I have PSS 275/35/19 on the rear with stock 9.5" wheels and stock ride height, and I rubbed badly with a 15mm spacer. I got away with a 12mm on 265s, but not 15mm on 275s. And I'm running -2.0 camber, too.
2008 M3 Coupe / DCT
// StopTech BBK 380/355 / Pagid RS29 / Motul / Apex Arc-8 / BFG R1S / Ground Control / MS filter / Performance spoiler / BPM tune // Road Atlanta 1:40.77 / VIR Full 2:12.32 / Barber 1:42.20