In this article we will focus on the leaf springs as they are the most common types of elastic suspension elements. You may say that there are also bellow-type balloons and hydro-pneumatic suspension, but these elements require separate careful studying. Torsion bars will not be considered as they are hardly suitable for technical creative material. Read more technical tips from the best auto parts suppliers.
The stiffness of the elastic element is a force, needed to be applied to a leaf spring in order to stretch it on the unit of length (m, cm, mm). For example, the stiffness of 4kg / mm means that the strength equal to 4kg must be applied to a spring to reduce its length by 1mm. Rigidity is also often measured in kg / cm and gr / m. If you want to conduct the measurements in garage conditions, you can stand on a spring and divide your weight by the number equal to suspension element length reduction.
Driving fluency is and indicator showing the level of car jolting on the road. Natural frequency of the sprung masses of the vehicle on the suspension is the main factor influencing the level of jolting. The frequency itself depends on the ratio of these same masses and vertical stiffness of the suspension. I.e. if the mass is greater than the stiffness may be greater. The problem for the vehicles with lower weight is that right suspension is strongly dependent on the amount of cargo. And the weight of cargo is a variable component of the sprung mass. By the way, the more cargo is placed in a car, the more comfortable (less jolt) the car is until the suspension has completely compressed. The most favorable natural frequency for the human body is such that we experience during a natural for us walking 0.8-1.2 Hz or (roughly) 50-70 oscillations per minute. 2 Hz (or 120 oscillations per minute) are allowed in the automotive industry.
Vehicles, which mass-stiffness balance is shifted towards greater rigidity and higher frequency of oscillations are called rigid and cars with optimum stiffness characteristics for their weight - soft.
Gilbert Nelson provides a case study of leaf springs suppliers and the main elastic elements of the suspension.
Read about the advantages of leaf springs.