had Bridgestone RE050A RFT that had complete flat in the front tire. Even with the heavy engine, side walls of the 245-35-18 tire never full collapsed (meaning the rim never touched the ground). Take a non flat tire, take the air out and let it sit, you will see that the rim is almost to with the ground. Then take a run flat tire and let the air out, you will notice the side wall stays almost the same as when it had full tire pressure. The side wall on the run flat wont flex like a non run flat tire. Drive it at 50-60mph and the car will still handle. Obviously you wouldn't want to drive a run flat with no air for a long lengthy time, but the Bridgestone RE050A RFT did what it was suppose to do... 50-60mph at 50+ miles.