What Makes Up A Cars Suspension System?
A cars suspension system consists of tyres, springs, shock absorbers and linkages that connect the car body to the axles/wheels. These components make up the core of a suspension system, however, depending on the suspension design in certain vehicles, additional parts may be present.
What Is A Car Suspension Systems Role?
The suspension system allows relative motion between the wheels and the car body. The relative motion is essential for maintaining a good ride quality whilst driving.
When a car travels over a bump/pothole, the suspension system negates the large forces acting on the wheels travelling through to the car body.
In addition, to ride quality, the suspension system must provide suitable handling capabilities to allow the driver to maintain control. Constant contact between the wheels and the road at all times results in good handling.
How Does The Suspension Work?
Suspension systems work by dissipating energy received by irregularities in the road, therefore, removing impact forces. The primary mechanism used for achieving this is by converting the force/kinetic energy into heat. The core components of the system for achieving this are springs, dampers and struts.
Car Suspension Parts
Springs
The job of springs within the car suspension system is to absorb and store the energy when travelling over bumps. The energy is absorbed and stored in a spring when compressed.
How much energy a spring can absorb is dependent on its spring rate. A spring rate is defined: the force required to compress the spring by a set distance. The length of the springs and their material are contributing factors for a spring rate.
Different types of vehicles require alternative springs rates depending on their load. For example, a heavy-duty truck and car will need springs with contrasting spring rates.
Having spring with the correct spring rate is essential for isolating the vehicle from the road. A spring rate that is too high leads to an uncomfortable ride for its passengers.
However, when driving a loaded heavy-duty truck, a high spring rate is required due to the load. When unloaded, the spring rate will be higher relative to the vehicle’s weight, leading to an uncomfortable ride.
Springs within suspension systems on vehicles take a range of shapes, with the two commonly used being coil springs and leaf springs.
Coil springs are helical springs that are in a variety of systems and one most people have seen. Leaf springs are used on solid axles, which means they are suitable for trucks and trains. Leaf springs are one of the oldest forms of springing and have a higher energy storage capacity compared to coil springs.
However, if only springs were present in the suspension system the car would continuously bounce when travelling over bumps and turning. This is where dampers come in.
Dampers
Shock absorbers are a type of damper, and their function is converting kinetic energy into heat. The shock absorber contains a piston with holes in it, which travels linearly up and down and pressurised oil. As a damper compresses, the piston travels upwards, compressing the oil.
The oil is forced through the small orifices on the piston under compression. As the orifices only allow a small volume of fluid through it, it slows down the motion in the shock absorber, slowing down suspension movement.
Whilst compressed and passing through the orifices, the oil is heated, which converts a portion of the kinetic energy to heat, removing any energy left from travelling over a bump.
Velocity-sensitive dampers are frequently used on modern-day vehicles. These types of dampers provide more resistance as the speed of the suspension movement increases.
Struts
The combination of coil springs and a shock absorber in one device is referred to as a strut.
You will read that it is also sometimes referred to as a coilover. The term is a shortened version of “coil spring over shock absorber”. In this configuration, the coil spring and shock absorber are considered separate components.
However, sometimes coilovers are struts, but not all the time. The main difference between a coilover and strut is their adjustability and customization.
How Do The Components Work Together In The Suspension System?
A car consists of sprung and unsprung mass. Sprung mass is a mass supported by suspension e.g. car body, and unsprung mass not supported by suspension e.g. axle.
When a wheel of a car travels over a hole in the road (which is common in the UK because of potholes being everywhere), the spring will store the energy which would have caused the car to bounce. The stored energy in the spring is transferred to the damper and converted into heat.
Without the presence of the damper, the car will bounce on on-side causing a reaction on the other. The result will be a large oscillation between each side of the vehicle bouncing until the force eventually drawn out.