I have owned a couple of Audis, and I used to sell them. Audi (and VW) do not deserve the reputation that they have. I have my own reasons for this opinion which I am not going to air.
In my experience of BMWs with Self-Supporting tyres, or so-called 'run-flats', ( 4 to date owned, more driven), the combination of 18" wheels with M Sport suspension is a big no-no if any sort of ride comfort is required. That is why we stuck with 17" on our 335d SE, as well as now the tyre pressures have been raised to 2.5 bar front and 3.0 bar rear with just two people on board.
best wishes
David
p.s. The motoring press are sheep, do not base your decisions on their verdicts. Try for yourself. HTH.
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