If you study the reviews and keep track of tire development as I have, you'll discover that RFT's, especially Bridgestone, are in their 3rd generation and are mostly as soft as the same type tire that is not run flat. Bridgestone even has an all season that comes with the same tire with or without run flat, the RE960AS, and it tested about the
same.
The
reviews for tires for the 335d sport package are also interesting in that the latest generation of Bridgestone RFT's seem pretty good.
My only complaint so far with my Bridgestone Potenza RE 050AI's has been, compared to past Michelins, is I now have the "usual" loss of air pressure. Michelins seem to be made with materials that minimize air loss compared to other brands in my experience.
The car rides more softly when I inflate the tires a pound or two above the recommended levels too. It wouldn't surprise me that many have problems with their RFT's, including sidewall issues, because they don't properly maintain air pressure, even the small amount before their air pressure monitor systems kick in.
It wasn't until the 2011 models that the latest run flat designs were found, so earlier cars had harsher rides. Reviews from 2009 and 2010 model owners seem to reflect this.
PL