Hello, we bought an 2010 X5 diesel in January, 31,250 miles and we are still figuring it out. Mostly have wheel questions at this point. The previous owner had 20 inch Sport package wheels installed without run-flats. The rears need replacing and deciding what's the best way to go is perplexing. We bought the car to tour around the country (retired) and desire stability and comfort over high performance. We also have a 1997 Z3, 4cyl and 5 speed, it's in the back of the garage until spring. That's all folks!
Welcome (back) to the club & forums! If your car has no accommodation for a spare, then I'd say you might want to opt for runflats. If your priority is highway cruising & comfort over-the-road, I'd downsize the wheels to the smallest diameter that fits over the front brakes with a width and offset that works both front & rear, and get rft's with as much sidewall height as you can that has a overall dia. as close to stock as possible (to maintain odo accuracy), & if possible, run the same width tires front & rear so you can rotate the tires to even out wear, shooting to fit the same width on the front as the standard oe. width on the rear. A quick look at http://www.tirerack.com/ shows 255/55-18's as an all around fitment - I don't know if 285's would fit on the front - it shows sport package w/ 255/50-19's. I also don't know if sport package has different front brakes that need 19" wheels to clear the brakes; if the sport pkg. is only a wheel upsize, then presumably properly-sized 18's wouldn't present a clearance issue.