I keep reading over and over, where people post about their derailleur pulleys being worn. The typical response on this forum, is..."if it is still shifting properly, just leave them alone." As someone who makes his living working on mechanical things, I am confused by this repeated statement.
It flies in the face of preventative maintenance and sounds like strange advice. Yet it is prescribed so often that I am inclined to believe there is some truth to it. So what is the purpose of having derailleur "teeth" cut into derailleur pulleys?
I'm not trying to start a huge debate, i'm simply asking if anyone KNOWS why they are there. Why aren't the pulleys round, with no teeth?