Your 2 Series has a range of widths and offsets that it can accommodate. Putting an 8.5 ET35 in the front will limit you to a 225/40/18 tire unless you're willing to modify your fenders or have the ability to add negative camber.
For those who want to run a wider tire on the 8.5" wheel, we generally spec out an 8.5 ET42 (ET45 + 3mm spacer) which allows for a 235/40/18 tire. You also have the option to run a 9.5" rear wheel with a 255/35/18 tire.
Here are a couple of pictures showing what each would look like.
Staggered
Square
