Suspension

How Suspension Works
Imagine a system comprised of a mass (your car), a spring (the torsion bars or coils in strut suspension), and a damper (the shock absorber).

When a mass is connected to a spring and pulled back then released, the mass will bounce back and forward in a bouncy motion that most people will be familiar with. When the spring is in its natural state, neither stretched or compressed, the spring holds no potential energy. Stretching or compressing the spring gives it energy. Essentially the spring acts as a store of energy which it can only get rid of by returning to its natural state. Attaching a mass to one end of the spring, pulling it and releasing it, causes the spring to transfer its potential energy into the kinetic energy of the movement of the mass as the spring stretches or pulls back towards its natural state. As the spring passes this point of its natural state, the mass is travelling at its fastest and has the most kinetic energy and then starts transferring this energy back into the spring, as the spring becomes distorted further away from its natural state.

This bouncy motion would continue forever if it wasn't for friction within the system causing energy to be lost. In the case of a car we don't want the bouncing to continue and want the spring to return to its natural state as soon as possible. This is the purpose of the shock absorber - to absorb the energy of the bounce.

If the shock absorber doesn't absorb enough energy (as would happen if the shock absorber was broken), then the car will bounce too much. If the shock absorber absorbs too much energy then the car will take too long to return to the spring's natural state. If the shock absorbers are working properly then the system will be 'critically damped' and the car will quickly return to its natural position without any bouncing.

Torsion Bar Suspension
Most aircooled Volkswagens use torsion bar suspension both front and rear.

Macpherson Strut Suspension
Super Beetles use Macpherson strut front suspension. This consists of a spring and shock absorber combined into a single unit. This design is the basis of most modern car's suspension. Using this suspension design enabled VW to eliminate the front beam, which contained the torsion bars. The results were more luggage space (with the spare now laying down flat), better handling characteristics, a lower centre of gravity, and lower maintenance.