[Maximus92]

From what I read square 245/40 or 235/45 is the way to go. I have style 397 8x18 rims.
I'm curious if there could be any problems on fitting 255/40 on 8 width rim? I really like the look of it in the rear, I would assume it won't fit in the front? So i was maybe thinking 255/40 in the back and 245/40 in the front.

Don't track the car, just daily driving it, comfort is priority (widest tire + highest sidewall).

[alohasurftoad]

255/40/18 best fit on 9". min recommended width 8.5". squeeze the beads to fit on 8"? some do, however contact patch and sidewall integrity are optimized if used within the recommended rim width range.

square is obviously better for rotating and getting maximum tread life.

for F3/4 series, widest+tallest on 18x8 ET34 is 245/45/18

https://f30.bimmerpost.com/forums/sh...48&postcount=3

for a 320i 235/45/18 square is what i'd use