Are shims bad?

[ChrisDesign]

Do well-fitted shims have any disadvantage? I have a whole-pocket maple shim in my Jazzmaster, yet I'm wondering if there is any negatives?

[bodhi]

No, not really. The ones that don't fit the full pocket might actually cause issues with the neck and fretboard over time, and you can find horror stories of these online, but ones that cover the full surface don't have meaningful negatives from what I gather.

[Lost In Autumn]

Only positives: lower action, steeper break angle, increased tuning stability and reduced buzz.

[timtam]

Assuming your guitar needs a shim, then I would say no real negatives, as far as full-pocket shims are concerned.

Reasons for shims (positive or negative taper):
To retrieve adjustment range on a bridge that has reached the top or bottom of its range and you still can't get the action you want.
To achieve higher or lower downforce on the bridge, when it needs that.

If you add a shim for the wrong reason, that can obviously be counter-productive.

There is no evidence I know of that a full-pocket shim has any sonic effect (nor incidentally that a narrow one does either .. although there is more reason for suspicion there).

Regarding narrow shims (ie not full-pocket) there is a school of thought that over years, the shim can distort the end of the neck, since only part of it is fully supported. Gerry Hayes is one luthier who believes narrow shims can lead to 'ski jumps' and so are best avoided ...
https://hazeguitars.com/blog/neck-shimm ... t-research
https://hazeguitars.com/blog/ski-jumps- ... n-language
He does show some pics of necks which such issues. But there is the concern that, like with doctors, guitar repairers only see 'sick' guitars. No one is ever going to do a long-term study where they check not only guitars that turn up in repair shops with neck kinks, but also the many in the wild with narrow shims (often factory-installed historically by Fender) that may or may not have such problems. So we'll probably never know for sure.

A full consideration of shims would also include Fender's micro-tilt system - the original 3-bolt version and the more recent 4-bolt version. I think the notion of propping the neck heel on the end of a single bolt is such an extreme one that it requires very good proof that it is not a bad idea. I know of no such proof.

[JVG]

It seems crazy to think that a narrow shim can distort a neck. I mean, we’re talking about shifting about an inch thickness of hard maple.

I used to be a vocal sceptic until it gradually happened on two of my guitars, one quite subtly but the other more dramatically. As a result, i’m convinced it’s a real thing, although perhaps in the minority of cases.

Shims are awesome in terms of what they do for your setup, but as a result of personal experience i also support the full-pocket variety.

Cheers.

[jvin248]

.

Strip of business card as a shim is ok too.
paper/card stock is made of wood.... and you know because it floats like a duck.

https://www.youtube.com/watch?v=zrzMhU_4m-g

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[kgbAttack]

As I took my AVRI Jaguar to a luthier who was inexperienced with the overall design of the guitar, I was lead to believe that shims were going to affect the sound in negative ways. He'd replaced the stock, cardboard, shim with a full pocket shim made of wood and then actually angled my neck pocket a little and removed the shim altogether. The result was okay but as I learned to set up my guitars myself (with the precious help of this forum!) I have put back a StewMac shim on my Jag and added one to my Jazzmaster which didn't have any and got to a better string action and overall angle break. I like my bridges set up a little higher and to do that StewMac full pocket shims are relatively inexpensive and are easy to sand to fit in the neck pocket.

[krossfader]

I haven't had any issues with shimming my Jazzmaster. I think I need to get another for my Mustang.

This video from StewMac offers a good visual explanation of some potential reasons to shim:
https://youtu.be/kIUzd0IjchU

[ChrisDesign]

As I took my AVRI Jaguar to a luthier who was inexperienced with the overall design of the guitar, I was lead to believe that shims were going to affect the sound in negative ways. He'd replaced the stock, cardboard, shim with a full pocket shim made of wood and then actually angled my neck pocket a little and removed the shim altogether. The result was okay but as I learned to set up my guitars myself (with the precious help of this forum!) I have put back a StewMac shim on my Jag and added one to my Jazzmaster which didn't have any and got to a better string action and overall angle break. I like my bridges set up a little higher and to do that StewMac full pocket shims are relatively inexpensive and are easy to sand to fit in the neck pocket.

What degree shim did you use?

[jorri]

If they are then consider that you'd have terrible break angle and action.
it never outweighs it i guess, so who can know? Who is making a blind test where the guitar is returned to the same break angle and action? If a guitar is built with a correct break angle in the firsblt place perhaps id go for that over a shim because "why not?"

You can get warpage if its a very thick,but narrow shim on the heel. That could be an element, otherwise the whole resonance argument goes on....which doesnt necessarily have basis since to add to my last paragraph, less connection in pocket vs more connection at bridge where there is more tonal effect anyway. Not that it determines better sound, as i LIKE the sound of a low break angle hence play a JM.

[kgbAttack]

As I took my AVRI Jaguar to a luthier who was inexperienced with the overall design of the guitar, I was lead to believe that shims were going to affect the sound in negative ways. He'd replaced the stock, cardboard, shim with a full pocket shim made of wood and then actually angled my neck pocket a little and removed the shim altogether. The result was okay but as I learned to set up my guitars myself (with the precious help of this forum!) I have put back a StewMac shim on my Jag and added one to my Jazzmaster which didn't have any and got to a better string action and overall angle break. I like my bridges set up a little higher and to do that StewMac full pocket shims are relatively inexpensive and are easy to sand to fit in the neck pocket.

What degree shim did you use?

On the Jaguar and the JM I put a .25 deg shim. The Jaguar has a Mastery, which typically should stay low as the saddles have more angle. The JM was playing perfectly but had the action a little high for my taste, so I put the .25deg shim and raised the bridge just a touch.

On the Bass VI I instead put a 1deg shim, to further reduce the floppiness of the strings. On both the JM and the Bass VI I needed to adjust the truss rod to avoid fretting out around the 16-17th fret, where the neck touches the neck pocket.

[ChrisDesign]

I added a 0.5 degree shim. I wish I had bought a 0.25 degree.

How do you adjust the true rod to prevent 16th fret buzz?

[crianlarich]

Same question here.
My luthier told me that the full pocket shim was the remedy for that problem. Which has to do with tension from tightening the neck screws. So truss rod adjustment would be no use at all. Right or wrong?

[jorri]

I added a 0.5 degree shim. I wish I had bought a 0.25 degree.

How do you adjust the true rod to prevent 16th fret buzz?

You dont! A truss rod adjustment is more for lower frets.
You adjust action, the fret level, and maybe warpage of the heel but as you say a full pocket shim shouldnt do that logically.

[jorri]

I added a 0.5 degree shim. I wish I had bought a 0.25 degree.

How do you adjust the true rod to prevent 16th fret buzz?

You dont! A truss rod adjustment is more for lower frets.
You adjust action, the fret level, and maybe warpage of the heel but as you say a full pocket shim shouldnt do that logically.

Although id add straightening the neck when the lower frets are fine has sometimes allowed me to have a higher action without any extra feeling that its hard to play.