What are the two small derailleur screws used for?

• A. They are used to adjust chain tension
• B. They are stop limit screws to set maximum excursion
• C. They mount the derailleur to the frame
• D. They adjust the pulley wheel alignment

Answer: (B)

Two small screws on the derailleur are the travel limits. They act as stop limit screws that set how far the derailleur can move toward the smallest and largest gears. By adjusting them, you pin the maximum inward and outward sweep of the derailleur so the chain can’t overshoot the range and drop off either end.

These screws are usually labeled for the inner and outer limits, and you adjust them with a small screwdriver. Turning a limit screw tightens that end of travel, while backing it out loosens it, allowing more movement. The goal is to have the derailleur line up so the chain sits on the correct sprocket when you shift, without rubbing on the frame or trying to go past the largest or smallest gear.

They aren’t used to set chain tension, attach the derailleur to the frame, or align the pulleys. Those tasks involve mounting hardware, the tension mechanism, and pulley alignment or B-tension adjustments, respectively.