I just recently experienced similar on my 190 on a rear. Was my first time into MB brakes. Thought it was really strange that only the outside pad was worn until I removed the caliper and realized there was a piston on both sides unlike the typical car with a single piston. Was definatley over-engineering as the pads themselves were tiny.

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You can't always get what you want, but if you try sometime you just might find you get what you need.