Dampers control the rate of body movement by generating a resistive force – converting kinetic energy to heat energy within the damper fluid.
An overdamped response in the low-speed range leaves the body sluggish to settle in response to input. The settling period of an underdamped response is also sub-optimal as the body oscillates around its equilibrium position.
Either extreme results in an increase in the time required to assume the desired yaw rate. From a purely analytical point of view, something close to a critically damped response gives a decent baseline performance in this respect and is the aim of damper tuning.
In a similar way to roll stiffness, dampers influence the LLTD in transient phases of cornering by affecting wheel loads. The axle with highest compression damping will receive a greater proportion of wheel load during corner entry phases.
In corner exit, this relationship reverses and the axle with a larger proportion of rebound damping sees reduced wheel load. It’s another tool that can be used alongside the spring to fine tune the dynamic balance of the chassis.
Dampers also have to manage the effects of high frequency road inputs on the unsprung mass (> 0.15m/s). Perturbations in the track surface influence contact patch pressure variation so keeping this as low as possible allows the grip generated in lateral and longitudinal manoeuvres to be optimal.
With high frequency inputs, the kinetic energy given to the unsprung mass can be considerable. If the damping coefficient is too low, control over the wheel is lost as this energy is not sufficiently absorbed.
As the wheel travels over a bump, low damping can lead to the tyre completely leaving the track surface. Finding the sweet spot can require some work!