In order to create a new design, it was necessary to have accurate 3D dimensions for all of the components related to suspension and drive-train. After all it would be impossible for a suspension bracket to occupy the same space as the differential.

However, as a benchmark for a custom set−up I used :

  • Modified Sierra uprights.
  • Mushroom top hat adaptors.
  • McSorley 442 chassis with suspension mounts similar to Locost.
  • 195/45/15 − Diameter 556mm.
  • Centre of gravity height = 444.5mm.
  • Chassis to ground clearance = 150mm.
  • Front track 1452mm.

I used a very handy Ms-Excel calculator to ascertain the following factors :

  • Roll Centre vs Bump & Droop
  • Camber vs Bump & Droop

image: MsExcel» Ms-Excel Suspension Calculator

image: MsExcel» Free Ms-Excel File Viewer

Surprisingly, one of the biggest resources for suspension design is the on-line gaming community. Modern computer driving simulation games take ‘modelling’ of cars to incredible extremes. They model everything, not just chassis stiffness, tyres, aerodynamics, gear ratios, suspension geometry etc, but right down to the performance differences between differential oils and how much richer the petrol mixture gets upon gear change! If you don’t believe me surf on ‘Kangaloosh‘ and ‘rFactor‘. Major race teams are now actually using this software to ‘theory test’ their cars on a given virtual race track!

Benchmark :

x axis y axis
Top Pivot Point (from centreline of car) 581mm 386mm
Bottom Pivot Point (from centreline of car) 619mm 186mm
Angle Length
Top control arm angle and length 4.75° 309mm
Bottom control arm angle and length 1.8° 408mm
  • –0.6° Camber
  • 25mm bump / droop gives 2.4° camber change.
  • 2.4° bump / droop gives 47.7mm Roll Centre (Y) change
  • For 5° Roll, roll centre is  147.99(x)mm, 47.5(y)mm

image: Benchmark setup

image: Benchmark Roll

image: Camber vs Bump Droop Travel

image: Roll Centre vs Bump Droop Travel

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