[Greg Needel]

i don't think that would fry your speed controllers but here are 2 options for you. what you are talking about is called a coaster and you can buy basically hubs and have them re-spoked for small wheels, this will work but don;t expect to be able to have back wards on your robot because there is no clutch in them that you can engage and disengage.

a better option in my mind is if you need to push the robot around design a quick release somewhere in your drive train and disengage the wheels from the motor. the quickest way i can think of is a decent cotter pin that you can pull in and out.

but even better then that is make a cart. if you design a light cart there is no reason you should push your robot around, even though i doubt that spinning the motor back wards would cause enough current to cause any damage.