Just to start this off here are some common ways to characterize a robots performance:
2. Size (Dimensions)
3. Center of Gravity
5. Maximum ascent and descent angles
6. Tip-over angles
7. Towing capability
8. Power Consumption (idle and in-action)
I am asuming we are talking about sumo robots, so:
1. Make it the maximum allowed. Use a digital scale. Use what ever as weight to get it just right to be admited.
2. A wide robot will turn slow, so make your robot longer, not wider is possible.
3. Keep COG low, something like 2 thirds over the wheels axle and one third on the plowing wedge.
4. You have to figure a torque-speed-friction formula that will keep your wheels spinning when going against a wall, but not verry fast spinning. Someting like one rotation in 2-3 seconds. Use wide wheels, rubber or silicon, something a little softer than hard rubber. If you use neoprene, coat it with silicone.
5. You don't need that in a sumo robot.
6. Same like above.
7. In sumo it's pushing force. That will be figured out in step 4.
8. Power... never calculated it.
That will be from my sumo contests experience, all with Lego robots, some contests using a pure mechanical robot without a microcontroller and some contests going against regular robots (mini sumo). Back with pictures soon.