Just remembered something that may help. Not googled yet, but I seem to recall that Audi had some problems with the original 19" rims fitted to the original RS4 - which came out in what 1999/2000? I only remember a short piece being reported in Autocar at the time. It maybe worth trawling the Audi forums to find out more. The bottom line was that on UK roads, the 19" rims were buckling (and maybe cracking?) - a problem not seen in the domestic market I don't think. Cars with the problem did get to owners I think.
Edit: looks slightly different issue - they were too soft....
...still lots of precedent, with Audi still replacing the defective wheels as goodwill in 2008.