OK, they're not really alloy. Although you could cast them out of shiny metal if you wanted. I'm going to have a go with some metallic filament I've got lying around.
Anyhoo, I've spent some time today improving the Hull Pixelbot wheels. They've been simple disks for too long. They now have a specially designed rim which turns a simple elastic band into a workable tyre (and the band doesn't seem to come off) and the rim is actually narrower than the wheel. And, the wheel now has holes in for lower weight, a better 0-60 time and faster printing.
I've just to do one final test on the finished design and then I'll put them on GitHub.