[s-cars] Wheel offset question

[Ivan Demkovitch]

List,

I have 15" wheels on my car and trying to get ready for BB conversion. Found 
17" RS4 OEM wheels for sale. As I understand they are 43mm offset and I need 
35mm

What is this 8mm? Wheels will sit deeper and I need spacers or they will be 
more "out" ?

How critical is that for handling? I have Bilstein Sport & H&R suspension.
Planning on running 225/45/17 or 234/45/17 tires.

Thanks!
Ivan
93' S4