I ordered my X1 xDrive28i Sport Line during Thanksgiving holidays and just picked it up last Friday. My tires are 225/45R18, Continental ContiProContact SSR Grand Touring All-Season. X1 xDrive28i Sport Line used to have Pirelli Cinturato P7 All Season Run Flat Grand Touring All-Season. Now, it changed to Continental ContiProContact SSR (in Tire Rack, the Original Equipment Tires for X1 xDrive28i Sport Line still point to Pirelli Cinturato P7 All Season).
This is my first BMW and first run flat tires. The driving of Continental ContiProContact SSR tires feels good. I do not feel any bumpy, like other X1 owners observed. I feel even more smooth than non-run flat Goodyear Eagle RSA (on my Inifiniti I30).