Derailleur Tuning

Derailleur Tuning: Achieve Perfect Shifting Every Time

A properly tuned derailleur delivers crisp, reliable shifts through every gear. Whether your bike shifts poorly out of the box or has developed problems over time, understanding derailleur adjustment transforms frustrating rides into smooth sailing.

Understanding How Derailleurs Work

Derailleurs move the chain between gears using three key adjustments:

• Limit screws: Prevent chain from going too far inward or outward
• Cable tension: Controls precise positioning at each gear
• B-tension: Sets gap between guide pulley and cassette

When to Tune Your Derailleur

• Shifts are hesitant or require multiple lever clicks
• Chain skips or jumps between gears
• Noise from drivetrain that changes with gear selection
• Chain falls off cassette at either end
• After cable replacement or crash
• Seasonal maintenance or when shifting feels off

Tools Required

• Phillips or flathead screwdriver (for limit screws)
• 5mm hex wrench (for cable anchor)
• Cable cutters and end caps
• Work stand or way to lift rear wheel

Step 1: Check the Basics First

Before adjusting, verify these fundamentals:

1. Derailleur hanger alignment: Bent hangers cause most shifting problems. Check straightness with alignment gauge or professional service.
2. Cable condition: Frayed or corroded cables prevent smooth operation.
3. Housing condition: Kinked or compressed housing creates shifting issues.
4. Chain wear: Stretched chains skip on gears regardless of adjustment.

Step 2: Set the High Limit Screw

The high limit (marked H) prevents chain from falling off the smallest cog:

1. Shift to smallest cog and largest chainring
2. Disconnect cable from derailleur or release all tension
3. Without cable tension, derailleur should rest at smallest cog
4. Adjust H screw until upper pulley aligns directly below smallest cog
5. Too far out risks chain falling off; too far in prevents reaching top gear

Step 3: Set the Low Limit Screw

The low limit (marked L) prevents chain from going into spokes:

1. With cable still loose, manually push derailleur toward wheel
2. Adjust L screw so derailleur stops with pulley below largest cog
3. Verify derailleur cannot push chain past largest cog
4. This is a critical safety adjustment – chain in spokes causes crashes

Step 4: Set Cable Tension

This determines precise gear indexing:

1. With limit screws set, reconnect cable
2. Pull cable taut and tighten anchor bolt
3. Shift to second smallest cog
4. While pedaling, listen for noise from chain wanting to shift
5. Adjust barrel adjuster: counterclockwise adds tension (pulls toward larger cogs), clockwise reduces tension
6. Goal is silent running in each gear with immediate response to shift lever

Step 5: Fine Tune Through All Gears

1. Shift through entire cassette in both directions
2. Note any gears that hesitate or require extra clicks
3. Adjust barrel adjuster in quarter-turn increments
4. If upshifts are slow, add tension (counterclockwise)
5. If downshifts are slow, reduce tension (clockwise)
6. Repeat until shifts are crisp throughout range

Step 6: Set B-Tension

This controls the gap between guide pulley and cassette:

1. Shift to largest cog
2. Look at gap between upper pulley and cog teeth
3. Gap should be approximately 5-6mm (or per manufacturer spec)
4. Adjust B-screw to increase or decrease gap
5. Too close causes noise; too far causes slow shifting to large cogs

Front Derailleur Basics

Front derailleurs follow similar principles:

1. Height: Bottom of cage should clear largest chainring by 1-3mm
2. Angle: Cage should be parallel to chainrings when viewed from above
3. Limit screws: Prevent chain from falling off inside or outside
4. Cable tension: Enables precise shifts between rings

Troubleshooting Common Problems

Chain skips under power:

• Worn chain or cassette
• Insufficient cable tension
• Bent derailleur hanger

Cannot reach largest cog:

• L limit screw too tight
• Insufficient cable tension
• Cable stretch or friction

Chain falls off smallest cog:

• H limit screw needs adjustment
• Bent derailleur hanger pulling outward

Noisy in certain gears:

• Fine-tune cable tension
• Check for chain wear
• Verify pulley wheels spin freely

Maintaining Your Tune

• Regular cleaning: Grit in derailleur pivots causes sluggish shifting
• Cable lubrication: Dry cables add friction and slow response
• Check hangers: Inspect after any crash or impact
• Replace cables annually: Preventive maintenance beats trailside repairs

Derailleur tuning requires patience and systematic approach. Work through adjustments in order, make small changes, and test thoroughly. With practice, you will be able to tune any derailleur to shift perfectly.