The original BMW hub caps are made of mild steel sheet metal. The paint gets scratched and will easily rust. They also dent easily.
Joe Groeger solved these two problems by making a stainless steel hub cap. It can be painted and appears to be stock. Use the correct paint color and the judges won’t know the difference on your show bike. It is stronger, so resists denting and if the paint gets scratched, it doesn’t rust.
They currently are not in production, but Vech still has a many in stock.
As soon as I can solve a photo issue I will post a photo of this fine product.