Derailleur adjustment fixes poor shifting performance. Properly indexed gears shift smoothly without chain dropping or skipping.
Quick Answer: Set limit screws to prevent chain dropping, adjust cable tension for crisp shifts across the cassette, and fine-tune B-screw for proper cage clearance. Start with low limit (L) screw, then high limit (H), then cable tension.
Limit Screw Adjustment
Shift to the largest cog (easiest gear). Adjust the L screw until the upper pulley aligns directly below the largest cog. Shift to the smallest cog and adjust the H screw for alignment with the smallest cog.
Limit screws prevent the chain from shifting off the cassette. Too loose allows chain drops, too tight prevents shifting to extreme gears.
Cable Tension Indexing
Shift to the second-smallest cog. If the chain hesitates to shift up to larger cogs, increase tension by turning the barrel adjuster counterclockwise. If it hesitates shifting down, decrease tension by turning clockwise.
Make quarter-turn adjustments and test shifting through the entire range. Perfect indexing produces immediate, quiet shifts in both directions.
B-Screw Adjustment
The B-screw (angle screw) sets the gap between the upper pulley and largest cog. This gap should measure 5-6mm. Adjust the B-screw to achieve proper clearance—too close causes noise, too far reduces shifting performance.
