I have 18's with a 20mm drop (M Perf Suspension).
I'm at the burgermotorsport page and they recommend:
12mm up front
15mm out rear.
Has anyone tried this, seems pretty aggressive...will be running these with 18" 400's.
2012 335i Mineral Gray
M Performance Whore: PPK|Exhaust|Brakes|Performance Suspension Struts & Springs|Black Kidney Grilles|CF Spoiler and Mirror Caps|Bav Stage 1 upgrade |M Sport 400M|BMWF30.com