https://f30.bimmerpost.com/forums/sh....php?t=2094283
in the thread above, kif30ki has 265/40/18 @ ET40 at the rear. your setup will poke 5mm more...
235/40/18(25.4")+265/35/18(25.3") since the diameters are smaller than OEM, speedo will read higher and odometer will accrue higher, than actual.
imo, the rear offset needs to be at least ET40 but ET42-45 would be better
are those the only sizes for the rims you're thinking about?