Here's more Evidence about the Nature of GRIP and a bit more "technical stuff" that might interest you....
In the video below, you can see shaker rig (or 7 post rig) tests for road cars compared to race cars.
The road cars have the wheels oscillating and the body of the vehicle stable. The aim is to isolate the driver from the external disturbances created by the vehicle driving along the road. To achieve this we need soft springs.
The race cars are much more stiffly sprung. You can see a lot of the external disturbance being dissipated in the chassis of the car. This is the opposite of the road car scenario. See the movement of the chassis in the Red Bull shaker rig video. The big movements could be major disturbances, kerbs etc where obviously softer springs would help. But at other times, you can see the stability of the contact patch versus the chassis of the car movement.
Stiff springs minimise Contact Patch Load (CPL) variation. This helps to keep the rubber keyed into the road surface during cornering. Too much spring stiffness, however, will degrade braking and acceleration.
How Do We Make Grip at the Tyres?
Check Out the Difference.... Road Cars: We minimise disturbance for the driver..... Racing Cars: We minimise disturbance at the tyre contact patch.
Check out this shock position data...
As well as the larger movements of the shocks that result from weight transfer (pitch and roll), you can see very fast up and down movements of the shock (high frequency “vibration”). If we can reduce these oscillations, then tyre grip improves. Part of the reduction in high frequency oscillations comes from adjustments to the shocks . It is the so called “high speed adjuster” that controls the high speed movements of the shock shaft.
Note on Shock Absorbers
You have to choose the springs first, then shock settings. The 7 post rig tests show that you need the high speed area of your shock to be quite soft - probably a damping co-efficient around .5 or less. So for grip, we need stiff springs and soft shocks, at least in the high speed area of the shock valving. Contrast this with the need to provide stability by controlling the body movements associated with weight transfer in racing – the slow shaft speed area of the shock. Here we might expect a damping co-efficient of around 2.0.
The Effect of Stiction, Binding, Looseness, and Poor Lateral Stiffness...
All of these factors hurt grip. To the extent that you have these present, you have to run softer springs. For instance, historic race cars run significantly less spring than modern production based race cars. A specially prepared production car with very stiff roll cage and bushes replaced with spherical bearings can run stiffer than our recommendation.
