Originally Posted by
auchencrow
My theory is that the chain went up and over the large cog, lodged against the spoke protector and caused the wheel to jerk the QR out of position. The chain lurching up like that was too much for the jockey wheel, and it shattered (as they are inclined to do). I think the root cause was improper low gear adjustment.
I'm reading this in a CSI voice over and picturing it happening in a series of slick close up shots zooming along the drive train.