I don't need to take the bolt off to remove the rotor (as noted above) I just need more effort on the hammer.

Good idea about the lug nut - I'll try that when I take it off tonight.

FWIW - I am investigating a grinding/scraping noise from the rear and I wanted to know the size in the event that I needed to get the rear wheel bearings out. However - this also means that I'd like to not have to replace my rear rotors and am being cautious with the amount of force that I'm applying.

My guess is that its related to the parking brake mechanism - I can spin the rotor and feel/hear the noise in one particular part of the rotation.

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE