What causes rim failure where spokes pull it apart? I've seen a few failures like this lately from touring cycling groups, and I'm wondering what causes this kind of rim failure (if it can be generalized).



poster on group reported shortly after this that there were two other (three total) spots looking like this. Looks very distinct from the side blowouts caused by brake wear.

Is it just overtightened spokes?
If there are several spokes showing this failure, it's not because of a single impact.

I think it's safe to say that the rim was simply overloaded and has suffered metal fatigue from stress cycles imposed by the differing forces on the spoke as the  wheel rotates.

Can't say if the failure is because of overloading beyond what the wheel was designed for, or poor design or a manufacturing problem.