I agree that it's probably a defect from whoever made the wheels for BMW. But this issue happens across car brands and the dealers or manufacturers very rarely replace wheels on anything with more than maybe 10000 miles on it. Crappy, but it is what it is. Might be easier to just refinish them. Of course that's what BMW wants you to do, but your time investment is your personal equation. Anyway, I hope they do step up for you, but iparaphrasing Grumpy Old Men. "You can hope in one hand and sh*t in the other. See which one fills up first."

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)