Swingarm

Immediately before and after World War II, the plunger suspension, in which the axle moved up and down two vertical posts, became commonplace.

Swinging fork - the original version consisting of a pair of parallel pipes holding the rear axle at one end and pivoting at the other.

A pair of shock absorbers are mounted just before the rear axle and attached to the frame, below the seat rail.

The HRD-Vincent Motorcycle is a famous early form of this type of swingarm, though Matchless used it earlier, and Yamaha subsequently.

The Harley-Davidson Softail is another form of this swingarm, though working in reverse, with the shock absorbers being extended rather than compressed.

[clarification needed] Extended swingarms - are often used by drag racing motorcycles (called dragbikes) to keep their center of gravity as forward as possible, which reduces the tendency to wheelie at the start.

[4] "Squat" occurs because the top of the final drive chain run pulls the swingarm upwards; "shaft-jacking" occurs because the shaft drive bevel gear tries to "climb up" the large bevel gear in the wheel hub, thereby pushing the swingarm downwards and away from the frame.

A practical way to minimise squat on a chain-drive bike is to locate the final drive sprocket as close as possible to the axis of the swingarm pivot; the ideal solution is to make the final drive sprocket and the swingarm pivot concentric, as was done on the Hesketh V1000.