Trek being what they were, models evolved as the years went on. The x20 complete bicycles were usually touring bikes: 520, 620, 720. In different years they shared frames with other 5xx, 6xx, or 7xx bikes. A 500 would usually be a sport bike or sport-tour bike, where the 520 is set up as a touring bike.

Early on Trek had two frame geometries, three materials, and dozens of build kits. As they went on the frames became more specialized.

Models changed a lot from year ot year, even in frame details like rake. Not all 500s would ride like all other 500s, over the years.

Road Fan