The term softail refers to motorcycles and bicycles that feature a moveable rear suspension system with springs or shock absorbers to absorb bumps.
On motorcycles, the shock absorbers or springs are hidden underneath out of view to give the appearance of a hard-tail or rigid frame.
The word softail is a registered trademark of Harley-Davidson motorcycles coined with the release of the FXST Softail in 1984.
Since then, the word has expanded to include other motorcycles with hidden rear suspensions as well as bicycles incorporating a rear suspension.
In Harley-Davidson motorcycles, the softail frame is designed to look like the hardtail bikes of the past, while still offering the comfort of rear suspension. The shock absorbers are positioned along the axis of the motorcycle, tucked away under the transmission.
There are several Harley-Davidson models with the Softail frame, including the Softail Standard, Custom, Springer Softail, Heritage Softail, Heritage Springer, Night Train, Deluxe, Deuce, Fat Boy, and the Dark Custom Crossbones.
These motorcycles have the same engine, transmission and frame with the exception of the Deuce, which has a 2" backbone stretch, but differ in the choice of fork, wheels and accessories.