Wheel offset determines the wheel's (width remaining the same) location relative to the hub of the car. A higher offset wheel # will bring the wheel in towards suspension components and the inner fender. A lower offset wheel # will bring the wheel away from suspension components and towards the outer fender. The 1 series requires very high offset wheels to fit wide tires for higher grip applications. Our fitments for the 1 series utilize an 18x8.5" ET45 front wheel and 18x9.5" ET58 (EC-7 model) or 18x9.5" ET62 (ARC-8 model) rear wheels. These are spec'd so you have the ability to use a 235/40/18 front tire and a 265/35/18 rear tire without major modifications.
The below graph is a good visual indicator of how the same width wheel with a different offset can have a very different look and fitment.
