Robotic ground vehicles are systems that use gravity and contact forces with the ground to perform motion. In this paper we will focus on n-wheeled vehicles able to perform motion with all the wheels maintaining contact at the same time. The main goal of this work is to establish the implication of the topological architecture of the vehicle mechanism on criteria such as climbing skills, robustness, weight, power consumption, and price. Tools will be provided to help the robot designer to understand the implications of important design parameters like the number of wheels, the vehicle mechanism, and the motorisation of joints on the above criteria. Two examples of innovative locomotion concepts for rough terrain are presented and discussed.