Are the SD systems different from the 300D W123's? Just wondering, as the right rotor on my '83 just almost fell off after the caliper was removed in preparation for changing out the CV shaft. Its possible that the e-brake shoes are adjusted out quite a bit, and that there is a lip on the drum somewhat like outside the main pads after some wear has occurred. Also the hex bolt in the center of the hub holds the CV shaft in place, don't remove that one!

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150