ABSTRACT The paper presents a method for the indoor testing of road vehicle suspension systems. A suspension is positioned on a rotating drum which is located in the Laboratory for the Safety of Transport at Politecnico di Milano. Special six-axis load cells have been designed and used for measuring the forces/moments acting at each suspension-chassis joints. The forces/moments, wheel accelerations, displacements are measured up to 100 Hz. Two different types of test can be performed. The tire/wheel unbalance effect on the suspension system behavior (Vibration and Harshness, VH) has been analyzed by testing the suspension system from zero to the vehicle maximum speed on a flat surface and by monitoring the forces transmitted to the chassis. In the second kind of test, the suspension system has been excited as the wheel passes over different cleats fixed on the drum. By analyzing the forces and the acceleration measured on the suspension system, a set of performance indexes has been derived from the analysis of the data both in time and frequency domain. A simple mathematical model of the tire/suspension system has been derived and validated to analyze the relative effect of the road irregularity and of the tire/wheel unbalance on an actual suspension dynamic behavior. It has been shown, that the direct measurement of the forces and moments at the suspension-chassis joints is an effective way for understanding the vibration and harshness suspension performances. INTRODUCTION The vibration of the vehicle chassis depends on the tire, on the suspension geometry, on the stiffness of the springs, on the damper setting, on the suspension structural features and on the geometric tolerances of the suspension components. Due to these many factors influencing the chassis vibrations and harshness (VH), it is rather difficult to model the suspension vibrational behavior [ 17]. Experimental measurements are necessary to obtain a reliable estimation of the loads acting at suspension/chassis joining points for comfort and durability purposes. The main research activity described in the paper is related to the measurement of VH performances up to 100 Hz in order to include the tire dynamics and the effect of the tire/wheel unbalance. A car suspension is positioned on a rotating drum which is located in the Laboratory for the Safety of Transport at Politecnico di Milano. Special six-axis load cells have been designed and used for measuring the forces/moments acting at each suspension-chassis joints. The load sensors are positioned between the bushings and the fixed structure (which represents the car chassis). In order to reach the adequate compliance level a new 6-axis (force and moments) sensor has been designed because no commercially available sensors could be used [ 4]. The analysis in the time and frequency domains of the measured forces transmitted to the car chassis can be performed by the RuotaVia test rig in order to characterize the dynamics of the tire/ suspension system. Two different types of test have been performed. The tire/ wheel unbalance effect on the suspension system behavior has been analyzed by testing the suspension system from zero to the vehicle maximum speed on a flat surface and by monitoring the forces transmitted to the chassis, in particular the harmonic components at 1x and 2x the rotational speed of the wheel. In the second type of test, the suspension system A Method for Vibration and Harshness Analysis Based on Indoor Testing of Automotive Suspension Systems 2010-01-0639 Published 04/12/2010 M. Gobbi, P. Guarneri, G. Mastinu and G. Rocca Department of Mechanical Engineering, Politecnico di Milano (Technical University), Milano, Italy L. Castignani Ferrari Automobili, Maranello, Italy Copyright © 2010 SAE International SAE Int. J. Mater. Manuf. | Volume 3 | Issue 1 290