hookooekoo
Senior Retro Guru
One of my friends had one of the rubber tube and wire versions back in the late 80s. He had it set up to permanently drag gently against the tyre. I asked him about it once, and had a good look at it. Over time the wire slowly wears away. As the wire wears towards a semi-circular cross section, I'd guess if gets more and more effective at lifting out small particles of glass and flint.whereas the others are periodically pushed onto the tyre by the rider