Adjusting Limit Screws

The limit screws on your derailleur control its range of movement and are essential for ensuring smooth, precise shifting on your bike. Both high and low limit screws regulate the derailleur's lateral movement, preventing it from moving too far inward or outward on the cassette, which could cause issues such as chain skipping, noise, or even chain derailment. Proper adjustment of these screws is crucial for optimal performance, so here’s an in-depth guide to help you adjust your derailleur’s limit screws with precision.

High Limit Screw Adjustment (H-Screw)

1. Identify the High Limit Screw:
   Find the screw labeled “H” on the derailleur, which controls the position of the derailleur in relation to the smallest cog (high gear) on your cassette.

2. Prepare for Adjustment:
   Using a Phillips head screwdriver, begin by turning the high limit screw to tighten or loosen it. Tightening the screw moves the derailleur inward, while loosening it pushes the derailleur outward.

3. Set the Derailleur Position:
   Shift the bike to the smallest cog (highest gear). Adjust the high limit screw until the derailleur aligns perfectly with the smallest cog, ensuring that the chain runs smoothly without rubbing or interference from the frame or spokes.

4. Test the Shifting:
   Pedal the bike and shift between the smallest cog (high gear) and the second smallest cog (second gear). The chain should shift smoothly without hesitation.
   While the bike is in the smallest cog, ensure that the derailleur does not move any further toward the frame when you shift to a lower gear. You should feel consistent resistance in the shifter and no additional movement toward the frame.

Low Limit Screw Adjustment (L-Screw)

1. Identify the Low Limit Screw:
   Locate the low limit screw labeled “L,” which controls the position of the derailleur in relation to the largest cog (low gear) on your cassette.

2. Set the Derailleur Position:
   Shift the bike to the largest cog (lowest gear). Tighten or loosen the low limit screw to adjust the derailleur's position. Tightening moves the derailleur toward the frame, while loosening it pushes the derailleur outward, closer to the wheel spokes.

3. Test the Shifting:
   After adjusting, pedal the bike and shift between the largest cog (easiest gear) and the second largest cog (second easiest gear). The chain should shift smoothly between these two gears without hesitation.
   Make sure that, when in the largest cog, the derailleur does not move further outward toward the wheel. If the derailleur moves too far out, it can cause the chain to drop off the cassette.

4. Ensure Proper Alignment:
   Double-check that the derailleur is correctly aligned with the largest cog and does not shift past it toward the wheel when you press the thumb lever. Any lateral movement toward the wheel could cause the chain to derail off the largest cog.

Fine-Tuning the Adjustments

1. Smooth out Hesitation:
   If you notice that the chain hesitates or struggles to shift into the largest or smallest cog, fine-tune your limit screws.
   Start by adjusting the low limit screw (L) in quarter-turn increments to refine the position of the derailleur. Test the shifting after each adjustment.

2. Verify Shifting Performance:
   Shift through all gears, confirming smooth and accurate transitions between each. The derailleur should stay within its set limits and not cause any chain skipping, grinding, or slipping.

Verification of Proper Adjustment

1. Check High and Low Limits:
   Confirm that the derailleur aligns properly with both the smallest and largest cogs in the cassette, with no excessive lateral movement.

2. Test All Gears:
   Shift through all gears (from the smallest to the largest cog and vice versa) to ensure smooth transitions. The derailleur should not exceed the limits set by the high and low limit screws, and there should be no rubbing or chain drops.

Final Thoughts:

With the high and low limit screws properly adjusted, your derailleur will shift smoothly, quietly, and efficiently during rides. These small adjustments ensure that the derailleur stays within the cassette’s limits, preventing chain derailment and ensuring you experience the best performance from your bike.

Maintenance and Further Adjustments

Keep in mind that as your bike undergoes wear and tear, regular checks and minor fine-tuning of the limit screws are necessary to maintain smooth shifting performance. 

By following these steps carefully, you’ll ensure long-lasting, efficient shifting and a more enjoyable ride.