The 1958 Harley-Davidson FL Duo-Glide motorcycle introduced a genuine rear suspension system, finally giving riders of the big Harleys smoother, modern ride. Prior to the rear suspension system Harley-Davidson relied on a sprung saddle for "rear" suspension, the big Harleys adopted a swingarm with coil-over shocks in 1958. With that, the Hydra-Glide became the "Duo-Glide", upping the ante in the touring market.
Along with the rear suspension the 58' also received other updates including a hydraulic rear brake, a stronger transmission and clutch, better connections for the exhaust headers at the head plus optional white-wall tires. The model characterized “Dressers” and the increasing number of accessories included Royalite saddlebags, a floating Buddy seat with chromed grab rail and dual exhausts.
The Duo-Glide was available as the FL and FLH, (H for Highway).