Multibody Dynamic Analysis of an E-Scooter Considering Asymmetric Tire Stiffness, Speed, and Surface Roughness

E-scooters have become a widely adopted form of urban mobility, increasing the need to understand how vibration exposure affects comfort and safety. While most studies have examined the effects of speed, pavement roughness, and overall tire stiffness, none have evaluated how differing stiffness curves between the front and rear wheels influence rider comfort. This article uses real stiffness curves for rigid and inflatable tires at various pressures (30 psi, 60 psi, and rigid) to assess how front–rear stiffness asymmetry affects vibration transmission across speeds (10–20–30 km/h) and two roughness levels (low and high). The analysis, following the standard UNE-ISO 2631-1:2008 and supported by a multiple-regression model (adjusted R² = 93.84%, homoscedastic residuals), shows that speed and roughness dominate the comfort response (98.9%), while tire stiffness offers a secondary (1.1%) but useful tuning parameter, inducing comfort index variations exceeding 14% between front–rear pressure combinations under typical urban conditions (~20 km/h, low roughness). In this case, the most favorable configuration corresponds to inflatable tires with slightly higher front pressure (+2.9–4.35 psi), whereas solid tires consistently yield the poorest comfort. These findings underscore the role of front–rear stiffness management in improving ride quality and provide practical guidance for optimal inflation strategies in urban e-scooters.