Double Truss Rod Question

[Budha]

I have a new-to-me 1990 JF30-12 with double truss rods. I have never owned a Guild guitar nor a guitar with double truss rods. The neck relief needs to be adjusted. There is less than minimum relief. My understanding is both truss rods should be adjusted equally. Right now the bass side truss rod nut is one full turn tighter than the treble side. Should both truss rod nuts show equal amounts of tread above the truss rod nut.

Additional information: right now the treble side relief is less than the bass side relief, yet the bass side truss rod nut is run down tighter than the treble side.

I feel certain the saddle has been shaved in the past because string height in front of the bridge is 0.4".

I am not certain where I should go with here considering the current position of the two truss rod nuts. Should the two truss rod nuts be tightened equally when counting the number of threads exposed above the truss rod nut? In the past I have handled my own setups on Martins but perhaps its time to take to a professional.

 

[DThomasC]

I know nothing about double truss rods, but I would not use the number of exposed threads as an indicator of tightness. I think that's a total red herring.

 

[Nuuska]

Hello

Like DThomasC says - do not count visible threads - see how the side of each truss rod is and act accordingly. They both affect mostly their respective sides, but naturally they affect each other - being so close. And remember not to strip the threads by force tightening. My method is to put the guitar standing between my knees while I sit on a chair - then I pull the neck back with my left hand to release tension on truss rod - then I adjust and see what I got - repeat when needed. Also remember, that neck might be stiff enough not to react immediately - so take your time.

 

[GardMan]

There is less than minimum relief.

This suggests to me that there is TOO LITTLE relief, which means you should be LOOSENING the truss rods, so that string tension can pull more relief into the neck..

I have no experience with a dual truss rod neck, but my first move would be to loosen both rods an equal amount (1-6 to 1/4 turn), and see what effect that has. Once the bass-side relief is where I wanted it, you could then try adjusting just the treble-side rod to bring it where you want it (you might have to readjust the bass side after working on the treble).

 

[Quantum Strummer]

My approach with various dual-trussrod Rickenbackers is to adjust both rods by the same amount, then check the relief on both the first and last (pair of) strings. That is, both Es if you're in standard tuning. Then tweak tiny amounts if necessary. If you're dealing with a guitar whose rods are "out of sync" with each other, you may have to do a series of tiny tweaks to one or both rods to get the relief right on both sides of the fretboard. Take it slow.

-Dave-

 

[Budha]

I used a 1/4" nut driver to get a feel for the difference in torque currently applied to the two different truss rod nuts. I lubricated the nuts a few days ago to make sure they will move easily. The bass has much more torque (based on feel) currently applied than the treble side. The bass side is one full thread showing above the truss rod nut as opposed to the treble side nut. I plan to very-very slowly, over the course of at least a week, balance the torque on both truss rod nuts with an end target of a neck relief of approximately 0.006". Yesterday I backed off the bass side 1/8 turn. Today I tightened the treble side 1/8 turn. I'll report back on how this learning adventure goes.

 

[DThomasC]

I don't have experience with double truss rods, but I do have experience truing bicycle wheels. There you don't worry so much about making the tension on each spoke equal but instead worry about making the wheel straight and true. My advice is to worry less about the current relative difference between the two truss rods and instead worry about making the neck into the shape that you want it to be.

 

[DThomasC]

I suppose one approach that might satisfy you is to loosen both truss rods completely, give the neck a day to adjust (I don't think it should take more than that) and then start over from the beginning as described by Quantum Strummer. But I really think your goal of making both truss rods have the same tension is misguided.

 

[Budha]

DTC, I appreciate your thoughts on this. The bass side being so much tighter than the treble side concerns me. I feel my plan fairly closely follows Quantum Strummers ideas.

 

[Budha]

I have the torque balanced on both nuts after 5 days of slow adjustment. The relief is approx. 0.006" on both sides with the torque balanced. I measured relief several times a day as the guitar settled after making the rod torque balancing adjustments. Some folks had indicated they thought treble side truss rod adjustments had more effect on the treble side of the neck (same for the bass side and bass truss rod). I did not observe any direct correlation between treble rod to treble side of the neck nor the bass rod and the bass side of the neck. The two rods seemed to work together as a unit.

 

[Tom O]

Check a string tension chart for the gauge strings you are using. The bass strings may have slightly higher tension. If there is too much difference in the truss rod tension, you may induce a twist in the neck over time. Keep experimenting with small changes.

 

[kakerlak]

I don't know how much of this translates in practice, but, in theory, the double rods are there precisely to allow one to be adjusted to a higher tension than the other. I think, theoretically, that the tension load on a 12-string is probably skewed towards the bass side and the neck might want more tension on that side's truss rod to counter the twisting force.