RFTs or run-flat-tires have one of the two supporting systems. One is the self-supporting system in which a reinforced sidewall construction is featured to continue to support the vehicle if the tire loses air pressure. The second one is the ring supportive system in which a ring of hard rubber or some other structure supports the vehicle when the tire loses air.
The best run-flat-tires are capable of running when the tires are flat or without air pressure. They allow your vehicle to travel smoothly to somewhere safe and out of harms way to get a replacement. These run-flat-tires work best with the vehicles equipped with a Tire Pressure Monitoring System (TPMS).