Of springs and dampers
In the last article we stated that spring stiffness choice is based on experience and subjective appreciations, as much as it is on objective science. The determination of the spring stiffness is dependent of the track macro (bumps, kerbs, slope, banking) and micro (asphalt roughness) definitions, the track temperature, the car mass, inertia and aerodynamic properties, the tyre (in itself a dark science) grip, wear and thermal characteristics, the effects that suspension stiffness can have on the car reliability and, finally, driver skill.
Most of these inputs are not easily qualifiable and quantifiable. However, there are two fundamental engineering tools that we can bring into our decision process.
Shapes of things
The first one is the definition of track bumpiness. What are the shapes of the track bumps and how often, and at what speed, do the tyres hit these bumps? This will help in the spring stiffness choice. We will discuss this further in a future article on a quarter car model simulation. That simulation tool allows us to define spring and damper depending what the race engineer and driver are looking for, and the compromise they will accept between tyre grip and wear, ride height consistency and its effect on aerodynamic performance
