There is a lot of assumptions on here regarding the cause. It’ll be interesting to find out exactly what it was. Most people seem to be pointing towards the calliper coming loose.
I’m not so sure, make me wonder if it was a broken spoke or two.
The rim did collapse, and the calliper has been torn off the mounting, however which came first?
If you look you can see the rear calliper bolt is still there, therefore if the front calliper bolt was missing the rotation of the disc would drag the calliper down agains the disc and not up into the wheel.
I haven’t measured the clearance on mine, but I think the calliper would have to move some distance before contacting the spokes which would need the bolts to be completely unthreaded and I presume this would be noticeable as the travel in the rear brake pedal would change due to the pistons being pushed back.
It’s all speculation until the exact cause is identified.
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