Looks like it split right at the rim junction. Either pressure and/or heat likely accelerated that.

I don't know how this rim is made (if or if not there is a pin in place at the rim mating surface and/or weld). Doesn't look like a pin was there. How much pressure did you have on the wheel while on the trainer? Just curious.

110 psi. I was riding a Veloreality Lynx which has a large diameter (6"?) solid aluminum roller so I don't think heat was an issue.

Yeah I was just speculating.

Interesting trainer, hadn't seen that before. I'm not sure what else would cause this besides just general fatigue.

I haven't looked at Velocity Arrowheads in a while. They used to be pinned and machined. I think that's weaker than the welded and machined technique that I *think* Mavic perfected.

That said, I've never seen a pin or weld fail.

Even though they now look like they have machined braking surfaces, they were originally non-machined. They seemed to brake better than machined rims.

I found a Mavic rim with a pretty similar ERD and double eyelets that I'll probably end up ordering as the replacement.