Neck keeps bowing despite adjustment

[Welshbassist]

Hi all

Got a bit of an annoying issue with the neck of an older Fender style p bass with truss rod access at the heel. Since I bought it around six months ago it's had quite light strings on and if anything it had a bit of back bow. Recently I bought some 105-45 flats that are much higher tension. After I put them on as expected the neck bowed forward a fair so I figured I'd set it up for the new strings and and went ahead and adjusted the truss rod.

While I've been able to straighten the neck a fair bit - there's definitely way less relief now - what I've noticed is that A) the nut at the heel is incredibly stiff to tighten and B) the neck keeps returning to almost the same position as before I turn it within an hour or so. I'll get around half an hour of absolutely perfect action before it seems to slip back. It's definitely doing something but in comparison with my newer USA Jazz a quarter turn doesn't seem to do much.

 

I've gone through four quarter turns over the last few days and the nut is now getting tough to turn to the point I'm a bit uneasy as I don't want to muscle it and damage anything. I'm happy to take it to a local luthier if needed, but I'd be keen to hear any suggestions about what I could try at home first.

One last point is that I can't for the life of me seem to get one of the tone knobs off to remove the pickguard so I have to take off the neck to adjust the truss rod - not sure if this might be playing a part but figured it worth mentioning.

[Hellzero]

Removing the neck each time you need to adjust the truss rod means modifying the tension in the neck twice, so it's the most inaccurate way to do, for sure.

 

The quarter turn a time then waiting a day and start again is a big myth, you can set up your truss rod immediately to the desired tension if it turns easily.

 

I would do two things if I were you.

 

First : remove the nut of the truss rod and put some graphite grease on the truss rod thread to allow it to move flawlessly.

 

Second : go to a luthier and ask him to make an access to the truss rod (a little routing) at the heel end of the body.

 

And you can set up your truss rod at the strings tension, there's no need to slack the strings before doing that as it will modify the overall neck tension and getting the issues you mention.

[Stub Mandrel]

I have a Squier jazz that showed the same symptoms, altough it took a few days to bow.

 

I realised the end ancor of the rod was moving, crushing the wood.

 

It is, luckily, headstock end adjustment. I took the neck off expecting to have to drill into the back of the heel to find the anchor,  but the skunk stripe was about 5mm short and i could see the anchor in the gap.

 

My kill or cure remedy was a cc or two of cyano acrylate into the hole (with truss rod slacked right off). The idea was to strengthen the wood where it was being crushed, not to glue the truss rod in place. I also added a washer under the nut to restore the full range of adjustment.

 

I gave it a day to set  and readjusted after a week. Since then over two years I have made a couple of minor adjustments, including slacking off so it seems to have worked.

 

Not sure how you would do this with heel adjustment. Drill a hole and then plug it? Its pretty drastic, but as a last resort?

[NancyJohnson]

26 minutes ago, Hellzero said:

The quarter turn a time then waiting a day and start again is a big myth, you can set up your truss rod immediately to the desired tension if it turns easily.

 

 

While I'd concur with this, I feel the advice is more of a cautionary thing; the approach of leaving to let it settle should perhaps be more a case of allowing the neck material/glues/finish etc to settle.  While it's unlikely you'll experience failure, truss rod adjustment should be little and not very often rather than lots once in a whwile,

[mybass]

I think getting a luthiers repair shop to just look at it may yield a conclusive result. When you had light strings on, the neck had some ‘backbow’, when heavier strings where on it was the opposite….? That’s quite dramatic movement really and a first thought was obviously the rod isn’t doing its job but maybe just maybe it’s actually broken internally and although it isn’t rattling (but go ahead and give the back of the neck a good hand palm slap and listen) adjustment will be of little use.

I had a new Fender years ago where the neck would not be straight. I couldn’t adjust it enough and I was on tour! I replaced it with a replacement neck and put the old one on a shelf for 8 years. After time I checked it and it appeared to be good so I took off the fingerboard and put a Macassar ebony fretless one on and it’s been fine. I concluded that it had not been correctly prepared/dried before assembly. Good luck.

Edited October 13, 2021 by mybass

[3below]

2 hours ago, Hellzero said:

....And you can set up your truss rod at the strings tension, there's no need to slack the strings before doing that as it will modify the overall neck tension and getting the issues you mention.

 

Whilst this worked just fine for every other bass (of the far too many) that I have owned it produced catastrophic results with my USA G&L L1505 which gave symptoms like yours, the truss rod adjustments had little or no lasting effect.

 

2 hours ago, Stub Mandrel said:

I realised the end ancor of the rod was moving, crushing the wood.

 

The effect was as described by @Stub Mandrelwith the adjuster nut crushing the anchor wood.  The fingerboard eventually parted company from the neck and cracked.  A resultant trip to Jon Shuker for a new fingerboard and dual action truss rod. Better than new now.   I was also advised to slacken the strings when adjusting the truss rod.

 

@Hellzerosuggestion of grease on the truss rod nut is worth pursuing.  Another one of my basses had a tight truss rod, oiling the threads and adjuster helped.  

 

Might be worth looking at the StewMac Fender truss rod videos on YouTube? 

Edited October 12, 2021 by 3below

[Hellzero]

2 hours ago, NancyJohnson said:

 

While I'd concur with this, I feel the advice is more of a cautionary thing; the approach of leaving to let it settle should perhaps be more a case of allowing the neck material/glues/finish etc to settle.  While it's unlikely you'll experience failure, truss rod adjustment should be little and not very often rather than lots once in a whwile,

I understand totally the cautionary attitude, but after having set up really thousands of instruments, I never had a single problem with even two complete turns of the nut of a truss rod (tensioning it, not releasing the tension, of course).

 

But, as there's always a but, I always sense the pressure and tension when doing this. If it becomes hard or starts making weird noises, I always stop and if it's a single action truss rod, before any attempt, I always put some graphite grease on the thread.

 

That said, I've seen a luthier breaking a trussrod before my eyes by applying too much strength when it became harder to turn. Sh*t happens.

 

In fact the truss rod almost always breaks at the thread, which is the most fragile place.

[Ricky 4000]

15 hours ago, Welshbassist said:

I've gone through four quarter turns over the last few days and the nut is now getting tough to turn to the point I'm a bit uneasy as I don't want to muscle it and damage anything.

 

From what you say, IMHE, I'd back off the tension on the TR, and start again by experimenting setting it up with lighter tension strings - to ascertain whether the TR is doing what it should, without having to muscle it. Then report back. 🙂

 

 

[3below]

1 hour ago, Ricky 4000 said:

 

From what you say, IMHE, I'd back off the tension on the TR, and start again by experimenting setting it up with lighter tension strings - to ascertain whether the TR is doing what it should, without having to muscle it. Then report back. 🙂

 

 

This seems to be a very good plan . 

[jonno1981]

As a further option would you reconsider your string choice? I love the low tension of TI flats on my jazz. Not the cheapest by any means and possibly not what you’re after tone/feel wise but I thought I’d suggest it. 

[Welshbassist]

Thanks for all the suggestions everyone - plenty to think about. As some have alluded to here my worry is that something is up at the anchor and and I'm compressing the wood. I really like this bass so am not opposed to forking out for having proper work done on the neck - I'd just rather avoid it.

For now I think I'll take of the heavy strings and just see if i can adjust it using my old roundwounds just to see if the truss rod actually works. Will get some graphite grease and maybe try a clamp as suggested in the stewmac vid. Think I'll try and get try and get a closer look at the threads too and see if I can clean them up if needed. Will report back

[Welshbassist]

22 hours ago, jonno1981 said:

As a further option would you reconsider your string choice? I love the low tension of TI flats on my jazz. Not the cheapest by any means and possibly not what you’re after tone/feel wise but I thought I’d suggest it. 

Not opposed to this at all! I've head loads of good things about the TI's and tbh having flats that don't feel like steel beams sound quite appealing. Think I'd just rather be in the position of making that decision out of choice and have a sense that everything is functioning as it should.

[jonno1981]

I hope you find a solution! I tried loads of different brands of flats (not the cheapest experiment!) at 45-105 and really struggled  with lots of them due to tension. Rotos, la bellas had ultra high tension compared to roundwounds at the same gauge. I’d have to drop a gauge to make them playable for me. Best I found were daddarrio chromes 40-100, sadowsky flats (wonderful but where to buy from) and then I discovered the TI’s. About the same tension as the rounds I was used to, feel and sound amazing and last a very long time. 

[3below]

11 minutes ago, jonno1981 said:

I hope you find a solution! I tried loads of different brands of flats (not the cheapest experiment!) at 45-105 and really struggled  with lots of them due to tension. Rotos, la bellas had ultra high tension compared to roundwounds at the same gauge. I’d have to drop a gauge to make them playable for me. Best I found were daddarrio chromes 40-100, sadowsky flats (wonderful but where to buy from) and then I discovered the TI’s. About the same tension as the rounds I was used to, feel and sound amazing and last a very long time. 

My first set of TIs went on my G&L SB-1 in 2011 (from memory) and are still fine despite many hours playing and gigs. They are my first choice strings for the majority of my basses.  However, they do not suit some basses in my possession, e.g.  Labella 760FL (low tension, but a bit more than TIs) work better on one of my fretless basses.

Edited October 18, 2021 by 3below

[Stub Mandrel]

The advantage of flats is they sound craP  but don't get any crapper. And they feelovely to play.