Abstract: Battlefield mobility is one of the fundamental requirements of tracked military vehicles. The suspension provides the necessary ride, handling, and traction for the vehicle when traversing over either paved roads or on unprepared terrain. The Hydro-gas Suspension Unit (HSU) is one current state-of-the-art suspension technology with a huge potential for improvement in the future. In this work a mathematical model is developed and simulated using Matlab and Simulink. The model incorporates the compressibility of the fluid and expansion of other components using an effective bulk modulus and the damper valve characteristics. A novel method of modelling the flow through the damper valve using a lookup table is presented to overcome a problem with algebraic loops. Results from the model are discussed for different damper valve characteristics and input frequencies. The HSU model is incorporated into a simulation of a six-wheel station tracked vehicle having eight degrees of freedom, in order to study the ride quality of the vehicle and to propose a method for selecting the damper valve characteristics.