[Artmasterx]

I believe you are starting to push the envelope with an 8.5" up front, and you would certainly have to take care and make sure that the offset was appropriate (so that is didn't rub the strut or the wheel well). I know with an 8" width and a 40mm offset you will be ok (probably anything 35-45mm would be ok). Gill@Tirerack can certainly help you understand what wheel/tire combinations are doable.

Actually, the only reason to run 8.5" width would be if you wanted to run something like a 255 width tire, which you certainly can't run up front with stock setup. Honestly, if you run 225's all around, stick with a 7.5" (et40-50) or 8" (et 35-45) width.

Is you compare the stock 128i sport setup, you have 7" et47 in front and 7.5" et47 in rear. This puts the external face of the wheel 41.9mm (front) or 48.25mm (rear) from the hub face. To match this with a 7.5" or 8" wheel so that it looks like stock, you would need the following offsets:

7.5" --- 53.3mm (front) --- 47.0mm (rear)
8.0" --- 59.7mm (front) --- 54.6mm (rear)

In reality these 50+ offsets will not be available (and may rub the strut), so you end up with a slightly more aggressive looking wheel face that is a little bit farther to the outside of the car.

So if you went with a 17x8 et40 (a very common combination), then your wheels would "stick out" about 3/4" (front) and 3/4" (rear without sport package) than your stock non-sport package wheel setup.

You may be able to find something with a 47mm offset that would reduce this to about 1/2", but it can be difficult, especially in 17". Though I know that some of the OEM BMW wheels, on the Z4 for example, had offsets of close to 50mm.