Thanks for the tips, appreciate it. At least the rotor is very worn, so there definitely is a significant lip. Replacing them is in my to-do-list for the summer. Anyway, I will try to find time to check the rotor and surroundings this weekend, at the latest next week. I'll report back what I found.

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09/2003 X5 3.0i
02/2003 X5 4.6is (non-runner)