This paper focuses on the bogie-carbody nonlinear dynamic interaction of a Shinkansen high-speed rail vehicle. The Euler-Bernoulli beam model is used to simulate vertical elastic vibrations of the carbody. As a novelty, the traction rod that connects the bogie frame and the carbody is considered a nonlinear element. The equivalent linearization method is used to analyze the nonlinear vehicle system in the frequency domain. The analytical spectrum solution was compared with the measured data from the running test and the numerical solution in the time domain. When the dynamic interaction due to the carbody’s flexibility is considered as nonlinear rather than linear, the maximum amplitude of the bounce acceleration relevant to the first bending mode increases by 38.2 percent at a travel speed of 300 km/h. Ride comfort improvement can be achieved with the inclusion of the nonlinear interaction. It is also feasible to manipulate the vehicle’s ride comfort by altering its bogie-base The authors gratefully acknowledge precious remarks and valuable propositions from Professor Takahiro Tomioka during this research. The third author would also like to acknowledge the funds provided by the NVTRail project (Noise and Vibrations induced by railway traffic in tunnels: an integrated approach), funded by FEDER funds through COMPETE2020 and by national funds (PIDDAC) through FCT/MCTES, with grant reference POCI-01-0145-FEDER-029577; and by the VIBWAY project (Fast computational tool for railwayinduced vibrations and re-radiated noise assessment), with reference RTI2018-096819-B-I00, supported by the Ministerio de Ciencia e Innovación, Retos de Investigación 2018