Shimano Derailleur Adjustment and Fine-Tuning Guides

How to fix a Shimano derailleur that won’t shift.

Check the Cable Tension 

• Symptom: If the derailleur doesn’t move or shifts poorly, the cable tension may be too loose or too tight.
• Fix: Use the barrel adjuster (located near the shifter or derailleur) to fine-tune the tension:
  • Turn the barrel adjuster counterclockwise to increase cable tension (if it’s too loose).
  • Turn it clockwise to reduce tension (if it’s too tight).

Inspect and Lubricate the Cables

• Symptom: If the derailleur responds slowly or not at all, dirty or corroded cables could be causing the issue.
• Fix:
  • Check the cables for rust, dirt, or fraying.
  • Lubricate the cable inside the housing or, if the cable is damaged, replace it.
  • Reinsert and properly secure the cable.

Adjust the Limit Screws

• Symptom: The derailleur overshifts or undershifts, failing to move across the full range of gears.
• Fix: Adjust the limit screws:
  • H-screw (high limit) controls the movement toward the smallest cog. Adjust it to prevent the derailleur from moving too far outward.
  • L-screw (low limit) controls the movement toward the largest cog. Adjust it to prevent the derailleur from moving too far inward.

Check the Derailleur Hanger Alignment

• Symptom: If the derailleur seems misaligned or skips gears, the hanger might be bent.
• Fix: Visually inspect the derailleur hanger and, if necessary, use a derailleur hanger alignment tool to straighten it or have it replaced if it's severely bent.

Inspect the Derailleur for Damage

• Symptom: If the derailleur is not moving at all or is physically obstructed, it could be damaged.
• Fix: Check for bent derailleur arms, broken jockey wheels, or loose components. If damaged, parts of the derailleur may need replacement.

Adjust the B-Screw

• Symptom: Shifting is slow or unresponsive, particularly in the largest cogs.
• Fix: The B-screw adjusts the distance between the derailleur’s upper pulley and the cassette. Turn the screw to increase or decrease the gap for smoother shifting.

Check the Chain Condition

• Symptom: A worn or stretched chain can cause poor shifting performance.
• Fix: Inspect the chain for wear and replace it if needed. Ensure the chain is properly lubricated and the correct length.

Test the Shifter

• Symptom: If the derailleur doesn’t move when the shifter is engaged, the shifter itself may be faulty.
• Fix: Check if the shifter is functioning properly by pulling the cable manually. If the shifter isn’t releasing or pulling the cable, it may need servicing or replacement.

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Common mistakes when adjusting a rear derailleur.

Incorrect Cable Tension

• Mistake: Either setting the cable tension too loose or too tight.
• Effect: Loose tension can cause sluggish or missed shifts, while overly tight tension can result in overshifting or skipping gears.
• Solution: Fine-tune the cable tension using the barrel adjuster while shifting through the gears to find the correct balance.

Misadjusting Limit Screws

• Mistake: Improperly setting the high and low limit screws.
• Effect: If the high limit screw is too loose, the chain can overshoot the smallest cog and fall off. If the low limit screw is set incorrectly, the chain may fall into the spokes or not reach the largest cog.
• Solution: Set the high and low limit screws carefully, ensuring the derailleur stays within the cassette’s range without going too far.

Skipping B-Screw Adjustment

• Mistake: Ignoring the B-screw, which adjusts the gap between the top pulley and the cassette.
• Effect: Too much or too little gap can cause poor shifting, especially in the larger gears.
• Solution: Adjust the B-screw to maintain the proper distance (typically a few millimeters) between the top pulley and the largest cog.

Forgetting to Check the Derailleur Hanger

• Mistake: Not checking if the derailleur hanger is bent.
• Effect: A bent hanger will cause poor alignment and inaccurate shifting, no matter how well the derailleur is adjusted.
• Solution: Always check the hanger’s alignment, and if it’s bent, use a hanger alignment tool or replace it before adjusting the derailleur.

Not Releasing the Shifter While Adjusting

• Mistake: Forgetting to fully release the shifter to its resting position (smallest cog) before making cable tension adjustments.
• Effect: This can result in improper adjustments, leading to poor shifting performance.
• Solution: Ensure the shifter is in the lowest gear (smallest cog) before adjusting the cable tension.

Adjusting with a Dirty or Worn Chain

• Mistake: Adjusting the derailleur with a worn-out or dirty chain.
• Effect: A stretched or dirty chain can cause poor shifting regardless of how well the derailleur is adjusted.
• Solution: Clean the chain and drivetrain before adjusting, and replace the chain if it’s worn.

Overlooking the Condition of the Cables

• Mistake: Ignoring frayed, stretched, or dirty derailleur cables.
• Effect: Worn or dirty cables can prevent smooth shifting, even if the derailleur is adjusted properly.
• Solution: Inspect and replace cables or housings if necessary before adjusting the derailleur.

Not Properly Aligning the Derailleur Cage

• Mistake: The derailleur cage might be misaligned, either from a bent hanger or general wear.
• Effect: Misalignment can prevent the derailleur from smoothly guiding the chain, causing poor shifting and chain drops.
• Solution: Ensure the cage is straight and aligned before making adjustments.

Not Testing Under Load

• Mistake: Adjusting the derailleur without testing it while pedaling under load.
• Effect: Adjustments that seem fine when the electric bike is stationary may not perform well while riding.
• Solution: Test the gears under normal riding conditions, ensuring smooth shifting across the entire cassette.

Skipping Gear-by-Gear Adjustment

• Mistake: Focusing on just a few gears during adjustment.
• Effect: Skipping gears may cause inconsistent shifting performance across the cassette.
• Solution: Shift through every gear during adjustments to ensure smooth and accurate shifting throughout the entire range.

Neglecting to Lube the Chain

• Mistake: Adjusting the derailleur without lubricating the chain.
• Effect: A dry or rusty chain can make shifting sluggish, even with proper derailleur adjustment.
• Solution: Always ensure the chain is clean and well-lubricated before making adjustments.

Shimano rear derailleur adjustment vs. replacement.

When to Adjust the Shimano Rear Derailleur:

1. Poor Shifting Performance: If you experience sluggish, noisy, or inaccurate gear shifts, the derailleur likely just needs adjustment. This includes tuning cable tension, limit screws, or the B-screw to ensure smooth gear transitions.

2. Cable Stretch: Over time, the derailleur cable can stretch, affecting shifting. In this case, a simple adjustment using the barrel adjuster can resolve the issue.

3. Minor Misalignment: If the derailleur hanger is slightly bent, realigning it with an adjustment tool can restore proper function without needing a replacement.

4. Normal Wear: If the derailleur is still functional but has shifted out of alignment due to use or routine maintenance (like chain replacement), a fine adjustment is often all that's needed.

When to Replace the Shimano Rear Derailleur:

1. Physical Damage: If the derailleur is bent, cracked, or damaged (due to a crash, for example), it will need to be replaced. Bent derailleur cages or broken jockey wheels typically require a new derailleur.

2. Excessive Wear: Over time, the derailleur’s components (jockey wheels, springs, pivots) can wear out, causing shifting issues that can’t be solved with adjustments. In this case, replacing the derailleur is the best solution.

3. Hanger Damage: If the derailleur hanger is severely bent or damaged, it may be necessary to replace both the hanger and the derailleur, especially if the damage has compromised shifting accuracy.

4. Incompatibility with New Components: If you upgrade other components of your drivetrain, such as switching to a wider-range cassette, your old derailleur may no longer be compatible. In such cases, replacement is needed to ensure compatibility with the new setup.

5. Worn Springs or Pivots: Over time, the tension springs and pivots in the derailleur can wear out, causing poor shifting performance. If these parts are worn and affecting function, replacement is often more practical than repair.

How to avoid chain rubbing after derailleur adjustment

Fine-Tune Cable Tension

• Symptom: Chain rubs when shifting between gears or while riding.
• Fix: Use the barrel adjuster (located on the derailleur or shifter) to fine-tune the cable tension.
  • If the chain is slow to shift up the cassette (toward larger cogs), turn the barrel adjuster counterclockwise to increase tension.
  • If the chain rubs when shifting to smaller cogs, turn the barrel adjuster clockwise to reduce tension.

Adjust the Limit Screws

• Symptom: Chain rubs on the outer or inner side of the cassette.
• Fix: The limit screws control how far the derailleur can move across the cassette. If improperly set, the chain may rub against the derailleur or overshoot its intended gear.
  • Adjust the high limit screw (marked "H") to prevent rubbing in the smallest cog.
  • Adjust the low limit screw (marked "L") to prevent rubbing in the largest cog.

Check the B-Screw Adjustment

• Symptom: Chain rubs or struggles to shift smoothly in the largest cog.
• Fix: The B-screw adjusts the distance between the upper jockey wheel and the cassette. If the jockey wheel is too close to the cassette, it can cause chain rubbing.
  • Turn the B-screw clockwise to increase the gap or counterclockwise to decrease the gap.

Inspect the Chainline

• Symptom: Chain rubs consistently, especially in certain gears.
• Fix: Ensure the chain is running straight and in alignment with the cassette. If the derailleur cage is misaligned (from a bent hanger or improper adjustment), the chain will rub.
  • Check the derailleur hanger for straightness and adjust or replace it if bent.

Check the Front Derailleur (if applicable)

• Symptom: Chain rubs in the front when cross-chaining (using extreme gear combinations like small chainring + small cog or large chainring + large cog).
• Fix: Adjust the front derailleur’s limit screws to ensure the chain is properly aligned with the front chainrings.
  • Avoid cross-chaining, as it puts strain on the drivetrain and can cause chain rubbing.

Lubricate the Chain

• Symptom: Chain noise or rubbing even after adjustments.
• Fix: A dirty or dry chain can cause rubbing and noise. Clean and lubricate the chain regularly to reduce friction and ensure smooth operation.

Test Under Load

• Symptom: Rubbing only occurs while riding.
• Fix: After making adjustments, test the derailleur while riding under load. Shift through all the gears to ensure there is no rubbing, and make fine adjustments as needed.

Should I adjust the B-tension on my Shimano derailleur

When to Adjust the B-Tension:

1. Slow or Noisy Shifting to Larger Cogs: If shifting to the larger gears (bigger cogs) is slow, hesitant, or noisy, it’s often because the upper jockey wheel is too close to the cassette.

2. Rubbing in Larger Gears: If the chain is rubbing or feels tight when using the largest cogs, the B-tension may need to be increased.

3. New Drivetrain Components: After installing a new cassette or chain, or upgrading to a wider-range cassette, adjusting the B-tension ensures the derailleur can handle the different cog sizes.

How to Adjust the B-Tension on Your Shimano Derailleur:

1. Shift to the Largest Cog: Put the e-bike in the lowest gear (largest cog on the rear cassette).

2. Locate the B-Screw: This is the small screw at the top of the derailleur where it attaches to the hanger.

3. Check the Distance: The gap between the upper jockey wheel and the largest cog should be about 5-6mm. If it’s too close or too far, shifting will be affected.

4. Adjust the B-Screw:

   • Turn the B-screw clockwise to increase the gap (moving the derailleur away from the cassette).
   • Turn the B-screw counterclockwise to decrease the gap (moving the derailleur closer to the cassette).

5. Test Shifting: Shift through all gears, especially into the larger cogs, to ensure smooth and quiet transitions. Fine-tune the B-tension as needed.

Why is my Shimano derailleur skipping gears

Cable Tension Issues

• Cause: The derailleur cable might be too loose or too tight, preventing the derailleur from moving smoothly between gears.
• Fix: Use the barrel adjuster to fine-tune the cable tension:
  • If the chain is skipping to a smaller cog, the cable may be too tight; turn the barrel adjuster clockwise to loosen it.
  • If it’s skipping to a larger cog, the cable may be too loose; turn the adjuster counterclockwise to tighten it.

Worn or Stretched Cables

• Cause: Over time, cables can stretch or wear out, causing sluggish or inaccurate shifting.
• Fix: Inspect the cables for fraying or corrosion. If the cables are worn or stretched, replace them to restore smooth shifting.

Dirty or Worn Chain and Cassette

• Cause: A worn-out chain or cassette can cause poor engagement with the gears, leading to skipping.
• Fix: Check if the chain is stretched or the teeth on the cassette are worn down. Clean and lubricate the drivetrain regularly. If parts are worn, replace the chain and cassette together to avoid further skipping.

Misaligned Derailleur Hanger

• Cause: If the derailleur hanger is bent, the derailleur won’t line up properly with the gears, causing the chain to skip.
• Fix: Use a derailleur hanger alignment tool to check if the hanger is straight. If bent, carefully realign it or replace the hanger.

Improper Limit Screw Adjustment

• Cause: The high or low limit screws may be set incorrectly, preventing the derailleur from fully engaging the gears.
• Fix: Adjust the H-screw (high limit) to prevent the derailleur from overshooting the smallest cog and the L-screw (low limit) to prevent overshooting the largest cog.

B-Screw Misadjustment

• Cause: If the B-screw (B-tension screw) is not set correctly, the upper jockey wheel may be too close or too far from the cassette, causing shifting issues in the larger gears.
• Fix: Adjust the B-screw to maintain the correct distance (about 5-6mm) between the upper jockey wheel and the largest cog.

Worn Jockey Wheels

• Cause: The jockey wheels on the derailleur can wear down over time, causing poor chain tension and skipping.
• Fix: Inspect the jockey wheels for wear and replace them if necessary.

Chainline Issues

• Cause: If the chainline (the alignment of the chain between the front chainrings and the rear cassette) is off, the chain can skip between gears.
• Fix: Ensure the front and rear derailleurs are properly aligned and that the chain is in good condition.

Incorrect Gear Shifting Under Load

• Cause: Shifting gears under heavy load or while pedaling hard can cause the chain to skip.
• Fix: Always shift gears while pedaling smoothly, especially when climbing or accelerating, to avoid putting excessive strain on the drivetrain.

What’s the difference between indexing and derailleur adjustment

Indexing

• Definition: Indexing refers to the precise alignment of the derailleur with each individual gear (cog) on the cassette, so that the chain shifts smoothly between gears when you operate the shifter.
• Purpose: To ensure that each click of the shifter moves the derailleur exactly the right amount to line up with the next cog, resulting in accurate and smooth shifting.
• How to Adjust:
  • Typically involves adjusting the barrel adjuster on the shifter or derailleur to fine-tune the cable tension, ensuring the derailleur lines up correctly with the gears.
  • Proper indexing ensures the chain moves cleanly onto each gear without skipping or hesitation.

Derailleur Adjustment:

• Definition: Derailleur adjustment is a broader term that refers to all adjustments made to the rear or front derailleur to ensure it functions properly. This includes setting the limit screws, adjusting the B-tension screw, and aligning the derailleur to prevent chain rub or skipping.
• Purpose: To ensure that the derailleur moves the chain smoothly across the entire cassette or chainrings and stays within its intended range of movement, without over- or undershooting.
• How to Adjust:
  • Adjusting the high and low limit screws to prevent the derailleur from moving too far inward or outward.
  • Adjusting the B-screw to set the proper distance between the derailleur’s jockey wheel and the cassette.
  • Checking the alignment of the derailleur to ensure it’s functioning correctly.

How to align a Shimano derailleur hanger

Tools Needed:

1. Derailleur Hanger Alignment Tool: A special tool used to check and correct the alignment of the hanger. Popular brands include Park Tool's DAG-2.2.
2. Hex Wrench or Multi-Tool: Typically a 5mm or 6mm hex wrench to remove the derailleur.
3. Bike Stand (optional): To hold the bike upright and make the process easier.

Steps to Align a Shimano Derailleur Hanger:

1. Shift the Chain to the Smallest Cog:

• Shift the chain onto the smallest cog at the rear to keep it out of the way while working on the derailleur hanger.

2. Remove the Rear Derailleur:

• Using a hex wrench, loosen and remove the derailleur from the derailleur hanger, leaving the chain on the cassette.
• Carefully set the derailleur aside to prevent damage to the cable or chain.

3. Install the Alignment Tool:

• Attach the derailleur hanger alignment tool to the derailleur hanger in the same place where the derailleur mounts.
• Make sure the tool is securely fastened and aligned straight.

4. Check the Alignment:

• Rotate the alignment tool to different points around the rear wheel (top, sides, bottom) to check the hanger's alignment relative to the wheel rim.
• The tool should maintain the same distance from the wheel’s rim at all points. If the gap changes, the hanger is bent and needs adjustment.

5. Align the Hanger:

• Gently apply pressure to the alignment tool in the direction needed to straighten the hanger. Be careful not to overbend the hanger.
• Check the alignment after each adjustment by rotating the tool and ensuring the distance to the rim is consistent at all points.

6. Reinstall the Derailleur:

• Once the hanger is aligned, remove the alignment tool and reinstall the derailleur using the hex wrench.
• Make sure the derailleur is tightly fastened to the hanger.

7. Test Shifting:

• Shift through all the gears to ensure the derailleur moves smoothly across the cassette without skipping or noise.
• If shifting is still not perfect, fine-tune the derailleur adjustment (limit screws, B-tension, and indexing) as needed.

Should I upgrade or repair my Shimano derailleur

When to Repair Your Shimano Derailleur:

1. Minor Issues: If the derailleur is only experiencing minor issues like misalignment, cable tension problems, or worn jockey wheels, a repair or adjustment can resolve these issues. Routine maintenance (cable replacement, lubrication, jockey wheel replacement) can extend the life of the derailleur without the need for a full replacement.

2. Cost Efficiency: If the cost of the repair is minimal and the derailleur is still in good condition, repair is often the most cost-effective option. Simple adjustments, limit screw tuning, or hanger alignment can bring back smooth shifting.

3. Compatibility: If your derailleur is compatible with your current drivetrain setup and provides satisfactory performance, repair may be all that’s needed.

When to Upgrade Your Shimano Derailleur:

1. Significant Wear or Damage: If the derailleur is significantly worn, damaged, or bent (e.g., from a crash), and repair would cost nearly as much as a new one, an upgrade is a better long-term solution. Damaged derailleur cages or pulleys might warrant a replacement.

2. Performance Goals: If you’re looking for better shifting performance, smoother gear changes, or improved reliability (especially if you ride in demanding conditions like mountain biking or racing), upgrading to a higher-end Shimano derailleur can offer better performance. Shimano’s higher-tier models (like Deore XT, Ultegra, or XTR) offer more precise shifting and durability.

3. Upgrading Other Components: If you’re upgrading other components of your drivetrain (such as moving to a larger cassette or a more advanced groupset), upgrading the derailleur ensures compatibility and maximizes performance. A new derailleur may be necessary if you’re switching from a 10-speed to an 11-speed or 12-speed system, for example.

4. Technological Advancements: Shimano regularly updates its product lines with new technologies (such as Shadow+ clutch derailleurs for reducing chain slap or electronic shifting options like Di2). Upgrading to a newer model might improve overall ride quality and performance, especially for competitive riders or those who want more advanced features.

5. Weight Reduction: If you’re trying to reduce the weight of your ebike, upgrading to a lighter derailleur can make a difference, particularly if you switch to a higher-tier model.