Basic Concept

• At its most basic level, the swingarm is a spring-loaded metal bar running from the chassis of the bike to the rear wheel and connecting at the rear axle. The idea is to allow the rear wheel to be flexible and move up and down depending on what kind of bump there is on the road. The arm is spring-loaded so it will always return to the same position, in a style similar to the more common fork spring suspension found on cars. Fork suspension, which is fitted to the front wheel of the bike, will not work during cornering, as the motorcycle is leaned over at this point.
  
  

Original Idea

• When suspensions were first fitted to motorbikes, the swingarm was called a swinging fork. This consisted of a pivoting metal piping running from the chassis to the rear axle, with shock absorbers running off to underneath the seat. Although this is still the basic idea of the swingarm, it was only effective at ironing out bumps in a straight line.
  
  

Monoshock

• First introduced in 1977 for racing bikes, the monoshock combined the pivoting arm connected to the rear axle with a suspension spring attached to the chassis itself. As it was no longer attached vertically to the seat, but at an angle to the chassis, the suspension continued to work around corners, ensuring there was always sustained contact between the road and the driving rear wheel. Most modern bikes use an updated monoshock system with a more complex linkage to improve both rider comfort and rear wheel traction.
  
  

Twin-Shock

• As the name suggests, twin-shock swingarms use two springs instead of one. The rear wheel is attached to the chassis using an H-shaped swingarm -- unlike the parallel bars used on the monoshock -- with the two springs running up at an angle to underneath the seat. This is very similar to the swingfork idea, but as the forks were angled, it corrected some of the faults. Swingforks are not used very much anymore on anything apart from large cruising motorbikes such as older Harley Davidsons.