An understanding of the flow around a tire in contact with the ground is important for when designing a fuel efficient tire as aerodynamic drag accounts for about one third of an entire vehicle’s rolling loss [1]. Recently, non-pneumatic tires (NPTs) have drawn attention mainly due to their low rolling resistance associated with the use of low viscoelastic materials in their construction. However, an NPT’s fuel efficiency should be re-evaluated in terms of aerodynamic drag: discrete flexible spokes in an NPT may cause more aerodynamic drag, resulting in greater rolling resistance. In this study, the aerodynamic flow around an NPT in contact with the ground is investigated for i) stationary and ii) rotating cases using the Reynolds-Averaged Navier-Stokes (RANS) method. The NPT has a more complex flow and a higher drag force than does the pneumatic counterpart.

With an increased interest in a non-pneumatic tire (NPT) and its possible performance on safety in driving and low rolling resistance, extensive research on mechanical properties including dynamic characteristics are required to explore for the commercialization of NPTs. In this study, we explore the dynamic characteristics of NPTs with flexible hexagonal lattice spokes. A steady state vibration characteristic of NPTs is investigated with a series of load carrying capability and rolling speed for two hexagonal spokes using a commercial finite element code, ABAQUS. The obtained vibration characteristics are compared with those of conventional pneumatic tires, which are available in the literature.

Recently, the development of non-pneumatic tires (NPT) such as the Michelin Tweel is receiving increased attention due to potential advantages over pneumatic tires, including characteristics of rolling resistance (RR). This study focuses on the design of a NPT based on properties of vertical stiffness and rolling energy loss. Using a finite element (FE) model, a parametric study is conducted to study the effect on vertical stiffness and RR response considering two design variables; (a) thickness of the spokes, and, (b) the shear band thickness of the NPT. Using the two geometric variables, a design of experiments (DOE) is performed to study the effect on both RR and vertical displacement. Results from the DOE are used to create response surface models (RSM) for both the objective function (minimal RR) and a constraint on vertical deflection. The analytical RSM function is optimized for minimizing the rolling loss subjected to the given constraint. In addition a design sensitivity study is performed to evaluate the influence of the design variables on the output response. Results indicate that both variables have significant effect on RR, with the shear band thickness having the greater effect.