Why does the action raise

[smooth55]

This is a stupid question, but I'd like to know the science behind it. It seems that for all my guitars, even my JS1200 I purchased from Rich, have a tendency for their action raise over time. I'm sure it relates to weather and natural tension forces on the wood from the strings and springs. Still, I'd like to know why it is that every time I change my strings, the action seems to raise and I wind up having set things up a little. It's always to lower the action, never raising it.

[Rich]

If it's trem angle, fresh steel is always larger diameter than old played out steel. You may start at .009 but when you change it it's probably more like .0086. Neck relief is another point that will change action drastically.

[smooth55]

The trem angle seems to be level, and I've messed with the neck relief quite a bit, trying different things out and such. With my JS, the strings are the same type as what you installed but I still haven't ever been able to get it back to the way it was when I first got it. I guess I just have to keep messing with things to develop better skills
As for my original question, I guess I'd like to know if there was ever a situation that would cause the action to lower, despite the tension of the strings that typically force it to raise.

[rob777vdy]

good question.ive noticed same thing,i recently changed strings.before i changed strings the action was low and all level.ok so i stretch out the new strings a leave the guitar for a day or 2.now today i went to tune up and notice the action is quite high 12th fret onwards.has been very cold here last few days,might be that ????

[AxeHappy]

I've had to raise the action on guitar that I setup perfectly (for me anyways).

Temperature and humidity changes will effect your guitar. Wood contracts and expands blah, blah, blah. Typically it's not enough to notice really but I was keeping my guitar near a window at the time and it changed from winter to summer rather abrutly and blammo. Buzzing all over the place.

[Rachmaninoff]

Originally Posted by Rich

If it's trem angle, fresh steel is always larger diameter than old played out steel. You may start at .009 but when you change it it's probably more like .0086.

Good point, Rich!