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Increasing the stability of a motorcycle requires an understanding of the optimal conditions of the tyre. The inflation pressure is one of the main parameters that directly affects the tyre properties, which in turn influences motorcycle stability and safety. This paper focuses on the effect of the inflation pressure of the tested tyres on motorcycle weave stability. Experimental data are collected from tests carried out in straight running at constant speed. The data analysis is based on stochastic subspace identification methods. Simulations are performed using an advanced motorcycle multi-body code with parameters measured from the tested vehicle. Finally, the comparison between simulations and experimental tests is discussed. The research results show an agreement between experimental tests and simulations where weave stability increases with inflation pressure for the specified range of tyre pressure. [ABSTRACT FROM PUBLISHER]

It is well known that front fork flexibility may have a significant effect on motorcycle stability. This work addresses the problem of developing lumped element models of the front fork from experimental results. The front forks of an enduro motorcycle and of a super sport motorcycle are characterized performing static, dynamic and modal tests by means of specific testing equipment. The concept of wheel twisting axis is proposed to characterize static and dynamic deformability of the front fork. Modal analysis results show the presence of two important modes of vibration of the front assembly in the low frequency range: the lateral mode and the longitudinal mode. Different lumped models are discussed and a new model that takes into account information obtained from static and dynamic tests is proposed. Simulations are carried out by means of a multibody code and show the effect of the front assembly deformability on the weave and wobble vibration modes. [ABSTRACT FROM AUTHOR]

Motorcycle dynamics is characterised by the presence of modes of vibration that may become unstable and lead to dangerous conditions. In particular, the weave mode shows large yaw and roll oscillations of the rear frame and out of phase oscillations of the front frame about the steer axis. The presence of the rider influences the modes of vibration, since the mass, stiffness and damping of limbs modify the dynamic properties of the system; moreover, at low frequency the rider can control oscillations. There are few experimental results dealing with the response of the rider in the presence of large oscillations of the motorcycle. This lack is due to the difficulty of carrying out measurements on the road and of reproducing the phenomena in the laboratory. This paper deals with a research programme aimed at measuring the oscillations of the rider's body on a running motorcycle in the presence of weave. First, testing equipment is presented. It includes a special measurement device that is able to measure the relative motion between the rider and the motorcycle. Then the road tests carried out at increasing speeds (from 160 to 210 km/h) are described and discussed. Best-fitting methods are used for identifying the main features of measured vibrations in terms of natural frequencies, damping ratios and modal shapes. The last section deals with the comparison between measured and simulated response of the motorcycle–rider system in weave conditions; good agreement was found. [ABSTRACT FROM PUBLISHER]

The behaviour of a motorcycle on the road is largely governed by tyre properties. This paper presents experimental and numerical analyses dealing with the influence of tyre properties on the stability of weave and wobble in straight running. The final goal is to find optimal sets of tyre properties that improve the stability of a motorcycle. The investigation is based on road tests carried out on a sport-touring motorcycle equipped with sensors. Three sets of tyres are tested at different speeds in the presence of weave and wobble. The analysis of telemetry data highlights significant differences in the trends of frequency and damping of weave and wobble against speed. The experimental analysis is integrated by a parametric numerical analysis. Tyre properties are varied according to the design of experiments method, in order to highlight the single effects on stability of lateral and cornering coefficient of front and rear tyres. [ABSTRACT FROM PUBLISHER]

Despite the importance of rider passive response to the lateral dynamics of motorcycles, there is very little literature on the subject. Even more uncommon are works that consider rider passive steering impedance and its effect on motorcycle stability. Moreover, until this time, there have been no published studies on steering impedance that include correlation to on-road motorcycle stability testing. This paper explores these topics using an advanced motorcycle simulation model which includes rider torso and steering impedance values derived from experimental characterisation and anthropometric modelling. A novel method for quantitatively evaluating on-road stability is discussed and utilised to compare the simulation results to on-road weave stability testing for two different riders in the ‘hands-off’ and ‘hands-on’ the handlebars conditions. Good correlation is achieved between simulation and test indicating stability differences between riders and highlighting hands-off/on effects. [ABSTRACT FROM AUTHOR]

An approach of analysing the stability and bifurcations of a multibody system previously developed is applied to a model for a modern motorcycle. The model includes a suspension system and aerodynamic drag. Conditions of running straight ahead on a level road at a constant forward speed and cornering in a curve with constant radius are analysed. The drag force, in combination with the suspension system, gives an increased region of stability, and the suspension system in itself prevents the loss of contact between tyres and road in the resulting periodic solutions after the stability limit has been reached. [ABSTRACT FROM AUTHOR]