Official Tire of IronmanR. Schwalbe has developed a tire specifically for the sport of triathlon. Ambitious triathletes today use special time trial bikes and aerodynamically optimized wheels. The new Schwalbe Ironman is optimized for this set up. In the optional tubeless version, it is particularly fast and puncture resistant. The name Ironman is a trademark of World Triathlon Corporation WTCand is used under license by Schwalbe. In complex wind tunnel tests, Schwalbe determined the tire width that produces the least aerodynamic drag for the entire wheel system. The 22 mm tire width was by far the best. The bulbous aero rims resulted in both the common 23 mm tire width as well as very narrow 20 mm and very wide tires in 25 mm width having a measurable increase in aerodynamic drag.