I just experienced my first flat tire experience with the Z4 yesterday. I was cruising and the warning light came out with a not-too-loud "ding" bell. Supposedly the Bridgestone RE090 is good for 90-miles at 50-MPH. I was about 45-MPH from my house when the light came on. So I slowed down to 60-MPH and cruised home at an easy pace. Just for the hell of it, I kind of wiggle the car around to see if I can feel the difference in the handling. Nope. The car felt as though all tires were good. Without that dash warning light, I wouldn't know if the tire were flat. I then had to pass a couple of semi trucks at around 75-MPH. No problem there with the lane change. I contemplated hauling *** home, but I figure Bridgestone may know something about the performance parameters for these tires. So I slowed down to 60-MPH and cruised home (doing 50-MPH on the Kali freeway is a good way of getting ran over or shot). I pulled onto the driveway and whipped out the tire gauge to discover that the driver rear was the one that went flat. You cannot tell by eyeball calibration. The tire itself looks intact as well although I rode it at higher than recommended speed limit. Love it!! ^c The hate part is twicefold: rough ride all the time and REPLACEMENT COST;P You can't fix the tire once it's flat. It's not repairable. I suppose you can try to foam it or plug it, but Bridgestone doesn't recommend repairing run-flats. So the cost for 1-ea Bridgestone Potenza RE050A 255/35-18 including labor from Sears is $371.