What Is Swingarm Suspension & How Does It Work?
The motorcycle rear suspension mainly consists of a telescopic shock-absorber on each side and swingarms. In some countries, manufacturers call a swingarm a "swinging arm". However, its original name was swing fork or pivoted fork. However, it is the main part of the rear suspension setup of most modern motorcycles and ATVs. It holds the rear axle firmly while pivoting vertically. Hence, the name. It allows the suspension to absorb the road shocks.
Initially, motorcycles did not have a dedicated rear suspension set up. This is mainly because their frames were little more than stronger versions of a bicycle’s typical diamond frame. The manufacturers tried many types of suspension, including the leaf-spring, suspended swingarm, and cantilevered coiled-spring type. The plunger suspension, in which the axle moved up and down the two vertical posts, became popular right away after World War II. In the latter, the movement in each direction was against coiled springs.
Some manufacturers use swingarm designs for the front forks which are more robust than telescopic forks. Particularly, sidecar motocross outfits frequently use swing arm front forks. Some manufacturers used swingarm for the front suspension of scooters. In this case, it helps in simplifying the scooter’s maintenance. In motorcycles with shaft drive, the shaft housing formed the left side swingarm.
Types of swingarm:
- Swinging fork
- Parallelogram suspension
Swinging fork – This design consists of a pair of parallel pipes holding the rear axle at one end while pivoting at the other. Manufacturers mounted a pair of shock absorbers just before the rear axle and attached to the frame, below the seat rail.
Cantilever – This is an extension of the swinging fork where a triangular frame transfers the movement to compress shock absorber/s generally mounted in front of the swingarm. The Matchless, HRD-Vincent Motorcycle and Yamaha used this type of swingarm. However, on the Harley-Davidson Softail, it works in reverse order with the shock absorbers get extended rather than being compressed.
Watch swingarm in action here:
Parallelogram Suspension was first launched commercially in 1985 on the Magni "Le Mans". Magni called this system Parallelogrammo. However, other manufacturers developed various parallelogram systems.