Indexed shifting movement is measured as a precise distance the derailleur travels to reach the next gear. Which component movement achieves this?

• A. The derailleur moves a random distance
• B. The derailleur moves a fixed distance only when pedaling
• C. The derailleur moves a precise, preset distance
• D. The derailleur remains stationary and only the chain moves

Answer: (C)

In indexed shifting, the key idea is that the derailleur must move a precise, preset distance with each shift. The shifter pulls the cable a specific amount, and the derailleur is calibrated so that this exact cable pull translates into a fixed travel that positions the chain on the next cog. That controlled, repeatable movement is what makes shifts land on the intended gear every time, regardless of how hard you’re pedaling or other variables.

If the derailleur moved a random amount, or only moved when you’re pedaling, or if the chain moved while the derailleur stayed put, the chain wouldn’t align with the correct gear. The entire reliability of indexed shifts rests on the derailleur moving a precise, preset distance.