How to Adjust a Rear Derailleur: Fix Bike Gears That Won’t Shift

When one click of the shifter produces a delayed shift, a noisy chain, or no movement at all, the rear derailleur may need attention. But poor shifting is not always caused by the derailleur itself. Cable friction, a bent derailleur hanger, incorrect limit settings, a poorly seated rear wheel, or worn chain and cassette parts can produce similar symptoms.

This guide explains how to adjust rear derailleur settings on a mechanical drivetrain, how to fine-tune indexing, and how to diagnose common shifting faults before turning adjustment screws. It is written for riders who want a practical rear derailleur adjustment process—not a collection of random screw-turning tips.

The steps below focus on a mechanical rear derailleur. Electronic shifting systems use different procedures. If you are learning how to adjust bike gears or how to adjust bicycle gears for the first time, identify your exact derailleur and shifter before following model-specific settings.

1. How a Rear Derailleur Works

A rear derailleur moves the chain across the cassette at the back wheel. On a cable-operated system, each shifter click pulls or releases a measured amount of inner cable. The derailleur moves in response, and its upper guide pulley should line up with the selected sprocket.

Correct indexing means one click produces one clean shift. The main adjustment points are:

• Barrel adjuster: fine-tunes cable tension so the guide pulley aligns with each sprocket.
• H-limit screw: restricts outward travel at the smallest sprocket.
• L-limit screw: restricts inward travel at the largest sprocket and helps prevent the chain entering the spokes.
• B-tension screw: controls the gap between the guide pulley and the cassette.

These controls do different jobs. A barrel adjuster cannot correct a bent hanger, and limit screws should not be used to compensate for worn cables or a poorly indexed drivetrain. Understanding that distinction is the foundation of reliable bike gear adjustment.

2. Diagnose the Problem Before Adjusting

Before attempting a bike derailleur adjustment, identify when the fault occurs. The pattern often points to the cause more accurately than the sound alone.

Symptom	First checks
Slow shift toward larger rear sprockets	Cable tension, cable friction, housing condition and hanger alignment.
Slow shift toward smaller rear sprockets	Cable or housing friction, excess cable tension, or a sticky derailleur pivot.
Chain cannot reach the smallest or largest sprocket	Cable tension and the relevant H or L limit; check the hanger before changing settings.
Chain tries to fall beyond the cassette	Stop riding. Inspect the limit setting and hanger alignment before further shifting.
A jump occurs only under hard pedalling or on one worn sprocket	Check chain wear and cassette teeth. Indexing may not be the cause.
Several gears are noisy or misaligned in different ways	A bent derailleur hanger, damaged cable housing, loose wheel or worn drivetrain parts.

A bent derailleur hanger is especially important. The derailleur can appear to be adjusted correctly in one part of the cassette while shifting poorly elsewhere. Repeatedly turning the barrel adjuster will not straighten the hanger. Park Tool and SRAM both recommend checking hanger alignment and component condition before fine-tuning cable tension.

3. Tools and Safety Checks

For a basic rear-derailleur check, prepare:

• A stable bicycle repair stand, or a safe way to lift the rear wheel.
• The correct hex key or screwdriver for the cable fixing bolt and limit screws.
• A clean rag and good lighting.
• A chain-wear checker if the chain has been used for a long time or the chain jumps under load.
• A torque wrench when the component or frame manufacturer specifies a torque value for a bolt you need to loosen or reinstall.

E-bike safety: switch the bike off before working around the drivetrain. Remove the battery if the model allows it and the manufacturer's instructions recommend doing so. Keep fingers, clothing and tools away from the chain, cassette and spokes. Never use the throttle or pedal-assist system while your hands are near moving drivetrain parts.

4. How to Adjust a Rear Derailleur Step by Step

If you are searching for how to adjust bike derailleur settings or how to adjust gears on a bike, use the following process as a diagnostic sequence. If the bike has recently had a derailleur, cable or hanger replaced, follow the exact installation order in that component's manual.

Step 1: Check the wheel, hanger and cable

1. Make sure the rear wheel is fully seated and secured in the frame.
2. Look from behind the bike to see whether the derailleur cage appears visibly twisted or angled. A damaged or bent hanger needs proper alignment or replacement.
3. Check that the inner shift cable is seated in its fixing groove and that the housing ends are fully inserted into their stops.
4. Look for frayed strands, rust, crushed housing or sharp bends. Replace damaged or heavily contaminated cable parts rather than trying to tune around friction.
5. Check that the chain is correctly routed through both derailleur pulleys.

If the cable is rusty, frayed or binding inside the housing, stop here and replace the affected parts. Cable friction can make shifting slow in both directions and can make a correct adjustment seem inconsistent.

Step 2: Check the H-limit at the smallest sprocket

Shift to the smallest rear sprocket while turning the crank gently. Viewed from behind, the guide pulley should sit in line with the smallest sprocket. The H-limit screw controls the derailleur's outward travel at this end of the cassette.

Do not turn the H screw simply because shifting feels slow. First confirm that the derailleur is actually being stopped by the limit. If the chain tries to move beyond the smallest sprocket, stop pedalling and correct the cause before riding. Make only small adjustments and consult the derailleur manual for the correct screw location and direction.

Step 3: Fine-tune indexing with the rear derailleur barrel adjuster

The rear derailleur barrel adjuster is used for small cable-tension corrections. Start with the chain on a middle sprocket where the chain line is easy to observe. Turn the crank slowly and shift one click at a time.

• If the chain hesitates when moving toward a larger sprocket, the cable may need slightly more tension. On many mechanical systems, turning the adjuster counterclockwise increases tension.
• If the chain hesitates when moving toward a smaller sprocket, the cable may have too much tension. On many systems, turning the adjuster clockwise reduces tension.
• Make a small change—about a quarter turn—then test the same shift again. Repeat only as needed.

These directions are common, not universal. The adjuster's orientation and the component's cable routing matter. Shimano's SIS procedure and SRAM's mechanical adjustment guidance both use the adjuster to fine-tune indexing, but always confirm the instructions for the exact component fitted to your bike.

Step 4: Check the L-limit at the largest sprocket

The L-limit screw controls inward travel toward the largest rear sprocket. It helps prevent the chain and derailleur from moving beyond the cassette and into the spokes.

Shift toward the largest sprocket carefully while turning the crank by hand or with very light pressure. The guide pulley should align with the largest sprocket. If the chain tries to move past the largest sprocket toward the spokes, stop immediately. Do not continue pedalling or ride the bike until the limit and hanger have been checked.

The correct alignment and adjustment method are component-specific. If you cannot identify the L screw or confirm the derailleur's position, have a qualified mechanic set the limit.

Step 5: Check B-tension and guide-pulley clearance

The B-tension screw changes the distance between the upper guide pulley and the cassette. If the pulley is too close, it may contact the sprocket or create noise. If it is too far away, shifting can become less precise.

There is no single B-gap measurement that applies to every rear derailleur. Shimano's dealer manual gives different instructions for different models: some models are adjusted so the guide pulley is as close to the sprocket as possible without touching, while specified RD-TY21B and RD-TZ500 setups use a 10 mm reference. Do not apply that 10 mm figure to an unidentified derailleur.

Step 6: Test every gear

1. Turn the crank gently and shift one click at a time through the cassette.
2. Confirm that each click produces one shift and that the chain runs quietly on each sprocket.
3. Shift back through the cassette and check both directions.
4. Listen for rubbing, hesitation or repeated clicking.
5. Only after the drivetrain shifts correctly on the stand should you perform a cautious low-load test ride.

This is the practical answer to how to fix bike gears when the cause is minor indexing drift. If the problem remains after the checks above, do not keep turning screws at random.

5. Shimano Rear Derailleur Adjustment on a 7-Speed E-Bike

If you are researching Shimano rear derailleur adjustment or how to adjust Shimano rear derailleur settings, start by identifying the model number printed on the derailleur. Shimano has multiple rear-derailleur families and different shifter combinations. A 7-speed label alone does not identify the exact derailleur or its adjustment values.

The EMOKO EC20 product page lists a 7-speed Shimano drivetrain. It does not identify the exact rear-derailleur model in the public specification. If you own an EC20, check the model code on the fitted component before using a model-specific setup chart. You can see the EMOKO EC20 specifications here.

For Shimano rear derailleur adjustment, Shimano's own dealer documentation is the primary reference. Its SIS procedure uses a controlled shift from the smallest sprocket to the next sprocket, then fine-tunes the cable adjustment barrel until the chain shifts cleanly without persistent noise. The same manual also explains that the B-tension setting depends on the derailleur model.

Do not assume the EC20 uses a particular TOURNEY model such as RD-TY300 unless the component label confirms it. Shimano's dealer's manual for REVOSHIFT and TOURNEY shifters and the manual for the exact rear derailleur should take priority over a generic online guide.

6. Common Shifting Problems and What to Check

Bike gears not shifting after one click

If bike gears are not shifting consistently, check whether the cable moves freely and whether the hanger is aligned. A small indexing correction may help, but a seized cable, damaged housing or bent hanger needs repair rather than more barrel-adjuster turns.

Bicycle gears not shifting into the largest sprocket

If bicycle gears are not shifting into the largest sprocket, check cable tension, the L-limit setting and hanger alignment. Do not loosen the L screw without confirming that the chain will not be pushed into the spokes.

Rear derailleur not shifting at all

If the rear derailleur is not shifting, inspect the shifter cable at both ends. The cable may have snapped, slipped from the fixing bolt or become stuck inside the housing. Also check for a loose derailleur mounting bolt or a damaged shifter. If the shifter clicks but the cable does not move, the problem may be at the shifter rather than the derailleur.

How to tune bike gears after a cable replacement

New cable ends and housing can settle after installation, leaving extra slack. Recheck indexing after the first few rides and make small corrections with the barrel adjuster. If you need to how to tune bike gears from a fresh installation, use the component manufacturer's full setup sequence rather than adjusting only by sound.

If you are looking for how to fix gears on a bike, remember to inspect the hanger, cable, cassette and chain as well as the derailleur. One adjustment cannot repair a worn or damaged part.

7. When Chain Skipping Is Not an Indexing Problem

A chain that jumps under strong pedal pressure—especially on one or two frequently used sprockets—may indicate a worn chain or cassette rather than a rear-derailleur indexing fault. A chain-wear checker can help assess chain condition.

Changing cable tension may temporarily alter the noise, but it will not restore worn chain rollers or damaged cassette teeth. If the chain skips under load, inspect wear before continuing to ride. See our existing e-bike chain maintenance and replacement guide for a separate explanation of chain wear and replacement.

8. When to Use a Professional Mechanic

Stop DIY adjustment and ask a qualified bicycle mechanic if:

• The derailleur hanger is visibly bent or the chain has entered the spokes.
• The derailleur, hanger or frame mounting point is cracked or loose.
• The cable is frayed inside the shifter or cannot be removed normally.
• The chain or cassette is badly worn, damaged or repeatedly skips under load.
• You cannot identify the H, L or B-tension adjustment points on the installed model.
• Shifting remains inconsistent after the wheel, hanger, cable and drivetrain have been checked.

For general inspection intervals and other routine checks, see the EMOKO e-bike maintenance guide.

9. Frequently Asked Questions

How often should I adjust a rear derailleur?

There is no fixed calendar interval. Check shifting whenever it becomes noisy or hesitant, after a cable replacement, after the bike takes an impact, or when the rear wheel has been removed and reinstalled. Routine cleaning and inspection help prevent problems from building up.

Can the barrel adjuster fix every shifting problem?

No. It fine-tunes cable tension for indexing. It cannot straighten a bent hanger, repair a broken cable, restore worn cassette teeth or correct a damaged derailleur.

Can I adjust bike gears without a repair stand?

Yes, for a small indexing check, but the bike must be stable and the rear wheel must be able to turn safely. A repair stand makes it easier to observe the chain and guide pulley. Keep your hands away from the moving drivetrain.

Why does one gear keep making noise?

A single noisy sprocket can indicate indexing that is slightly out, a bent hanger, a damaged sprocket or a worn chain-and-cassette combination. Check the hanger and drivetrain condition before making repeated cable adjustments.

Can I adjust an e-bike derailleur while the motor is on?

No. Switch the e-bike off and keep the motor from engaging while you work. Shift by turning the crank manually and using the shifter normally; never use the throttle or pedal assist during a drivetrain adjustment.

10. Technical References 

• Park Tool: Rear Derailleur Adjustment — limit screws and indexing.
• Park Tool: Rear Derailleur Advanced Troubleshooting — cable friction, hanger and drivetrain diagnosis.
• Shimano: REVOSHIFT / TOURNEY Dealer's Manual — SIS adjustment and model-specific B-tension guidance.
• SRAM: Rear Gear Adjustment — hanger alignment, cable adjustment and drivetrain checks.
• EMOKO EC20 product specifications — 7-speed Shimano drivetrain listing.

Final check: A smooth-shifting drivetrain depends on more than cable tension. Confirm the wheel is secure, the hanger is aligned, the cable moves freely, the limits are safe and the chain and cassette are in good condition. Make small changes, test one gear at a time, and use the manual for the exact component fitted to your bike.