The wear sensors are not reusable. I always replace the rotors when I replace the brake pads. I don't consider them reusable regardless what they might measure. They wear just like the pads and go through so many heat cycles over the life of the pads that it is wise to replace them. It is not necessary to replace both the front and rear pads at the same time. If you don't I would use the same brand pads as the other end.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas