Spring Stiffness

The common idea of spring tuning in simulations is to soften the front springs to reduce understeer. And although that’s true, it’s not always easy to remember why.

In this example, we have a car with a stiff rear spring and a soft rear spring to compare.

The spring stiffness affects your car balance in two ways.

First, the aerodynamic effect.

A stiffer rear spring keeps the rear of the car higher, thereby increasing the baseline rake. This pushes the aero balance forward, especially in the mid-speed range (around 120–180 km/h). From an aerodynamic standpoint, that creates oversteer — or simply put, a more dominant and responsive front end.

Second, the mechanical effect.

When the car corners, the rear tires must absorb a greater portion of the load transfer. The stiffer the rear spring, the more pressure is put onto those tires. When a tire is pressed too hard onto the tarmac, its coefficient of friction drops slightly. The tire deforms, overloads, and loses a bit of grip compared to the front.

So not only do we shift the aerodynamic balance forward, but we also rob a bit of mechanical grip from the rear tires, making the front tires more effective.

The same logic applies to the front springs.

Stiffening the fronts reduces dive under braking and moves the aero balance rearward. Mechanically, it also makes the front tires less effective, creating a natural balance of understeer under braking.

This is why one click of spring's stiffness can have such a dramatic effect on the car's balance