I bought some 04 wrx rims and before putting them on my car I decided to give them a good clean as there was alot of break dust on from the previous owner.

I have used several wheel/tyre cleaning products to get most of it off, however on the back of the rim (can see in the pic below) there is still some stubborn marks that do not come off.





Any ideas/products that will get this off?

Thanks
Jake