[lukevanoort]

Using free seed, if you put a 12 tooth gear on a CIM then to a 36 tooth gear for a 4:1 reduction, you'd get 1327.5 rpms. Put a 15 tooth gear on that shaft which drive the wheels which are using another 36 tooth gear you get to 553.125 rpms. That translates to roughly 9.65 ft/s. Use 95% efficency for each gearing, that goes to 8.71 ft/s realistically. A respectible speed that is, IMHO, a good middle ground speed. Hope tht helped.

BTW: Those are commonly available gear sizes, so its a realistic gearing