Seasonal truss rod adjustment
 

The truss rod adjustment affects neck relief, which is a measure of the amount of bow in the neck.
It is not used to adjust action height, although an adjustment of the truss rod will affect action height.

Once the bass has been set up, certain things are not normally going to change by themselves. The
saddles should not move, the angle of the neck where it is set into the body is not going to change,
the string tension is not going to change. But when the strings start buzzing with a change in humidity,
something certainly has changed. The neck has bowed back, reducing the relief and also the action
height. Since the only thing that has changed is the neck bow, adjusting the truss rod should be all
that is needed to restore the bass to exactly where it was.

Again, the truss rod is not an action adjustment. However, if the only thing that has changed is the
neck bow, then the action height is a very good indicator of the amount of relief. If you know what
the action height was before the neck changed, you can set it back there very accurately by looking
at the action height.

This might be the best reason for using a 1/64th scale for measuring the string height. After the bass
is set up and you have an action you like, measure the action height. Whenever you notice a difference
due to seasonal changes, adjust the truss rod to restore the action height. Don't worry about relief
measurements if the relief was already set correctly originally.
If you prefer setting action by feel instead of measurement, then the procedure is still the same; adjust
the truss rod for the same original setup feel, instead of the same measurement. Not as precise, but
should still get things close.
If you prefer very low action and a dead straight neck, you should also be able to get close by adjusting
the truss rod to restore the action height. But a dead straight neck is critical; good to check actual neck
relief also in that case.

And when the action does change with the weather, don't simply adjust the saddles!
for all the reasons above. The saddles haven't moved; the neck did. You need to restore the relief.

Ehm, to whom are you speaking?

True, no one actually asked.
But just in case anyone was wondering

Bucking for a sticky hmmm? Lol

Maybe subconsciously?

Now that you mention it, post generally are questions, aren't they?

I must admit I found myself here hoping to help,but I see you got it covered..uhh,Good work!

So possibly I asked and answered myself?
Maybe a new topic format?

Also that should have been "...new topics generally are questions..."

LOL! Let me see..you're talking to yourself,stating your questions,questioning your statements,and correcting and reprimanding yourself along the way..How long have you been married? :D

It'll never fly. Dare to dream though.

Laugh all you want, but megafiddle has answered a question that I've had every spring
and fall.

I like this guy haha.

Yes, the same question comes up regularly here and is answered regularly here. All I'm saying is that soon this thread will begin moving ever closer to the bottom of the pile of threads and people won't search, because they may have another question to add and don't want to be 'that' guy to zombie a thread. So they'll start a new thread.

Hey I'm not laughing at you, I'm bumping the thread. ;)

Edit: good explanation you gave, copy it to a note on your desktop and paste it whenever it comes up so you don't have to rewrite it. 8)

All this post needs is this sentence at the beginning:

I've learned some helpful things about truss rod adjustments and thought I would share with the TB community.

Thanks to all, that was both helpful and humorous.

Have saved a copy for future postings when the subject comes up.
Good suggestion.
I guess a simple new topic like that isn't going to do much good after
it sinks into oblivion, either. Hadn't thought of that.

Adding an explanation of why it was there would have helped.
Another good suggestion.

This. Lol.

Actually, I've got a puzzlement y'all can help me with.

I'm experienced at doing my own setups, and understand what all the adjustments do. Not braggin', but other players are complimentary about the way my basses feel. Just saying that I'm not a noob at setups.

But what I've never quite understood is exactly what it is, when the seasons change, that affects the neck relief. OK, temp and humidity trend differently--but how does that affect the bow of the neck?


Edit: I'm thinking the neck relief is the result of the opposing forces of the string tension and the truss rod tension. That's why I'm not intuiting what weather has to do with it.

Wood shrinks when it dries out.

Seasonal changes are due mostly to humidity since we keep our basses indoors. But taking it from air conditioned room to an outdoor festival in the blazing heat will change the neck. Touring pro musicians that can afford techs have them to check set up on a daily basis.

Like 96tbird said,but for the long version..The pores in the grain contract as moisture evaporates. Wood also expands and contracts with temperature fluctuations. Up north during the winter months you get a double whammy due to the colder weather and all the ambient humidity turning to ice/snow. These weather conditions play on your neck because they ever so slightly change the mass and density of the wood it's made from. Combine those slight changes with the pressures exerted by the truss rod and strings adjusted in a warmer,more humid climate and it becomes readily noticeable..

I've heard people say this for decades and never agreed with the first part... because of what you said at the end of the same sentence.
:D

it most definitely can and is used to adjust action... because it does change the string height in relation to the fingerboard. And since everyone doesn't like the exact same relief, changing that relief while affecting string height can achieve the desired action.

IME once I've adjusted the saddles I rarely need to touch them again. And if someone is playing my bass and needs the action higher I'll typically adjust the trussrod... it's quicker than adjusting 4-6 saddles and much quicker and easier to reverse.
:cool:

Ah! Thank you and 96tbird for bursting open the lid on my understanding!

I was just considering the metal parts of the structure, the opposing forces of the string tension and the truss rod adjustment. But I get what you're saying--the truss rod sits in a wooden channel, and dimensional changes in that part plus changes in its rigidity would also affect the equilibrium point of the strings and rod.