Why did airless tires fail?

Airless tires have not exactly failed but have struggled to achieve widespread adoption for passenger cars on highways due to several technical, economic, and regulatory challenges that have slowed commercialization. Early concepts like Michelin Tweel introduced in 2005 for skid steers and mowers worked well off-road but faced downsides for cars including harsher ride and more vibration because they lack air cushioning, higher road noise, increased heat buildup at high speeds due to flexing spokes causing material degradation, heavier weight affecting fuel economy and handling, and higher manufacturing cost than traditional pneumatic tires. Performance issues like debris clogging in open spoke design and less uniform contact patch affecting handling also contributed. Regulatory hurdles, as airless tires must pass DOT and NHTSA Federal Motor Vehicle Safety Standards for high-speed endurance, strength, and performance, and so far no airless tire has received full approval for regular passenger cars on public highways, limiting market. Consumer acceptance due to unusual look and uncertainty about repairability also slowed adoption. So airless tires did not fail in concept, they succeeded in low-speed off-road applications like military, construction, lawn mowers, and are still in development for cars, with Michelin Uptis aiming for approval, but they have not yet overcome comfort, cost, and high-speed durability challenges for highway cars.