definitive tire, wheel, and offset thread

[bmwade]

Resurrecting a pretty old thread here... before I go and buy my brother's stock wheels from him, what will I need to make them fit?
Me: 2003 RS6 (see sig)
Him: 2012 S5 Coupe Prestige - 255/35R19

I know I need to adapt the hub from 57.1mm to 66.6mm, but any guesses on the thickness of the spacer?

Thanks
Other_Erik

I think that's what my wheels were off of. I used 15mm hub-centric spacers and rolled my fenders to stop the rubbing.