I use pololu wheels and hubs, but the original set screws are a complete waste of time. I went down Maplin and bought a box of assorted M3 and M4 screws. I sat with the hubs, wheels, gearboxes and brackets and just tried a selection of screws till it all went together properly and was tight. The screws have a propper head on so you can tighten them up really well with a screwdriver and stop them coming loose. Between fights I'll usually just nip them up. To be honest it's mostly the shaft adapter set screw that comes loose, the bracket and wheel screws are still tight two years on. I can supply up close pictures if it helps. Just let me know what you need. If you wanna share a pit at events for some help you're more than welcome, although I'm not the best builder but not too bad at bodging up to get stuff back in the arena. Makes all the difference when ya robot was hammered n tin snipped in the first place