RFV, as well as all other force variation measurements, can be shown as a complex waveform. This waveform can be expressed according to its harmonics by applying Fourier Transform (FT). FT permits one to parameterize various aspects of the tire dynamic behavior. The first harmonic, expressed as RF1H (radial force first harmonic) describes the force variation magnitude that exerts a pulse into the vehicle one time for each rotation. RF2H expresses the magnitude of the radial force that exerts a pulse twice per revolution, and so on. Often, these harmonics have known causes, and can be used to diagnose production problems. For example, a tire mold installed with 8 segments may thermally deform as to induce an eighth harmonic, so the presence of a high RF8H would point to a mold sector parting problem. RF1H is the primary source of ride disturbances, followed by RF2H. High harmonics are less problematic because the rotating speed of the tire at highway speeds times the harmonic value makes disturbances at such high frequencies that they are damped or overcome by other vehicle dynamic conditions.
