[JesseK]

We use lock nuts in all of ours, and haven't had a problem. We had little kids driving on our 6" Plaction wheels off and on for ~12 hours overall at the 2010 Science & Engineering Festival. They held up fine, though granted they weren't being banged over a bump there at the S&EF. Last year's 4" Plaction wheels were slammed from forward to reverse more times than I know, and they also engaged in a few high speed impacts too. They're still fine after 3 regular and 2 offseason competitions. We're using KOP wheels for 2012, the hubs of which look like identical plastic to the Plaction wheels. We've banged them around on the ramp a bit, but we'll see after competition season.