Challenge makes Handmade Bicycles Tires including Tubulars, Tubeless and Clinchers using Silk, Core Spun Cotton and Polyester ... casings and the highest performance tread rubber in their private Thailand factory. Challenge brand names include the original, iconic Grifo cyclocross tires and Strada, Criterium and Paris-Roubaix road tires. Challenge tests their products by sponsoring world-class Road, Cyclocross, Track, Triathlon and Gravel athletes and teams. Challenge also makes the only seamless latex inner tubes that are used in all of their top level tubulars and are sold separately as an aftermarket product. Challenge also sources industry standard vulcanized tires to supply lower price point product with the same tread patterns for both tubeless and clincher use. read more