Wheel Size on Speed3

So i have been looking at wheels for an 08 Speed3, Crystal White. I am looking at the Konig Illusions Blues. But i keep seeing different offest numbers. I am new to these sort of things and i am used to buying rims that say 235/18/70. Is the offset the profile of the tire? This is really driving me nuts and pissing me off. lol
 
Correct me if I'm wrong, but 18 is the size of the rim/tire. 70 is the profile(which seems really tall...SUV-like). Stock ms3 wheels are 215/45/18.
 
70 is truck profile.... 235 width tires will more than likely rub without a fender roll
 
Back