We switched our robot to the 2012 kit of part wheels and after driving around a bit we had this issue:
http://24.media.tumblr.com/tumblr_m1...s4zo1_1280.jpg
The plastic around the bearing failed and the bearing came loose on the shaft. This was the middle wheel on the standard kit frame, at first we just thought it was a fluke however recently another wheel failed the same way.
So has anyone had this issue? We were thinking about filling the gaps around the bearing with epoxy so they hold up better.