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Suspension Geometry: Theory vs. K&C Measurement
Technical Paper
2008-01-2948
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
Automotive suspension geometry describes the kinematic movement of a car's suspension based on a theoretical analysis of measured or designed points. This geometric analysis can be done with pencil and paper on a drawing board or with simple physical models, but is more commonly analyzed by the means of specialized software. By contrast, Kinematics and Compliance (K&C) machines measure suspension parameters as loads are applied to an existing chassis and vehicle suspension.
This paper will compare the two approaches as applied to a stock car racing chassis. Significant agreement between the theory and measurement will be demonstrated. Significant differences such as tire deflection will be explained. Additional differences due to compliance of “solid” parts will be described.
The paper will also describe suspension parameters which can be measured directly, such as camber and toe, and those which must be calculated, such as caster, kingpin and, instant centers. It will also compare kinematic analysis with force-based analysis and show how K&C force measurements relate to both.
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Citation
Mitchell, W., Simons, R., Sutherland, T., and Keena-Levin, M., "Suspension Geometry: Theory vs. K&C Measurement," SAE Technical Paper 2008-01-2948, 2008, https://doi.org/10.4271/2008-01-2948.Also In
References
- Best Tony et al. “Design and Operation of a New Vehicle Suspension Kinematics and Compliance Facility” SAE Paper 970096
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- Coovert, D.A. et al “Design and Operation of a New Type Suspension Parameter Measurement Device” SAE Paper 920048
- SPMM Calculations Reference Manual Anthony Best Dynamics, LTD Bradford on Avon, England September 2006
- Vehicle Dynamics Terminology SAE J670e SAE 1952 1976
- Racing by the Numbers WinGeo3 suspension geometry computer program Wm. C. Mitchell Software Mooresville, NC 28115, USA
- Racing by the Numbers BumpSteer computer program Wm. C. Mitchell Software Mooresville, NC 28115 USA
- Milliken, W.F. Milliken, D.L. “Chassis Design - Principles and Analysis” Society of Automotive Engineers 2002