It's the front wheel on the side with two wheels (plus the little one inbetween), the other side just has one wheel. My pool supply store told me it was because the threads where the screws screw into have warn off and I need a new sweeper. I find that hard to believe. Does anyone know a work around. My first thought was to put a nut on the other side, but it's inside the bottom and there's no access. Other ideas? Some kind of glue????