I am pretty sure this rim is shot, but wanted confirmation and/or a better understanding of what's up. I'm fixing up a donor bike that was pretty apparently stored outside for years. Despite that, many of the parts are salvageable -- so good in fact that I decided to just overhaul the bike rather than part it.
Except the wheels? Rear wheel was pretty badly out of true. So I put it in my stand, tested the spoke tension, it was all over the place on the drive side, from 80-140 kgf. Non-drive similar, but not such high tensions. I began backing off the spokes and trying to get drive side to about 105 kgf, non-drive about 65, and the thing got worse.
I backed off all the spokes until they were slack. The rim (a 23mm wide, 32-spoke aluminum with plenty of brake track, BTW) looked fairly straight. I had expected it to show evidence of being badly bent, but it looked no worse than plenty of wheels I've gotten nice and straight.
So, I began tightening again, moving up slowly. Probably 5-10 kgf per side. (It was tedious.) As soon as I got the drive side up to about 55 kgf (non drive would be about 17 at this point I guess) The thing started to pringle badly again. That's with tensions nearly perfectly even on each side. The rim's easily 1cm out of true.
I'm convinced this thing is a goner (not surprised given its history) but I've never seen a rim behave like this. Maybe all that weathering and corrosion has just made it completely and randomly unstable? I was thinking maybe the eyelets were failing in some spots, but of course, if I had eyelets failing or weak spots near holes, I'd see the move reflected on the tension. I don't. I get even tension and a really warped rim.
Anyone seen this on an old rim?