I`m lowered at the rear 40mm and front 50mm with 8j offset 43mm and 235/40/18 tires, front 225, I have a small amount of scrub on the rear with the rear liner screw removed.
Offset is critical to tire choice, if you go 32mm offset you will have stretch a 215 tyre on.
The standard offset on 18" A3 wheels is 54mm, the smaller the offset the further out the wheel sits from the hub.