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Alembic Club » Alembic Basses & Guitars » Archive: 2003 » Archive through June 04, 2003 » Truss rod adjustment, did I do something wrong ? « Previous Next »

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Username: thebass

Post Number: 19
Registered: 3-2003
Posted on Monday, May 05, 2003 - 8:16 am:   Edit Post

I tried to adjust the dual truss rods on my MK STD and now I am curios if I just don't understand how they work or if I have a more serious problem.

If both truss rods are without any tension (both nuts fully counter clockwise until they are loose) the neck should have its maximum bend towards the strings, right ? Now when I looked down the neck (using 90-70-55-35 strings correctly tuned) no truss rod tension at all, the necks bow towards the strings is much less under the G string than under the E string. Even more underneath the G string there was only very little (almost no) neck bow towards the strings. Assuming that the dual truss rod can compensate the string tension either half of the neck seperately I fastened the left truss rod (underneath the E and A string) to compensate the unequal bow. But I was only partially able to compensate the uneven string tension (froma certain point the left truss rod also bends the right neck side) and could not adjust the neck down to my preferred low action without a string buzz.

My question is did I understand something wrong how the dual truss rod work or do I need to worry about a neck warp ?
Intermediate Member
Username: elzie

Post Number: 111
Registered: 8-2002
Posted on Monday, May 05, 2003 - 9:19 am:   Edit Post

Here is a good article to read. The better you understand it, the better prepared you will be. This is an easy to understand, yet informative tutorial for truss rod adjustment.

I hope this helps you!

Paul II
Username: bob

Post Number: 40
Registered: 11-2002
Posted on Monday, May 05, 2003 - 5:34 pm:   Edit Post


It sounds to me like your understanding of the truss rods is pretty good. From other posts here (you might try searching), Alembic normally recommends that you adjust the two rods equally, though it's fine to do one a little more than the other if you need to compensate for small differences. As you discovered, you can only go so far on one of them before it starts affecting the rest of the neck.

It's hard to say how much twist or warp is excessive. You might want to measure the difference between the two sides to give us a better idea.

Putting aside the twisting, it seems that some people run out of adjustment range, particularly if using lighter gauge (or lower tension) strings, or if their climate is much different than Santa Rosa. My guess is that Alembic prefers to build the instrument such that it does not require a huge amount of truss rod tension, so in some cases you get to where the nuts are loose but you wish you could loosen them further.

They can fix this, by giving the neck a heat treatment (I think) - if you're willing to send it to them. I haven't seen any suggestions on how to do this yourself, but perhaps Mica or Valentino will have some advice.
Intermediate Member
Username: bigredbass

Post Number: 105
Registered: 9-2002
Posted on Monday, May 05, 2003 - 11:42 pm:   Edit Post


My first question would be: Are you 'eyeballing' the adjustments ONLY, or are you using rulers, feeler guages, etc.?

From your description, I agree you 'get it' about the dual truss-rods. And I would doubt you need to worry about a neck warp or heat treatment.

Action is made up thousandths of an inch here and there: The depth of the nut slots, the spacing of the frets, the bridge placement, the string heights, etc. AND the amount of bow (or, relief) in the neck.

Until I began to use a machinist's 6-inch ruler and feeler guages (the blade type, like we used to use for auto ignitions), my adjustments were 'eyeballed' and inconsistent.

My adjustment routine follows this method:

Tune to 440 (Remember, tuning is tension).

I check the heights at the nut, or more precisely the string clearance over the first fret. They should measure out like this:
G, .020"
D, .025"
A, .030"
E, .035"
B, .035"
This is measured with the feelers. If they needed adjusting, I loosened the nut lock screw, raised or lowered the pertaining half of the nut, then locked it back down when I finished.


Then I measure the string heights over last fret. I go for a 16th of an inch under the G, and 1/8 to 3/16" under the B, by raising or lowering the appropriate side of the bridge. As ALEMBICS use 1-piece bridges, this will induce a slant to mimic the nut heights. Generally you will always need a LITTLE more room on the bass side as the bass strings flop around in bigger arcs.


Now use a capo to fret the strings at the first fret. I hold the B-string down at the fret over the neck/body joining spot. I now get the feeler guages and find 12th fret. The string is a straight line between my right hand and the capo. I find out what the gap is now. I then adjust the truss rod until I get to a .010 or .012" gap at the twelfth fret.


Now turn the bass over like a left-hander and repeat this process with the G-string.


Now, I play with a VERY low action and a light touch. If you prefer a higher action, experiment until you find numbers that suit you. Now you see why I can't eyeball adjustments this fine.

The short version for the less technically-inclined who prefer a higher action is:

TUNE to 440.
FRET each string at the third fret: Raise or lower the nut until you can hear the string just tap the first fret when you press it there while holding the note at the third fret.
RAISE the bridge on each side until there's a 1/8" clearance under the G and B (or E).
ADJUST the truss rod tension until a Fender thin pick will just fit between the string and 12th fret while capoed and held as above.

Measuring the relief on each side will allow you to essentially adjust the two truss rods separately, yet identically. This should eliminate any twist. You would SEE the twist in the measurements. On my five-string, the B-side always takes more time, because there is obviously more tension from the E and B, than the G and D.

Two reminders:

After you do this, you may have to 'chase' the neck relief (a few slight turns on the rods) for a few days until the wood takes its final set.

You would need to repeat this if you install a different set of strings than the set that is on at the time you do this. ALL of these are slight turns on the truss rods: A 1/4 turn is a LOT. And try to do the truss rods like your tuning keys: Always tighten UP to where you want it, not loosen DOWN to it; this will 'set' things at tension.

Remember that there is a delicious interplay of tension, heights, and relief. Don't be surprised if this takes quite a while the first time you do this: Over time, you'll become quite good at it, and wonder why you didn't learn this earlier.

Plus, do you really want STRANGERS working on your MK? Horrors!

J o e y

PS Not enough range on the truss rod? Add flat washers under the nut ONE AT A TIME to get a little more leverage.
Senior Member
Username: palembic

Post Number: 405
Registered: 9-2002
Posted on Tuesday, May 06, 2003 - 12:52 am:   Edit Post

I knew it - I knew it.
Put Joey and Bob together on a thread and hup ...printing time!
Joey ...I really admire your way of explaining things.
I'd like this info earlier but (that old but of mine...) okay ...we're still learning.
And shure it takes a while ...and a while ...and a while.
Joey: what are those "Feeler Guages"??
"Feeler Gauges"? Where can you get them? What kind of store would have them over here on our side of the pond? What do you think Werner??

Mein freund Werner.
If I may add something.
Adjusting an Alembic is a very VERY precise job. It's a fact: it goes with 100th of a mm change and taking in account about 5 or 7 parameters.
You living in Germany and I in Belgium, we can fairly accepy us to be in the same "climate zone". My "Bonnie" needs adjustment at LEAST 4 times a year. If I want it more critical: 6 times. It's why I gave out the warning once in this club to new Alembic owners:
"BEWARE: IT'S ALIVE!!!!!!!!!!!!!!!!!!!!"
Or also:
" It will take some time the Alembic playing you before you play an Alembic".
Our lovely Mica once said thatr the best thing is to make Alembics and deliver them after 10 years to the customer. Simply because -although they breed beautiful instruments in Santa Rosa- they cannot convince the used trees that they are a guitar now.
For our climate: we have high "humidity" contrasts: a cold winter could be dry or wet. A hot summer could be dry or wet etc ... .
It takes time Brother Werner, and care!
It's good to be in the company of these fine people like Bob, Joey, MIchael, Dino, Steve, Val etc...etc ... who want to share experiences.
Thanks to you all!

Paul the-bad-one

PS: Werner, as you could see at my "author status" I recently became a "senior".
Please: don't be mislead. I'm as "freshman", only : I talk too much!

(Message edited by palembic on May 06, 2003)
Username: bob

Post Number: 41
Registered: 11-2002
Posted on Tuesday, May 06, 2003 - 1:08 am:   Edit Post


You've described this routine a few times before, but this is "clearly" the best one yet. Thanks - maybe I will dig out that old set of feeler gauges after all...

However, I'll take issue with your PS. From my reading, Werner got to the point where his nuts were loose (well, not his, but those on the truss rods) - and I think he was saying that his neck was still too flat, with not enough relief. Adding washers is not going to help in this case.

It's the opposite problem, that the neck wood itself already has more than sufficient back-bow to counteract the string tension. You could wait a day or two to see if it "relaxes" enough, but after that I'm pretty sure it's time for the sauna.
Senior Member
Username: palembic

Post Number: 406
Registered: 9-2002
Posted on Tuesday, May 06, 2003 - 1:16 am:   Edit Post

Cool ....we can take our Alembics at the sauna!

(Message edited by palembic on May 06, 2003)
Username: thebass

Post Number: 20
Registered: 3-2003
Posted on Tuesday, May 06, 2003 - 2:27 am:   Edit Post

Thanks to you all for your help, specially to Joey for his detailed description. As you correctly guessed I only used eyeballing (as always before) to adjust my bass. But it seems a good idea to me to start measuring instead of guessing. After translating the values to european measures (1"=25,4mm) I will go and get a set of feeler gauges like as used for adjusting motor valves. They start at 0.05 mm (approx 0.002") to 2.0 mm (0.08"). Then I will follow your procedure. I also noticed that the neck back-bow changes a bit over time (and probably because of humidity/temperature changes). If the neck back-bow is still too much after the procedure I may have to change to heavier strings but I don't like the feel and sound of heavier strings at all.

May be I can only play light strings in winter ;-)
Intermediate Member
Username: bigredbass

Post Number: 107
Registered: 9-2002
Posted on Tuesday, May 06, 2003 - 7:56 am:   Edit Post

The feeler guages are available at auto parts stores. Really good sets are also used by machinists, though these are very precise and more expensive.

All of this and more I learned in Dan Erlewine's excellent book, "The Guitar Player Repair Guide", published by GPI Books/Miller Freeman Books. I cannot recommend this book enough as an excellent primer/tutorial on any level of adjustment or repair you'd like to learn about. ISBN 0-87930-291-7. I'm sure it's available in the EU.

In my experience I've rarely seen a neck with a lot of 'up-bow' or convex relief on its own. I have seen this on instruments that had a loosened truss rod that was never snugged up for a proper set-up. In other words, the neck was stiff enough that a very little truss rod tension was enough to supply a 'just OK' action. Or it's the original factory set-up which has, over time, become a little loose as the neck set with the aging process. Either case is not uncommon.

Once the player decided he wanted to really get serious about his action, then it seemed like up-bow as the neck hadn't been tightened up long enough to 'change its mind' and take the new relief/ tension. After a few days, I bet it will come around. This is not uncommon. Or just as likely, the up-bow you thought you saw may not actually be there once it's measured. Believe me, one thing I found out learning and doing this is that you CAN'T always believe your eyes, because these are such tiny measurements.

Also, the way you talk about such changes with weather/humidity would make me think this is the case. Wood will move, but with the care that ALEMBIC exercises in its selection and construction, I would tend to think it's taken a slightly different relief due to shipment to Europe and the time since its completion. I'm sure just a little tweaking will stabilize it to your choice of strings. The laminations typically make these necks more stable than most. After that, as long as you avoid the obvious pitfalls (leaving the bass in a hot car trunk all day, etc.), you should be able to enjoy your bass with only a minimum of touch-up from time to time, as long as you stay with the same set of strings. And changing to different strings will require less work once this is done the first time.

As always, proceed slowly, make small adjustments, and listen to what the wood is telling you. I certainly want no one reading this to get in over your head and damage your instrument. If this work isn't for you, find a good, qualified guitar tech, pay him well, and enjoy the benefits of his experience and expertise.

J o e y
Username: davehouck

Post Number: 51
Registered: 5-2002
Posted on Tuesday, May 06, 2003 - 3:39 pm:   Edit Post

Paul asked what feeler gauges are. Here's an example:
Senior Member
Username: palembic

Post Number: 408
Registered: 9-2002
Posted on Wednesday, May 07, 2003 - 7:02 am:   Edit Post

Friends ...I'm off to a auto-parts store!
Thanks to you all.
I'm finished with this "eyeballing" (what a word...!!!) and into Feeler Gauges.
I put this procedure to the test this evening and will get back to you in a couple of days to rapport


PS: maybe I could start into motor-tuning too??LOL
Username: thebass

Post Number: 23
Registered: 3-2003
Posted on Friday, May 09, 2003 - 2:12 pm:   Edit Post

Just an update and a thank you all: after translating all the units to metric units (1 inch = 25.4 millimeter) and checking them with a feeler gauge I found that my setting is quite low compared to Joeys suggested values. The string action at the 1st fret ranges from 0.5mm (E) to 0.25mm (G). At the 24th fret I measured 1.8mm (E) and 1.2mm (G). After raising them to a more "reasonable" values the buzz disappeared. I still have the uneven neck bow underneath the G and E string but it does not disturb anymore and I guess it's a result of the thin string gauge I use. Since I will get the frets dressed by a luthier he may also find a lower setting.
Senior Member
Username: palembic

Post Number: 417
Registered: 9-2002
Posted on Saturday, May 10, 2003 - 1:02 am:   Edit Post

Brothers ...I've found "feeler gauges".
HA! The first step in "Paul's adventures with strings and neck-adjustment"
hey .... I'll make a thread out of that and make it a kinda "soap" . You all can monitor what I'm up to!

Paul the bad one who can check distance now!

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