185/50R16 tyre has an outside diameter of 591.4mm
205/55R16 has an outside diameter of 631.9mm
So 205/55R16 has an outside diameter that is 40.5mm bigger than 185/50R16, or a radius that is 20.25mm bigger.
205/40R17 has an outside diameter of 595.8mm and is close to rubbing. So 205/55R16 which is an Audi A3 size tyre will rub very badly. Probably both top and side.
Also, the load index of 205/55R16 tyres is 91 (615kg). This is too high for the lightweight Audi A2. Hence why people who run 185/50R16 tyres which have a much lower load index of 81 (462kg) find the handling so sweet. So ideally you want a load index of about three-quarters the load index of the 205/55R16 tyre, ie. a tyre fit for a lightweight Audi A2 not a heavyweight Audi A3.
People have even had the lower sidewalled 205/50R16 rub on the Audi A2. If you really want 16 inch wheels, perhaps try 195/50R16...but 15" wheels such as 185/60R15 ride so much better.
See this link for standard 15"/16" alloy rims for the Audi A2
Wheels, brakes Aluminium rim hub cap 15
www.oemepc.com
The 5.5Jx15 ET34 rims shown in the above link could be a good option for 185/60R15 tyres. Standard is 175/60R15 on those rims.
Or perhaps 6Jx15 ET29 rims for the 185/60R15 tyre size from the Audi A1 as shown in the below link
Wheels, brakes Steel rim aluminium rim hub cap 15
www.oemepc.com
A third option for 185/60R15 tyres on the Audi A2 could be 6Jx15 ET35 rims from the new Skoda Scala
Check if steel wheels VW W21-19547013091 fit to your vehicle.Tempting prices and free shipping. Buy steel wheels VW W21-19547013091.
www.oponeo.co.uk
5.5J rims would give slightly better comfort than 6J rims when fitted with 185/60R15 tyres as the narrower rim helps the sidewalls to flex more easily, but 6J rims would give the sharpest steering/handling. Car manufacturers in the past, have used both 5.5J and 6J rims with 185/60 tyres.