Bob Ross

There is one spoke -- and only one spoke -- on my rear wheel that has started coming loose after only a handful of rides (been less than 200 miles since the last time).

Wheel is handbuilt by a local wrench from DT Swiss components: RR465 rim, RR1450 hubs (same as 240s), 28-spokes 3-cross. I did ding the hell out of that rim on a huge pothole ~3 months ago and that same wrench did a wonderful job of hammering out the dent. That was about 2,000 miles ago. Then three weeks ago I was on a ride and heard the tell-tale "ping" of a loose spoke. Tightened it up, continued riding

...and yesterday I hear the same sound. Sure enough, it's the exact same spoke. Drive side, 4 away from the valve stem. And nowhere near that old dent, in case that matters.

Any idea why the same spoke -- and only that one spoke -- might continually be coming loose from JRA?

Thanks.

AnkleWork

Maybe not tightened enough?
Is twice "continually"?

Airburst

Last time I saw anything like that it happened to me. In my case it was because I'd either gotten a dodgy spoke nipple or damaged the threads in one by cross-threading it onto a spoke while lacing the wheel - either way the "ping" was the spoke pulling through the threads. There was enough metal left to wind it back up to a reasonable tension the first time it happened, but the second time it wouldn't pull tight at all. Luckily I spotted the issue test-riding the bike around the shop, as it wasn't my wheel!

The timescale between the failures makes that a bit unlikely though...

Bill Kapaun

One could make multiple guesses as to why-
Maybe when your 'wrench" rebent the rim, he ended up having to use uneven spoke tensions to get it true.
I'd probably install a new nipple and see if that fixed it.
It probably won't, so the next step would be to use a thread locker such as linseed oil or Blue Lok Tite.
OR take the wheel back to the wrench and let him deal with it. He has the best insight.

FBinNY 

Obvioudly seeing the wheel would help, but it's fair to assume that, after a major dent removal and alignment, all spokes aren't working equally hard. It's possible that this spoke cannot be brought to high enough tension to not zero out under load without pulling the rim out of true. Losw spoke wheels need higher tension because the rim has more flex in the longer spans between spokes.

It's also possible that something is happening to the rim, like stress cracking near that spoke so it's slowly giving way.

Either way, I'd either let the person who saved it before take a look, or try using something that to bind the nipple. I prefer not bonding the spoke and nipple, and would use some adhesive between the nipple and rim. You can buy a wickable grade of Loctite, or go cheap with a nylon based nail polish, or some kind of glue. Fix the wheel, then apply a drop between the nipple and rim and spin it in.