[John]

If you don't gear down the CIM motors at all, and you used six inch wheels, you would be geared for:
5310 rpm * (6inch * pi /revolution) * (1foot/12inch) * (1minute/60seconds) =
139 feet per second

Typically, a ~150 lb FIRST robot is geared for no more than about 16 feet per second, and usually less. Anything much higher draws too much current, and heats up the motors too fast.