Mysterious Truss Rod Shim

[frank falbo]

So I'm making a neck from some birdseye maple and I thought it would be nice to just steal the truss rod from an Ibanez neck I got that was destroyed beyond repair, complete with bad glue job and everything. The rod is like brand new. So I take it out, and there's the legendary shim between the two rods, right around the center. I've seen them before during truss rod replacements, but the new rods I was replacing them with never required them. They were always sheathed in tubing or plastic wrapping.

I remember hearing that the shim was either to avoid rattling or to apply some slight bow to the neck when at rest. Does anyone remember what those are for? I can't fit it into a perfectly sized slot because then the middle protrudes a little. I should know this, but for some reason I'm drawing a blank. If I don't remove the shim, I have to deepen the slot. Then I don't get the perfect fit I worked for. If I remove it, maybe it will buzz in there, I don't know. But I could eliminate the buzz with something thinner, like tape. This shim is thicker, like .5mm or so, and it was tack welded in place. Is this ringing a bell with any of you guys?

[thedoctor]

Yep. The shim is to keep the rod from tightening with the static rod bowed inward(towards the dynamic rod). As for buzz, a dab of silicone caulk every 4" will take care of it. Grind the shim to any width you need or take it off(probly difficult). If you are going to take it off and are paranoid, replace it with a piece of plastic cut to about the same thickness. Now, just don't put it in upside down(OH YES i HAVE).

[frank falbo]

Thanks, I examined another rod that I took from an Ibanez that I won't be using. The neck was waterlogged and the truss rod is rusted out. But there was no shim in that one. Both were Wizards but the no-shim one was an early one, like 1987/88 and the shimmed one was from '97 or so.

When you say upside down are you saying you've installed the whole rod upside down?

I can probably knock the shim clean off, it seems to be only tacked on. My main concern is that I like when the flat rod on top is in full contact with the board. If I relieved the slot another 1/64th to accomodate the shimmed rod, I'd only have contact in the pressure zones. Which seems to be part of most factory guitars' problems. They have extreme "hot zones" in truss rod activity. It's like they're giving the fretboard a kidney punch in one spot rather than smooth, even pressure.

Factories do a lot of things we one-off builders don't have to do, because we can work with tighter tolerances. Maybe this is one of them, but to recap, does anyone see a potential problem removing this shim, and replacing it with a longer piece of electrical tape for example, to eliminate rattle?

[thedoctor]

Yes, he says sheepishly, upside down. I thought the cool square part was supposed to make "complete contact" with the neck. What was meant was the fingerboard. I assumed it would adjust in compression as well as tension and I put it in upside down. The only saving grace in this was it could be removed and turned over cause of the head angle. If it had been a true straight-headstock Fender, it would be heat and cuss big time. Still cussed. Silicone caulk has it some strength even in little dabs.

I reccomend silicon caulk between the rods in little dabs to take care of the rattle/buzz. Assemble right after putting it on.

Edited February 8, 2005 by thedoctor