As of 2015, Bridgestone is developing an air-free concept tire that is similar to Michelin's integrated tire and wheel combination, which is called the "Tweel." Michelin's Tweel features shock-absorbing, load-carrying and handling characteristics that are comparable to modern-day pneumatic tires.
Air-less tires are not supported by air pressure and feature the ability to avoid going flat. Air-less tires have a generally high rolling resistance that cuts down on speed and provides less suspension than regular air-filled tires. Air-less tires are plagued by heat build-up when driven extensively, according to Wikipedia, and they are attractive to cyclists due to the increased risk of normal tires being punctured.