Complex sentence: SunTour was the first component maker to make parts especially for mountain-bikes, the Specialized firm in California fitted these parts to its early mountain-bikes of the 1980s, and together both firms were very successful in the American market-place.
Split into simpler sentences: SunTour was the first component maker to make parts especially for mountain-bikes. The Specialized firm in California fitted these parts to its early mountain-bikes of the 1980s, and together both firms were very successful in the American market-place.