Obviously not using my brain - I went for four weeks without cleaning my wheels (17" cross spokes). Now I've got some tiny black specks on my wheels. It seems that I can remove most of them with some good fingernail work, but that would take over an hour per wheel. I tried a "scruffy" sponge (the softer kind) to no avail. I did not want to try anything harsher.
Any advice on how to get the black off?