Some drag is normal with disc brakes. If you were getting enough friction to be noticeable when driving the brakes would be getting hot. It is likely there is no problem at all.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine