A suspension system is made up of many components that work together, to assist in softening the undesirable effects of the surface that a vehicle is travelling on. It works by delicately balancing these effects, whilst still providing the driver with the necessary road response for driving, steering and braking safely.
The two main aspects of a suspension system include the springs and shock absorbers that help control the suspension movement and the network of control rods, linkages and bushes that connect the wheels to the vehicle. This network is intricately designed to be rigid, whilst allowing vertical movement for the wheels.
Suspension gives all the wheels of the vehicle more chance of making contact with the surface especially when driving over bumpy uneven tracks. When you travel at speed, these effects are amplified and driving over smaller track imperfections could now be quite noticeable. A good suspension system will dramatically help suppress these effects.
Springs are an amazing device that can store energy when it’s altered from its original state. The spring can then release this energy when the load is removed and therefore returning it to its original state.
Springs are used in vehicles to help absorb changes in the terrain such as bumps or potholes that would otherwise jolt the vehicle. At the time a wheel enters a pothole for example, the spring releases energy at the time the wheel moves into the hole. The spring would then reabsorb this energy as the wheel exits the hole.
The spring rate is the measurement of a spring’s energy storage and is measured in terms of how much force is required to deflect it by a given amount.
Linear or Fixed-rate BehaviourIs when the spring compresses at a constant rate or measurement to the increase in load placed upon it. For example, if 50kg were placed on a spring and it moved 1cm. The spring’s rate would be 50kgs/cm and an additional 50kg would result in a 2cm compression.
Rising-rate BehaviourThis spring rate is more exponential and is highly suitable for vehicle applications. For example, if 50kg were placed on a spring and it moved 1cm, it may take 150kg for it to move another centimetre. This spring behaviour may allow substantial compressions for medium loads but without fully compressing under heavy loads. The downside to a linear rate spring is that the spring may be rigid enough for heavy loads but too rigid for light loads.
Suspension Arms and LinkagesThe suspension arms and linkages all form the core framework of the suspension system. They all work together to serve a common purpose and that’s to keep everything locked in place, whilst providing the support and leverage where necessary. The design of this framework is very important in ensuring that the suspension system operates as intended and in general, the linkages be sturdy and rigid as possible to eliminate undesired movement.
Shock AbsorbersShock absorbers, also known as dampers or shockies are used to help slow down or dampen the movement of the suspension system. They consist of a piston moving inside an oil or gas filled tube and have various holes and spring loaded valves to control its resistance to movement. Unlike a spring, a shock absorber will keep moving with the force that was applied until the force has stopped or reached its energy limits. When this force is exhausted, the shock absorber will attempt to return to a fully extended position however the weight of the vehicle will limit this travel. In a correctly setup suspension system the shock absorber should be centered to the travel of the device.
Pivot points, which are joints between moving components need to have either restricted movement or be able to rotate freely in the desired way. There are two main types used in suspension systems and they are bushes and bearings.
BushesThese components, also known as bushings are made of rubber, nylon or polyurethane and are generally used between joints where vibration needs to be absorbed. These bushes are used to help absorb road shock, reduce noise vibration and harshness. They are used to prevent steel on steel and minimise movement, which is the main cause of vibration transference, which in turn leads to steel degradation. Many of these bushes are designed to slightly flex to allow for a certain amount of linkage misalignment.
BearingsMetal spherical bearings, also known as rose joints are commonly used to allow free rotation. They are more expensive than bushes; however, they provide a very stiff and solid joint. These components don’t offer the joint the impact absorption of rubber, nylon or polyurethane bushes.