I have definitely witnessed the same lip and felt it needed to be removed before even thinking of turning the key.

I have used 4" grinders in the past, but the rotors were always off the car. I am sure there is a spot where you can access both sides of the rotor without hitting the dust shield.

Take a practice run first on the outer lip just to get a good sense of how quickly material will be removed from the rotor. Then start glancing it with simple, well timed strokes... you'll find a speed that suits the proper removal of the lip and you'll become comfortable enough to do the inner lip.

There is no reason to set up some kind of rotating device. Just keep the rotor in place while you are working on a particular section.-----*you can weigh it down with a C-clamp clamped to the rotor surface... the weight will stop the rotor from turning..)

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