Coil spring (progressive)
Without any electric/elctronic regulation at all the the progressive springing offers a high degree of comfort (softer suspension) when the vehicle is not loaded, at the same time, it makes an increased payload possible.
Should the vehicle not be equipped all round with progressive springs, they are, more than likely, to be found on the axle with the more often varying load (mostly the rear).
If you click on the button 'Diagram', you'll see a linear blue line as soft- and a linear green line as hard spring- identification. Both have disadvantages which are compensated by the progressive red line. With
progressive springs, the spring travel increases less than double when the spring load is in fact doubled. The consequence is, with increasing spring travel, the suspension becomes stiffer. There are at least three
possible ways of making a coil spring progressive:- differing wire thickness,
- differing loop diameters,
- irregular spiral-incline.
The above picture shows a space-saving Minibloc-spring. Due to its progressive design, comfortable driving without a load, is combined with the possibility of being able to take on a large payload if necessary.