Suspension springs are the link between wheels and car body. Their primary task is to compensate uneven road surfaces and thus provide an assurance of high levels of ride comfort. Secondly, they must ensure...
Suspension springs are the link between wheels and car body. Their primary task is to compensate uneven road surfaces and thus provide an assurance of high levels of ride comfort. Secondly, they must ensure that the wheels always have safe contact with the road regardless of its condition. Reliable transmission of drive, braking and transverse forces relies on these requirements being met. As such, suspension springs are one of the most safety-critical components of modern vehicles. They affect handling, roadholding and braking performance.
From the point of view of design, there are suspension springs with linear and progressive spring rate. With linear springs, the spring force increases in proportion with the extent to which they are squeezed together. Progressive springs start with a soft characteristic curve and become harder the further they travel.
The following types of spring are primarily used in today's cars:
Depending on the vehicle manufacturer's specification, suspension springs are manufactured from constant wire (same wire diameter across entire spring length) or inconstant wire (varying wire diameter across spring length). Where inconstant wire springs are concerned, it is said that there are two springs in one: one soft and the other strong. Progressive mini-block springs, for example, offer high levels of ride comfort at low vehicle load and low compression at full load. The spring is therefore "soft" at low vehicle load and "strong" at full load.
Quality suspension springs make a significant contribution to increased safety, in particular if vehicle loads are high, road surface quality is poor and weather conditions are bad. Where inconstant wire springs are concerned, a higher load (whether due to vehicle occupancy or poor road surface quality) activates the stronger part of the spring. As a result, the spring generally becomes stiffer. This progressive rise in spring rate gives the vehicle stable roadholding characteristics. There are also two more positive side-effects:
Suspension springs from well-known suppliers are delivered with optimum protection against corrosion and damage ex-works. For example, plastic hoses at the ends of suspension springs prevent irreparable surface damage (preventing rust from taking hold) and safeguard quiet and smooth operation. Furthermore, today's design stops contact between the windings, thereby protecting the springs. Under normal operating conditions, suspension springs will last the lifetime of a car and do not require any particular care. However, they should undergo visual inspection when wheels are changed and during service work. In the event of visible damage to a spring (a tear or a fracture, for example), a replacement must be fitted by a garage.