment at the bridge. If the adjustment is too much then and only then consider shimming your neck.

I know lots of builders will reach for a shim much earlier than I describe but I feel that a bolt on neck is already disconnected enough from the body, why distance it further through the use of a shim.

If the frets are not level and can not be made level with a minor set up, then the neck might be able to be straightened with heat and pressure. Only an experienced luthier should attempt this. You can really screw stuff up if you don't do this right.

Obviously if you have a warranty that would be the first place to go.

Greg N

 

[pilotjones]

The truss rod helps to shape the neck

Yes.

as well as keep it from moving with changes in humidity.

Really, now. If anything, the fact that wood reacts to moisture changes while steel does not, may serve to have the opposite effect.

It will not help and should not be used to adjust action

?????????
Maybe I've got some definitions wrong, but to me the action is the relationship of the straight-path unfretted string to the line formed by the crowns of the frets, and is therefore a combined result of the neck relief shape (produced in conjunction with the truss rod), and the saddle height.

 

[christianb]

The truss rod helps to shape the neck as well as keep it from moving with changes in humidity. It will not help and should not be used to adjust action or fix the problem you describe.


Greg N

Thanks for the instruction of how to use the shim Greg!

although I haven't thought of using the rod to change action, only to increase neck relief. If I change action on the bridge right now it will have to be set much higher than I want to.
Maybe you can tell me how the truss rod works, I'm not going to heat bend the neck myself, and don't think it's needed. But when done, I suppose the rod must be fully loosened, does it ever happen, that the rod stays loose and will not tighten again?

 

[73jbass]

Wait a second,if it's a 3 bolt neck,you can adjust the pitch on that neck. Look in an owners manual and see what it says.

 

[Nelson Guitars]

Pilot,
Some of this has to do with the limitations of words and how they are interpreted by those writing them and those reading them.

The stability of the truss rod in counter tension with the wood in the neck will help stabilize the entire system. This is also true about laminations vs. one piece necks. One could argue that removing wood to accommodate the rod actually reduces the strength of the neck, but the addition of the truss rod more than counters the loss of wood mass.

I have also heard the argument that the truss rod itself is flexible and less stiff than wood of the same dimension. This is true to an extent, but just shows they don't understand how the rod is working. In short, think of a spoke on a bicycle wheel. Very thin and weak, but the bike hangs from the spoke pulling the one above and not crushing the one below. Does that make sense?

Action is the relationship of a straight string over the FB and relief is the curvature of the FB. They are different by definition but related. Changing relief has the side effect of changing action. My point is that you should not miss use the truss rod as the primary way of adjusting action. If the relief is appropriate to your playing style then action should be adjusted at the bridge.

Remember that action and relief are relative to where your are fretting and not just for open strings. From the description above it sounds like perhaps there is too much relief. Imagine a significant relief in the FB with reasonable action when played at the 0-5th frets. But when you reach the 6th the string is depressed so far that the new "straight line" between the fret and the saddle causes the string to hit the 12th or the 14th fret. Now flatten the relief a bit and the whole thing starts to buzz because the nut has "lowered" itself relative to the saddle. Raise the action by raising the bridge or changing the neck angle and you now have the same action but a flatter FB and the buzz at the 12th is gone.

I am not saying that this is the solution to the original question. There are many possibilities. It takes a good understanding of how these things work and a bit of experimentation sometimes to set everything up right.

Greg N

 

[Nelson Guitars]

Maybe you can tell me how the truss rod works

There are many different rods out there. The most common I see these days consists of 2, 1/4" rods set into threaded blocks at each end. One is right hand thread and the other left hand so that when you turn the rod it forces the blocks apart or draws them together. Since the other rod is static this creates compression or tension between the two. Since they are held in place by the channel and the FB that tension puts pressure against the neck and FB.

Did that make sense? Remember, a truss rod is not unbendable or inflexible. It is adjustable tension that allows the luthier to vary the neck shape after all of the tension is applied. Put a different set of strings on or change tuning and the relief will change whether you have a rod or not. Having a rod only allows you to make a subtle compensation if needed.

Greg N

 

[christianb]

I found the problem. Thanks for mentioning the pitch thing. I removed the neck today while changing strings, and found out that someone adjusted the pitch. It was to far out, so I adjusted back into the body. And now the neck played so nice it couldn't be anny better! So no shim needed. Thanks! And exscuse me for being unaware of the pitch.