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Wheel out of round, which has a significant influence on the ride comfort of vehicles, is very difficult to detect, especially for vehicles with rubber tires like a monorail. The prominent feature of wheel eccentricity caused by wheel out of round is that there will be a dominant frequency of the vehicle acceleration that varies with the speed of the vehicle, while the wavelengthes are all equal to the wheel circumference. By studying the experimental results of Chongqing straddle monorail, an indirect detection method of the wheel out of round is put forward. Then a simulation model of the monorail vehicle under the influence of the wheel out of round is established. The numerical analysis and experimental results lead to that the main reason for the abnormal vibration of the vehicle is the wheel out of round. Through the analysis of the vertical dynamic equation of the monorail system, all other factors that may affect the dominant frequency of vehicle vibration are analyzed. Finally, it is concluded this abnormal vibration caused by wheel out of round can only be reduced by increasing the vertical stiffness of the air spring and car body mass other than changing wheels.

Analysis of the Chongqing monorail shows that there is no relationship between wheel wear and radial force, which means the radial force cannot be used to evaluate the wheel wear of monorail. Due to the same physical significance of the Schallamach tire wear model for automobiles, the wear index of railway wheels, which represents the creep power of unit wheel–rail contact area, is proved to be effective in evaluating the wheel wear of railway vehicles, automobiles, and vehicles with both properties, namely, monorail. Parameters of Chongqing monorail, modified through genetic algorithm, are used to build the model of the articulated monorail. Through co-simulation of the MATLAB and UM software, the wheel wears of two types of articulated monorail are calculated. For both types of monorails, correlation analysis shows that the variation of driving wheel and guide wheel wear of the inner bogies with the track curvature radius are roughly the same. The variation of the wheel wears in the two end bogies is a little different from that of the inner bogies. Comparison indicates that the wheels of the bolster type monorail wear more than that of the non-bolster type. Regardless of the monorail type, the wheels in the inner bogies wear more.