[Grommit]

I'd like to point out that the 12" wheels are actually 12.5" wheels, which makes a slight difference. But more importantly, it requires a very low center of mass to drive one of these things. I watched Kehillah Jewish High School, Team 1043, with Patrick as driver (over two years of experience), in practice, and even he had problems with the robot tipping over. The robot had a large arm mounted upon it to hang, and it wasn't particularly heavy, but consider the following:

Diameter 12.5" implies a maximum wheel base of under 24 inches, probably 20 after the protection in the front. Under these rather optimal conditions, with one wheel up on the step and the other down, we have an angle of nearly 18 degrees. With a center of mass that is high enough, the momentumof the base might flip you over before your other wheel reaches the step.