Is the predictability of a rear derailleurs performance more a result of proper setup and maintenance, or is it a testament to the design and engineering of the derailleur itself? Does the comfort we find in a well-functioning derailleur stem from the fact that weve simply become accustomed to its quirks and limitations, or is it a genuine indication of the derailleurs reliability and consistency? In other words, are we giving too much credit to the derailleurs design when, in reality, its the riders attention to detail and maintenance habits that ultimately determine its performance?