Four to Five Lug
 

Is the stock s5 suspension and five lug hub assembly interchangeable with a n/a s4 four lug?

It's pretty much a bolt up deal, the only thing is you want the whole rear carrier it keeps you from pressing it apart which is a pain if you don't have the appropriate tools.

I just finished this swap, you will need the entire rear knuckle like SilentNight says. You will need the rotors front and back, front hub assembly with bearings and pads front and back. I upgraded the brake lines to S.S. braided. Other than that, its a pretty easy swap done in a day.

The suspension is the same way?

Im not sure I understand your question, but yes, the shocks and struts are the same.

Another thing, you will need the calipers as well front and back.

i don't think so.....lol