What would happen if i change my string's from 9's to 10's? I'm pretty sure the action will get messed up, but will anything else happen? I've used 9's on this guitar for about a year now...
it will change the intonation. espically if you have a floyd rose or whammy bar of some sort. you you will either have to raise or lower the action.
Ok, i can fix the intonation, but i've never really tampered with the action before, because it was exactly where i wanted it when i got it stock... Is it very hard to fix the action for your first time?
The action shouldn't change, the intonation might.

Action is determined by how high the strings are off the frets. This is measured at the bottom of the strings. I set mine about 1/8" at the octave, if I switch to .010 they will still be 1/8", just a bit stiffer. That means it will be a llittle harder to fret the notes no matter where the action is set, and a little harder to bend strings. But the string height won't change.

Intonation might change, it depends on the guitar. Some change signifigantly, some only a little. I switched to light top heavy bottom strings on a Les Paul copy years ago and had to get a wide throw bridge for it because it didn't have anough saddle adjustment to set the intonation with the standard bridge. Other guitars I only have to fine tune them a little. When I went from .010 to .009 on my Peavey Patriot it was so close I only had to change the 3 wound strings a tiny bit. Maybe a full turn of the screw, that's not much.

Put the strings on and check it, the action will be a little stiffer and the intonation might be off a little, but you probably won't have to tweak the action much if at all, the string height will still be the same, you'll just be using stiffer strings. If you lower the action they will still be just as stiff, you just won't have to push the strings down as far to fret a note. If it's a standard tune o matic bridge, tweaking the action isn't hard, but recheck the intonation after making any adjustments. Changing the action might also change intonation.
Hmmm...I wonder what this button does...
Quote by Paleo Pete
The action shouldn't change

It will, albeit slightly. The increased tension will bow the neck more, causing the string height at the higher frets to increase. This can be solved be tightening the truss rod slightly.

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