It's not road grime or chain throw off, it's tire rubber!!!!
I did see someone else mention this when they used a fairly harsh cleaner to do the rims. Personally I've been using either Spirit Bike Cleaner or McGuire's waterless cleaner with wax and so far no paint residue.Has anyone experienced some of the yellow from the rim on your cleaning rag? I did a nice deep clean on the rear this weekend and was kind of shocked to see yellow on my rag.