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Roll Centre Height

Roll centre height is measured in RACE software using a force based test.  The basis for this test is shown in the diagram below.  A lateral cornering force is applied at the tyre contact patch and the resulting lateral and vertical forces generated by the suspension are measured.  The roll centre is the height of the intersection of the hypotenuse of Fy and Fz and the vehicle centre line.  The roll centre in RACE reports is presented as both the force gradient Fz/Fy and the calculated roll centre height in millmetres using this force gradient and the suspension track width.

On production vehicles roll centre heights can vary considerably between different manufactures and vehicle types.  On front axles they typically range between 0-100mm and on rear axles typically between 50-150mm.  In general, sports cars are towards the lower end of both ranges, with saloon cars somewhere in the middle and SUV’s towards the upper end.  These numbers are just generalisations across a wide range of production cars, there are always exceptions and outliers when it comes to roll centre heights.