The E92 GTS ran a 255/35/19 and 285/30/19 on the ZCP wheel equivalent. The issue is the Mich P4S doesn't come in a 285/30/19. The older PSS now does come in a 285/30/19. I ran this setup on my 2011 and 2013 E92 M3 before I moved on to VMR V810 flowformed wheels in 19X10 and 19X11 now with 275/30/19 and 295/30/19.
That all being said the 255/285 setup is a perfect fit IMHO. Here is a pic of my 2011 with the 285s out back.
