For a racing wheel you can't beat the SSR Competition (C-RS). They are light and strong (semi-solid forged). The 18" x 9.5"s weigh just 19.6 lbs according to tire rack:
I have had these for my E36 M3 track car for 4 years and they've been great. I think on the E90/92 M3 you can run 9.5" all around (35 mm offset). What do you think Enigma?