Can old strings screw up the intonation?

[NoiseNinja]

As the tittle says, can old roundwound strings mess up the intonation?

[Nev375]

Yes and no.

If your bass was intonated to a particular gauge/set of strings, you can put a fresh set of those on and your intonation will be accurate. So no, nothing is "messed-up"

However, strings do not stretch uniformly so they are often difficult to intonate as they get old. So yes, you will probably have to re-intonate to your old strings, and again to new ones when you replace them.

[rodl2005]

I ain't an expert but I know they can go outta tune ready easy, &I s'pose with rust & gunk build up they could make intonation go out.

Use the denatured alcohol method & clean em b4 they get that bad

[fretlessguy]

It is good to intonate periodically due to changing of the seasons and other factors.

[JTE]

Intonation assumes the strings vibrate consistently along the whole string and have consistent mass along the fretting portion. Old strings get dirt and crud in them and don't vibrate true.

John

[knuckle_head]

Identical gauges from the same manufacturer will intonate differently as there is no perfect wire or winding process - consistent perhaps but not perfect.

Age or new/used will have little to do with it. The intonation point will shift with each new string across your saddle at least a little.