I was wondering how much reduction should be applied to cim motors in a swerve application. We are thinking about using two cim motors per side, so that the swerve can switch to tank and swerve. Both the toughbox from AM and the Banebots P80 planetary look promising. What kind of reduction should be applied to a coax-swerve in a carpet setting. Within the module, we have a ratio of 1:2.75 so we get 2.75 turns out of the wheel for every turn of the top shaft. I guess it finally does come down to the type of the game, whether we need to push people around or we need complete speed, but what would be a good ratio for an off season project?
First question: How large are your wheels?
Second question: Well, how fast do you want to go? 
For demo purposes lower speeds offer better controllability (and therefore safety) and battery life (less current draw under normal loads).
We are using the 4" Performance Wheels from AM. I guess we would like to keep the speed open ended. Are the Banebot’s P80s like the GEM 500s where you can add additional stages?
Here is a picture to help explain:
http://bayimg.com/image/iaemmaace.jpg
No, you can’t stack P80s (the input shaft is 8mm while the output is 1/2" keyed). But you shouldn’t need to anyway. If you run from the Toughbox (12.75:1) to your swerve module without any sprocket reduction, you are looking at about a 4.6:1 reduction (12.75/2.75). That’s a little fast, giving you about 15fps top speed. If you use the driving sprocket on top of the module to reduce by another 2:1, you’re in a good single speed ballpark (~7.5 fps). You can further tweak the ratio by playing with the exact sprocket ratio - something that is much quicker to change than your gearbox reduction.
Also, standard swerve disclaimer: you might want to think about ways to support your modules closer to the bottom. The side loads you get on the wheel when pushing or turning at high speeds, coupled with the effective moment arm created by the height of your module, can put a lot of torque on the joint with the chassis.