Put the car up on the jack stands and lock steering wheel so nothing moves. Now get one of those laser levels and clamp it to the brake rotor flat surface. Turn laser pointer on and mark it's position on the garage wall. Do your replacement, and then adjust it to the same marked position. Car needs to be stable and installation of the laser level should be repeatable. Worked for me very good on ML430. And you have nothing to lose to try this method.
Mike