Point of no suspension (Tech. stuff)


The suspension on a vehicle is a relatively simple mechanical system. Basically, there are two springs on top of each other, which together carry the weight of the vehicle. The upper spring is the main spring of the vehicle, mounted in the suspension, and the lower spring is an air spring, namely, the tire. Usually, when the vehicle encounters a bump on the road, the softest spring (which is the vehicle’s main spring) is compressed and the suspension absorbs the bump, often without the driver being able to feel it inside the vehicle.

Instability

The disadvantage of this simple mechanical system is that it becomes unstable, the weight of the vehicle along with the springs can start to oscillate, and the vehicle is decidedly dangerous to drive because the tires and the entire vehicle become unstable.

Role of the shock absorber

To remove this instability, a shock absorber is used. The shock absorber is located together with the vehicle’s main spring inside the suspension. The shock absorber dampens the oscillation by removing the energy, thus removing the vehicle’s tendency for instability and thus improving the tire’s grip.

Disadvantages of the shock absorber

The use of shock absorbers also has some drawbacks. The disadvantage of normal shock absorbers is that they work best at low speeds. At very high speeds or ultra-high speeds, normal shock absorbers do not work well because they become too stiff and block the movement needed for the suspension to work. The fact that normal shock absorbers become stiffer and stiffer as the speed increases can be seen in their force-velocity plot.

force velocity plot
Force velocity plot for a normal high end shock absorber, where the damping (stiffness) always increases when the velocity increases. This applies regardless of how the shock absorber is adjusted and the trend continues outside the graph given by the manufacturer. This trend is even worse for cheap shock absorbers, which can have severe and uncontrolled increases in damping stiffness. THE REASON that all normal shock absorbers have a force / velocity plot that exhibits an ever-increasing tendency is that normal shock absorbers primarily regulate with valves or shims, both of which are a variation of a hydraulic pressure regulator which always exhibits this increasing tendency. Valves and shims were introduced around the early 1980s and the technique has been intensely refined over the last 20-30 years.

Point of no suspension

As the shock absorber becomes stiffer and stiffer and the trend continues outside the official graph given by the manufacturer, it is not possible to avoid a point (point of no suspension) where the vehicle’s main spring together with the shock absorber becomes significantly stiffer than the air spring (tire).

-According to simple mechanical rules, it is the softest spring that is compressed, and because the main spring + shock absorber becomes stiffer and stiffer, the tire is naturally deformed more and more, when velocity / speed is increased.

-At the “point of no suspension”, the tire is compressed/deformed instead of the suspension absorbing the bumps. Thus, the suspension is technically blocked and no longer works.

How to remove the point of no suspension

The point of no suspension can be postponed or removed completely by effectively limiting the damping at high speeds.

This is why the FAARO principle, which enables the damping to be controlled at high speeds, has been developed. By controlling, limiting or lowering the damping at high speeds, we can postpone or completely remove the point of no suspension.

In other words:

  • It can be ensured that the main spring together with the shock absorber will never be stiffer than the tire;
  • Resulting in a shock absorber that does not block the suspensions natural movements at high speeds;
  • Resulting in a wheel suspension that can absorb high speed bumps, rather than a tire that deforms;
  • Resulting in less tire deformation, better road grip, less tire noise and better comfort