Hmmm, that picture was taken after driving it or after it sat for a while? it almost looks like the shape of that rust spot mimics the shape of the caliper.

In any case, brake vibration can also be caused by uneven pad material transfer to the rotor. Maybe you cleaned off a high spot and that was it.

Also, I've had that same jack since 2006 and I recently bought the same one brand new to have as an extra. Stout little thing!

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2006 X5 4.8is