I have the opportunity to get a set of 9 spoke, 8.5J X 18" rims from my friend who has a brand new RS6. These are the stock rims that come with the car, and he upgraded.

My question is, will I run in to issues (turning, rubbing) when I mount these rims on my 2002 A4 1.8T Quattro with Sport package?

Secondarily, would a 235/40/18 best size tire for these rims?

My car currently has the stock 5 spoke 17" rims, with 235/40/17 Dunlops.

Thanks

no 40/18's are too tall

First of all your car's stock tires (2002 A4 1.8t Quattro with Sport package) should be 235/45-17.

To do a plus-one size, your tires should be 235/40-18. So David_K is mistaken - all is OK with that size. Those tires can be mounted on wheels with 8 - 9.5 inch widths, the ideal width is 8.5 inches, so the wheels are OK, too.

How about the 19" 5-spoke wheels from the RS6? Is the bolt pattern 112mm and what size tire would one need for an '05 A4?