Lesson learned: since the Brake Caliper Piston is on the inside, there is more wear on the inner pad vs outer pad. So once the OUTER pad is 6 mm, the INNER pad is about 3 mm.

In theory (if you are short of budget), you can unplug the sensor (or short both wires to turn the dash light off) and keep driving until the OUTER pad is ~ 4 mm and the INNER pad is 1-2 mm, Then replace it then.

Throwing away brake pads with 6 mm is a waste of natural resources imo...
With 6mm, you can get another 20K-30K miles. The INNER pad is the problem bc it wears more than OUTER pad...

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT