Abstract
Tire vibration modes as a characterization of tire dynamics are used in a broad
range of tire/vehicle system simulations, ranging from low-frequency vehicle handling to
higher frequency structure-borne and air-borne noise simulations. The modal parameters are
used either to define a complete modal tire model or to calibrate parameters of a tire model to
represent the proper dynamic behaviour. This paper presents the experimental modal analysis
of non-rotating radial tires under different boundary conditions. The results are then used to
analyze the influence of tire vibration modes on the structure-borne noise and vibration
characteristics of a vehicle.
Experimental modal analyses are performed on a slick - tire without tread pattern - and on a
commercial tire, both of size 205/55R16. The tire is excited by 2 shakers and the dynamic
responses on the tire and rim are measured in radial, tangential and axial direction with tri-axial
accelerometers. A modal analysis is performed under three different boundary
conditions: free tire, unloaded tire on a fixed hub and loaded tire on a fixed hub. Mode shapes,
resonance frequencies and modal damping are assessed up to 300 Hz. The modal parameters
of the tire under different boundary conditions are analyzed and compared in order to obtain
physical understanding of tire vibration modes. Throughout the whole paper, practical testing
considerations and limitations in accuracy and frequency range are discussed. These
limitations determine the accuracy and performance of tire/vehicle system simulations which
use the experimental modal tire parameters as input data.
Furthermore, the influence of tire vibration modes on the structure-borne noise and vibration
characteristics of a vehicle is discussed. Tests are performed on a smooth road that contains a
pattern of straight curbs. Vibration and noise frequency spectra are measured in the vehicle
interior for different driving speeds and curb dimensions. The vibration and noise spectra of
the curb impact response are analyzed to identify the tire modes that contribute significantly
to the transfer of energy from the tire patch towards the vehicle structure. The results are
compared and discussed in relation to the different driving speeds and curb dimensions.
Keywords: Tire, modal analysis, boundary condition, road test, structure-borne noise