Ok, so it seems that it does not fit.
The 17" BMW Mag has a slight taper on the inside that reduces it from 17"s to just about 15.5"s.
The Front Wheels are actually the problem with the large caliper.
Also the center hub is a bit larger for the 17"mag.

(I suppose in an emergency one could swap front and rear 19's, leaving the 17 at the back.
See pics for clearance difference between 17" and 19" wheels

Attached Images

     

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