i'm gonna be the weird guy and say you should get your colsons from battlekits.com
http://www.battlekits.com/robot_whee...th%20Sprockets
i've used these before on non first robots and i highly recommend them.
robutt marketspace has a good selection of colson wheels without hubs or sprockets.
http://www.robotmarketplace.com/prod...on_wheels.html