Winter Wheel Fitment Help

[JonBoyS4]

Another fitment question here, still trying to understand how to figure this out. I have a b6 s4 with aftermarket wheels on which I bought with the car which are 18x8 et35.

I'm trying to figure out if I can fit an A5 OEM wheel with 18x8.5 et29. I'm considering buying a set of these for the winter.

Would my 235/40R18 tires fit these wheels?

What would the proper size snow tire be?

I am also on H&R lowering springs, so a bit lower than stock ride height.

Thanks for helping out a noob.

[JonBoyS4]

So after some more searching I've found that I will likely need hub-centric rings to make these wheels work.
B8 A5 wheel center bore = 66.6 ; B6 S4 wheel center bore = 57.1
Should be able to find those pretty reasonably I believe.

These are the style wheels I'm looking at, I believe from a 2010 a5 premium plus. The dimensions are 18x8.5 et29.

http://www.finishlinewheels.com/prodimg/ALY58825U.jpg

Still not 100% sure on fitment though.
If I understand things right, moving from my current 18x8 et35 to a 18x8.5 et29 adds .5" to the wheel width and 6mm to the offset? So these wheels would likely poke out about 12-13mm further than my current wheels...about .5"? Can anyone confrim this?

So now I just need to figure out if the wheels poke .5" more, will they rub, right? I believe the inside fitment stays the same here, but the outside I need to make sure won't rub the fender.

Sorry for the basic questions, I'm learning on the fly here and trying to do it without physically bolting them up to see.
Any additional insight is appreciated.

[VMRWheels]

18x8.5 ET29 will be a bit of an aggressive fit and unless you have rolled fenders, it will most likely rub. If you plan on going with an 8.5" width, I'd stay clear of anything more aggressive than ET35.