Race Engineering: Racing car damper ratios

Typical racing car damper ratios are 0.65-0.7 in ride where 1 is 100% critical damping.

This compares to 0.2-0.3 in a passenger car.

There is a lot more to damping that damping ratios.

  • Tyres don’t like surprises
  • For maximum grip the aim is to minimise contact patch load variation
  • The challenge is to optimise for heave, pitch, roll and skew with only 4 dampers – one on each corner.
  • You will target different rates depending on whether you’re targeting ride (body control), grip (contact patch), aero (minimise pitch and max body control)
  • 1/4 car models are helpful but the front is connected to the back so half car is the minimum
  • Tune for linear rates then add “nose” at lower speeds
  • Driver feels lower speed adjustment (up to about 50-75 mm/s)
  • Grip is influenced greatly by higher speed damping driver can’t feel – especially around wheel hop frequency (circa 10-15 Hz typically)
  • The vertical tyre stiffness can change with frequency of road inputs – there are papers on this.
  • Road roughness will have an impact on grip so it is important to know what surface you are on – these have been profiles with PSD’s in military use.
  • How freely an individual damper transitions from bump to rebound can have a big effect – there is more than just the force velocity curve to consider with dampers.

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