Development times have become more important with the evolution of electric vehicles, and prototype development is no exception. This paper presents a simulation method which enables the definition of drivetrain component requirements for an electric race car based on vehicle data and estimated use cases. The simulation method consists of a trajectory simulation, vehicle simulation, and thermal simulation which provide detailed results from multiple aspects of the drivetrain. The results of these simulations can facilitate subsequent decision-making about drivetrain design and provide useful information in early stages of the development, thus speeding up the process.