Single-speed bicycle on the situation, a messenger may prefer a mountain bike based single-speed, which can roll over many obstacles, or a fast and light road bike-based single-speed. In the United States market, bicycle companies such as Bianchi, Cannondale, Fuji Bike, KHS, Kona, Raleigh, Giant, Specialized, Swobo, Felt, Trek and Niner all have produced and marketed single speed bicycles. Because most full suspension frame designs either have a single pivot that is not concentric with the bottom bracket, or a linkage with a variable center of rotation, the distance between the bottom bracket and rear axle varies throughout the suspension's travel. This
Trek Bicycle Corporation a few years Trek had outgrown its original "red barn" manufacturing facility—a former carpet warehouse. Recognizing the need for expansion, in 1980 Trek broke ground on a new corporate headquarters on the outskirts of Waterloo. Company co-founder Dick Burke would later recall that "it wasn’t until we built the new factory that we became a business." With more factory space available, Trek expanded its manufacturing to include complete bikes. In 1981 Trek entered the steel road racing bike market, introducing the "Pro" line, including the 750 and 950 models, and in 1983 Trek built its first mountain bike, the 850.