Steve takes a look at the development of car suspension and the most common types found on vehicles.
Also known as cart springs, leaf sprung suspension comprises of a layer of rectangular metal bars, bent and attached at both ends to provide a spring effect as per the diagram above. It is very rudimentary yet durable and most commonly seen on pick up trucks or vans. This is partly due to increase the carrying weight of the vehicle but predominantly to help the vehicle achieve a cheaper tax class in certain counties.
The drawback of this suspension is that it does not offer the same ride comfort of that as springs and damper suspension. Furthermore, the leaf springs can split due to wear and tear caused by age or corrosion.
McPherson front Struts
McPherson Strut suspension Has been the common suspension choice for manufacturers since the late 1960s. Comprising of the spring around a damper and fitted together within a unit which is bolted directly to the car it offers both good ride characteristics as well as reduced repair costs as the unit can be removed from the vehicle very efficiently. When this suspension is used on the front of vehicles the rear often comprises of a spring and damper which are fitted separately to one another band attached to the rear wheels and axel. As the suspension wears out, the springs can crack or snap due to corrosion and the dampers can start to leak hydraulic fluid. You can tell if a spring has snapped as the car will be lower to the ground on the side with the broken spring. Leaking dampers can affect the handling of the vehicle.
Commonly used on commercial vehicles, executive SUVs, modified cars, 4x4 or executive saloon/estate cars air suspension comprises of 4 individual rubber airbags as apposed to springs and dampers. Depending on the vehicle it may be supported by additional dampers, mainly on estate cars or those designed for towing or carrying extra load capacity.
The beauty of air suspension is that the driver can adjust the ride height of the vehicle at a touch of button, either to lower or raise the vehicle height depending on road conditions. The system works by compressed air being pumped into the airbags to improve ride comfort or adjust ride height.
However, air suspension can be very complex and less durable than other types of suspension. Thus meaning, repair bills are often greater and can run over thousands of pounds to repair. You can often tell if there's a problem with your air suspension as the car will sit low to the ground or may not adjust its ride height. If it fails you will normally get a warning message on the dash.
Hydropneumatic /Hydrolastic Suspension
This used to be commonly found on Citroen's, Rolls Royce's and the occasional British Leyland car such as the princess this suspension setup uses a special hydraulic fluid to control the ride comfort and height of the vehicle. The system would often give a very smooth ride, likened to being on a magic carpet but could also be adjusted to give superb cornering abilities as found on the Citroen Xantia Activa family car. It allowed the Xantia to out manoeuvre a Porsche 911 from the same era. The difference between the two is that hydropneumatic spheres use a hydraulic fluid where as hydrolastic suspension uses a gas in the spheres.
Despite it's fantastic qualities of both systems, they are prone to failing by leaks developing in the system or the spheres failing and resulting in large repair bills.