My previous job I worked at a game company where we were creating a lunar racing game. It never got completed for a number of mostly managerial/business reasons but we got as far as playable levels. Because our mandate was to make something semi-educational we attempted to make the physics as real as possible and used NASA terrain data to create the courses.
What we learned early on was that ground based vehicles are basically uncontrollable above 20-30kph because their wheels were so infrequently on the ground. Ultimately we wound up with a series of control thrusters (similar to Apollo or the shuttle) mounted to all the vehicles:
This not only keep the vehicle on the surface but allowed for some seriously acrobatic hoonage.
Too bad we never got to finish it...it was pretty fun.
More here: [www.virtueplay.com]
Isn't the point of this story that they don't?