American Strat Bi-Flex truss rod issue

[Evan Williams]

I've got a 2002 American Strat on my bench with a bi-flex truss rod issue. With the truss rod nut turned as far clockwise as I can take it, there is still 0.026" relief at the 9th and 10th frets. When strung up to pitch (with a 0.011" to 0.050" string set), the relief jumps to 0.050".

The nut was just about stripped when I got it (and, unfortunately, I may well have made that slightly worse), but it does still turn. I've also tried Dan Erlewine's recommendation of filing a taper on an slightly larger hex key to see if that can get a better bite on the nut, but the nut still cannot be turned enough to get a straight neck (or even less relief than I mentioned above). It just hits a clear stopping point. This is so even when I used blocks and a clamp to put a very slight convex back bow in the neck --- the truss rod nut simply does not go any further.

I'd be grateful for any advice on sorting out this problem, which, I understand, is not unheard of with these bi-flex truss rods.

Thanks.

--- Evan

[Mike Kolb]

Sounds familiar. You may have a different set of physics going-on, but my only fix for one in the shop turned out to be a simple washer.

The truss rod nut was bottoming-out (basically, running-out of thread before getting the rod to where it needed to be) so I removed the nut, placed a fat (1/8" or so) washer over the rod and reinserted the nut. The nut now had further to go before it ran out of thread, which tightened the rod and straightened the neck.

If you try this, don't give up on the block and clamps, as anything that helps the rod along is a blessing. Good luck.

[Evan Williams]

HI Mike,

Thanks for your response. How did you get the nut out? As I understand this bi-flex rod, the nut has washers either both ends of it, and the whole thing is sealed in by that walnut plug with a hole for hex key access. Perhaps my understanding is wrong. Did you have to drill out the walnut plug? I can see that if you put another thick washer on the inside, you can gain more turns for the thickness of the washer.

How did you do it? Thanks again for your thoughts on this; I really appreciate them.

--- Evan

[Mike Kolb]

Hi Evan...

OK, now I've gotta do the old "backstep shuffle". It was a Fender for sure, and a Strat.... well, maybe. This was about 3yrs ago and the guitar arrived and left the bench in a day. I apologize for not having a clearer memory of the guitar itself. {note to self: start and keep a detailed diary of repairs}

So having said all of that (and addressing your specific guitar) it's either drill-out the walnut plug or access from the top via removing the fingerboard... neither of which sounds like much fun but the plug route might be easier. And while I'm clarifying things, the washer itself was probably closer to a 3/32" in thickness, but it was enough to gain an additional 360° of turn, which is all it took.

You mentioned using the blocks to put a very slight convex back bow in the neck.... maybe something over 'very slight' would be helpful, like maybe a good 1/4" or more flexed down at the head. Your gut & ears will tell you how much you can get away with...(but don't sue me if if breaks!) As you said, though, if you're hitting a definite stopping point, as opposed to "it's getting tougher and I don't wanna break it" point, then it sounds like you're running out of thread and should try to get a spacing washer in there somehow.

Keep us up to date, since (as you mentioned) it's not an uncommon issue.

[Evan Williams]

Hi Mike (and all those interested in this issue),

I offer my apology for taking so long to get back (it's a case of the day job getting in the way!).

However, I've had a chance to do a bit of research, and have found some interesting and useful information. For brevity's sake, I won't repeat it all, here; but please check out the links, given below.

First, check out the following link from the Telecaster.com forum for a pretty good description of how this Fender bi-flex truss rod works. It is a unique design. Note that in the first post by "jwells393", he has a link to an image of Fender's blueprint for the American Strat neck that includes some detail about the bi-flex truss rod.

http://www.tdpri.com/forum/telecaster-discussion-forum/95999-truss-...

More useful discussion from the same forum can be found at:

http://www.tdpri.com/forum/tele-tech/109142-truss-rod-problem.html

There is another extremely informative discussion at:

http://www.fenderforum.com/forum.html?db=&topic_number=692221&a...

Scroll down to the first "strayedstrater" post; he provides a pretty well-rounded account of the various potential problems with the bi-flex truss rod, their causes, and the various solutions --- including the possibility of getting a replacement neck through Fender's "lifetime warranty".

I think with the Strat that I am looking at, the nut has run out of thread, whether it's due to wood compression or something else. The warranty route is probably not an option. So I suspect that I will bite the bullet and ream out the walnut plug to extract the nut. If the hex slot is stripped beyond use, I'll get an new nut. Otherwise I'll just add a thick spacing washer to the system to give another clockwise turn or two of adjustment for counter-acting the concave bend that this neck seems to have.

With this neck, adjustment the other way (the reason behind the "bi-flex") is not needed; but, in the name of keeping the neck as "stock" as possible, I'll return that function to the neck (if possible) with an appropriately-size new walnut plug. Fun times ahead!

Thanks again for your thoughts, Mike.

--- Evan