uberwgn

Nobody can answer that and I don't know what the roads are like where the car is operated. Personally, I don't think I'd drop below the mfr's Normal load recommendation for the wheel/tire setup fitted to your car. I suspect that Normal load recommendation is the lowest pressure they feel safe about given pot holes, wheel damage, etc.

FWIW, changing wheel diameter and spending a bunch of $$$ may end up in disappointment. I've gone thru this excercise on different cars and ultimately realized the ride quality has much to do with the suspension (springs, shocks) and the wheel diameter possibly not as influential as I had hoped for

Just as a data point, my A4 is fitted with the sport suspension option which includes 18" wheels and a very cushy Pirelli 40-series tire. This configuration yields a smoother, more comfortable ride than the 17" Michlein 50-series snow tire pkg I run during winter months. (I live/drive in suburban Boston MA and the roads are frightful.) So, bottom line is that tire selection can have quite a significant impact on how a car feels over poor roads. Some tires are just a lot better. You could end up switching to a smaller diameter wheel and different tires and gain no improvement in ride quality. Spend adequate time doing your research (Tire Rack reviews, Gary, etc.) so you end up with a tangible benefit.

feirstein

Audi's move away from 16" tires has resulted in a significantly harsher ride with little if any gain in performance. It is all about style and ego, in my opinion.

wieRS5

Try Vredestein Ultrac Vorti, huge improvement in comfort over the Dunlop or Conti's on the S5!