Identification of the characteristics of motorcycle and scooter tyres in the presence of large variations in inflation pressure

Abstract

Stability and safety of road vehicles are largely affected by tyre properties. Single-track vehicles are characterised by weakly damped modes of vibration (weave and wobble) and therefore this phenomenon is even more important. This article focuses on the study of both steady-state and transient properties of motorcycle and scooter tyres in the presence of very low and very high inflation pressures. The steady-state properties are defined as lateral forces (side-slip and camber forces) and yaw torques (self-aligning and twisting). The transient properties are described in terms of relaxation length, which represents the distance needed to reach a certain percentage of the steady-state value of the tyre force. Experimental tests are carried out on a specific rotating disk machine. Three sets of tyres are analysed. Steady-state properties are measured by increasing step by step the values of camber and side-slip angles. Transient properties are studied carrying out tests with harmonic sideslip excitation and measuring the phase lag between the excitation (input) and the tyre force (output). Experimental results show important variations in tyre properties with inflation pressure with general trends of all the tested tyres and particular features related to the tyre’s geometry. After the analysis and discussion of experimental results, the measured data are fitted by means of a specific version of the Magic Formula. The dependence of the Magic Formula’s coefficients on inflation pressure is analysed and interpolation curves are given

Identification of the Mechanical Properties of Tires for Wheelchair Simulation

“…6.2) increases (in modulus) when inflation pressure decreases, probably because the contact patch becomes larger. This result is in agreement with the ones obtained measuring bicycle and motorcycle tires [11,12]. Coming to camber force, Fig.…”

“…(6.1). This trend agrees with the ones measured in bicycle tires [12] and the ones measured in motorcycle and scooter tires, which sometimes also show a saturation at high pressure [11]. Self aligning torque ( Fig.…”

“…Coming to camber force, Fig. (6.3) shows that camber force generated by tire A is not influenced by inflation pressure, like in bicycle tires [12]; whereas camber force generated by tire B tends to increase if inflation pressure decreases, like in many motorcycle tires [11].…”

“…(7). In wheelchair tires, like in bicycle [12] and motorcycle tires [11], when vertical load increases lateral forces do not increase proportionally, because normalized lateral forces decrease when vertical load increases. This effect is particularly important for side slip force ( Fig.…”

“…The first phase of the research focused on the measurement of tire properties by means of the tire testing machine of Padova University, which has been used in the past for identifying the mechanical properties of motorcycle and scooter tires [10,11] as well as bicycle tires in a more recent study [12]. The behavior of wheelchair tires under different working conditions has been investigated.…”