1. How to Adjust Your Back Derailleur • hornetsecurity.com

When a bicycle’s back derailleur is out of adjustment, shifting gears becomes difficult or impossible. This can be a frustrating problem, especially if you’re trying to tackle a challenging hill. Fortunately, adjusting a back derailleur is a relatively simple process that can be done with a few basic tools. In this article, we’ll walk you through the steps of how to adjust a back derailleur, so you can get your bike shifting smoothly again.

Before you start adjusting your back derailleur, it’s important to identify the problem. There are a few common signs that your derailleur is out of adjustment, such as:
– The chain skipping or jumping gears
– The chain rubbing against the derailleur cage
– The shifter not moving smoothly through the gears
Once you’ve identified the problem, you can start making the necessary adjustments. To begin, you’ll need to loosen the derailleur’s mounting bolt. This bolt is usually located near the top of the derailleur, and it will need to be loosened just enough so that the derailleur can move freely.

Once the derailleur is loose, you can use the barrel adjuster to fine-tune the alignment. The barrel adjuster is a small screw that is located on the derailleur’s cable housing. Turning the barrel adjuster clockwise will tighten the cable, and turning it counterclockwise will loosen the cable. By making small adjustments to the barrel adjuster, you can ensure that the derailleur is properly aligned and that the chain is shifting smoothly through the gears. Once you’ve made the necessary adjustments, tighten the derailleur’s mounting bolt and test the shifting. If the derailleur is still not shifting properly, you may need to repeat the adjustment process.

Understanding the Anatomy of a Back Derailleur

The Derailleur Body

The derailleur body is the central component that houses the main mechanisms of the derailleur. It is typically made of aluminum or a lightweight alloy and is responsible for holding and guiding the pulley wheels that move the chain across the cassette.

The Cage

The cage is the part of the derailleur that holds the pulley wheels and guides the chain. It is made up of two parallel plates that are connected by a parallelogram linkage. The cage moves back and forth to adjust the position of the chain on the cassette.

The Pulley Wheels

The pulley wheels rotate freely on the cage and are responsible for guiding the chain around the cassette. They are typically made of a hard material, such as steel or ceramic, to reduce friction and ensure smooth chain movement.

The Tension Spring

The tension spring is a coiled spring that is attached to the derailleur body and the cage. It provides tension to the cage, keeping it aligned with the cassette and preventing the chain from falling off.

The Limit Screws

The limit screws are two small screws that limit the movement of the cage in each direction. The high-limit screw prevents the cage from moving too far to the right, while the low-limit screw prevents it from moving too far to the left.

The B-Tension Screw

The B-tension screw is used to adjust the distance between the derailleur pulleys and the cassette. This adjustment is critical for optimizing the shifting performance of the derailleur.

Derailleur Component	Description
Derailleur Body	Central component housing the main mechanisms
Cage	Part that holds the pulley wheels and guides the chain
Pulley Wheels	Rotate freely to guide the chain
Tension Spring	Provides tension to the cage
Limit Screws	Limit the movement of the cage
B-Tension Screw	Adjusts the distance between the pulleys and cassette

Identifying the Common Back Derailleur Adjustments

1. Determining the Need for Adjustment

If you notice any unusual chain behavior, such as skipping gears, grinding noises, or difficulty shifting, your back derailleur likely requires adjustment. It’s essential to inspect the derailleur’s alignment and tension to ensure optimal performance.

2. Understanding the Adjustment Screws

The back derailleur consists of two primary adjustment screws:

High Limit Screw: Regulates the derailleur’s movement to the highest gear. When properly adjusted, the derailleur will align the chain with the smallest cog without rubbing against it.
Low Limit Screw: Limits the derailleur’s movement to the lowest gear. Proper adjustment ensures that the chain doesn’t drop off the largest cog while riding.
Steps to Adjust High and Low Limit Screws:

Position the chain on the middle cog.
Turn the high limit screw clockwise to move the derailleur towards the bike frame. This will ensure the chain aligns with the smallest cog.
Turn the low limit screw counterclockwise to move the derailleur away from the bike frame. This will prevent the chain from falling off the largest cog.
Make small adjustments to fine-tune the derailleur’s position.
B-Screw:** Also known as the tension screw, controls the distance between the derailleur’s upper pulley wheel and the largest cog. Proper tension prevents chain slap and helps the derailleur shift smoothly.
Steps to Adjust B-Screw:
Position the chain on the largest cog.
Turn the B-screw clockwise to increase tension.
Turn the B-screw counterclockwise to decrease tension.
Aim for a slight gap between the upper pulley wheel and the cog, approximately 1-2 millimeters.
Indexing Screw:** Used to fine-tune the derailleur’s position in each gear. It adjusts the cable tension to ensure smooth and precise shifting.
Steps to Adjust Indexing Screw:
Shift the chain through all the gears.
If the chain skips or grinds in any gear, turn the indexing screw clockwise to increase tension on the cable.
If the chain doesn’t shift smoothly, turn the indexing screw counterclockwise to reduce tension on the cable.

Gathering the Necessary Tools for Adjustment

Essential Tools:

Before embarking on the adjustment process, it’s crucial to gather the necessary tools to ensure accuracy and precision.

Essential Tool: Allen Wrench

An Allen wrench, also known as a hex key, is essential for adjusting the barrel adjusters. Typically, a 2.5 mm or 3 mm wrench is required for this purpose. Select the correct size based on the diameter of the barrel adjuster bolts on your derailleur.

Essential Tool: Screwdriver (Phillips or Flat Head)

A screwdriver is required to adjust the high and low limit screws on the derailleur. Depending on the design of your derailleur, you may need either a Phillips head or a flat head screwdriver. Consult the manufacturer’s instructions for the specific type required.

Helpful Tools:

While not essential, certain tools can facilitate the adjustment process:

Tool	Purpose
Chain Checker	Assesses chain wear and helps determine if replacement is necessary.
Derailleur Hanger Alignment Tool	Ensures proper alignment of the derailleur hanger, which can affect shifting performance.
Workstand	Provides stability for the bike during the adjustment process, making it easier to shift and observe the drivetrain components.

Setting the High and Low Limit Screws

The high and low limit screws determine the range of motion for the rear derailleur. Adjusting these screws ensures that the derailleur shifts smoothly and prevents the chain from coming off the cassette.

Step 1: Set the Low Limit Screw

Shift the rear derailleur to the smallest cog (on the far right).
Locate the low limit screw, which is typically found on the derailleur body or near the cable clamp.
Turn the screw clockwise until the derailleur cage is barely touching the smallest cog.

Step 2: Set the High Limit Screw

Shift the rear derailleur to the largest cog (on the far left).
Locate the high limit screw, which is typically found on the derailleur body or near the cable clamp.
Turn the screw clockwise until the derailleur cage is barely touching the largest cog without causing any tension on the chain.

Step 3: Check the Chain Wrap

Once the limit screws are set, check the chain wrap by shifting the derailleur through all the gears. The chain should wrap smoothly around each cog, with no skipping or hesitation. If there is any irregularity, adjust the limit screws accordingly.

Step 4: Fine-Tune the Shifts

If the shifting is still not perfect, fine-tune the adjustments by turning the barrel adjuster on the derailleur cable. Turning the barrel adjuster clockwise increases the cable tension, which will shift the derailleur towards the larger cogs. Turning it counterclockwise decreases the cable tension, which will shift the derailleur towards the smaller cogs.

Make small adjustments to the barrel adjuster and shift the derailleur back and forth until the shifting is precise and smooth.

Adjusting Cable Tension

Cable tension is crucial for precise shifting. To adjust it, follow these steps:

Shift the derailleur to the smallest cog.
Locate the barrel adjuster on the cable housing next to the derailleur.
Turn the barrel adjuster clockwise to increase tension or counterclockwise to decrease it.
Shift through all gears to check if the tension is adequate. The chain should move smoothly with minimal hesitation.
Fine-tune the tension by turning the barrel adjuster in small increments until the shifting is precise and effortless.

Indexing

Indexing aligns the derailleur’s position with each cog on the cassette for precise shifting. Here’s how to do it:

Shift to the smallest cog and the largest chainring.
Locate the high-limit screw on the rear derailleur body. It is typically labeled with an “H” or “L” (low).
Turn the high-limit screw clockwise until the chain rubs lightly against the largest cog.
Shift to the largest cog and the smallest chainring.
Adjust the low-limit screw on the derailleur body, labeled with an “L” or “H” (high), to prevent the chain from falling off the cassette.

Troubleshooting Shifting Issues

If you encounter shifting problems after adjusting the derailleur, refer to the following table for troubleshooting:

Issue	Possible Cause
Chain rubbing against derailleur	Insufficient cable tension
Chain slipping on cogs	Excessive cable tension
Difficulty shifting into certain gears	Improper indexing
Chain hanging off the cassette	Low-limit screw not adjusted properly
Derailleur not moving smoothly	Dirty or worn cables

Troubleshooting Back Derailleur Issues

1. Check Cable Tension

Examine the tension of the cable; it should have a slight slack when the bike is in the smallest cog. If the cable is too tight, it can cause hard shifting or even prevent gear changes. Conversely, if it’s too loose, the derailleur may not move correctly, resulting in chain drops or skipping gears.

2. Adjust High and Low Limit Screws

These screws control the derailleur’s range of movement. The high limit screw determines the maximum gear, while the low limit screw sets the minimum gear. If these screws are not adjusted properly, the derailleur may not shift into the desired gears or may overshift.

3. Check Hanger Alignment

The derailleur hanger is a critical component that holds the derailleur in place. A misaligned hanger can cause the derailleur to function poorly. To check the alignment, use a derailleur alignment tool or take the bike to a qualified mechanic.

4. Lubricate All Moving Parts

Proper lubrication keeps the derailleur and its components operating smoothly. Apply a bike-specific lubricant to the pulley wheels, pivot points, and cable housings. This will reduce friction and prevent premature wear.

5. Clean the Derailleur and Chain

Dirt, grime, and rust can accumulate on the derailleur and chain, affecting shifting performance. Regularly clean these components with a degreaser and a brush. After cleaning, apply a small amount of lubricant to the chain.

6. Advanced Troubleshooting: B-Screw Adjustment

The B-screw, also known as the “chain gap screw,” controls the distance between the upper jockey wheel and the smallest cog. This adjustment is crucial for precise shifting and preventing chain rub. To adjust the B-screw, follow these steps:

Shift the bike into the smallest cog.
Measure the gap between the upper jockey wheel and the cog using a chain checker tool.
If the gap is less than 5mm, turn the B-screw clockwise to increase the gap.
If the gap is more than 5mm, turn the B-screw counterclockwise to decrease the gap.
Re-check the gap and make fine-tuned adjustments until it measures between 4-6mm.

B-screw Position	Effect on Shifting
Clockwise	Increases gap, harder shifting into smaller cogs
Counterclockwise	Decreases gap, smoother shifting into smaller cogs

Fine-tuning the Derailleur’s Performance

7. Indexing the Derailleur

Indexing aligns the derailleur’s pulleys with the individual chainrings and cassette cogs. Proper indexing ensures smooth, precise gear changes without chain drops or excessive noise.

Detailed Indexing Procedure:

Shift the chain to the largest chainring and smallest cassette cog.
Adjust the “H” screw so that the derailleur cage is parallel to the largest cog.
Shift the chain to the smallest chainring and largest cassette cog.
Adjust the “L” screw so that the derailleur cage is parallel to the smallest cog.
Shift through the gears to check for any alignment issues.
Make fine adjustments to the “H” and “L” screws as needed.
Test ride the bike to ensure the derailleur is functioning smoothly under load.

Adjusting the Cable Tension

The cable tension adjustment is crucial for accurate shifting. Follow these steps to get it right:

1. Shift to the Highest Gear

Position the bike on a repair stand or flip it upside down. Shift the rear derailleur to the smallest cog (highest gear).

2. Loosen the Barrel Adjuster Counterclockwise

Locate the barrel adjuster on the rear derailleur. Rotate it counterclockwise to loosen the cable tension.

3. Pull the Cable Tight

Grasp the cable housing just above the rear derailleur. Pull it toward the derailleur to remove any slack.

4. Tighten the Barrel Adjuster Clockwise

Rotate the barrel adjuster clockwise until the cable housing becomes taut. Ensure slight resistance when pulling the cable.

5. Shift and Check Alignment

Shift to the second smallest cog (one gear down). The derailleur should move smoothly and align perfectly with the cog.

6. Adjust as Needed

If the alignment is off, repeat steps 3 and 4 to fine-tune the tension. Aim for smooth shifting and precise cog engagement.

7. Tighten the Cable Housing

Hold the cable housing in place as you rotate the barrel adjuster, then tighten the cable housing bolt to secure it.

8. Shifting Troubleshooting Table

Problem	Adjustment
Derailleur shifts too far	Loosen the barrel adjuster
Derailleur shifts too slowly or not enough	Tighten the barrel adjuster
Derailleur makes buzzing or grinding noises	Check for a bent derailleur hanger or misaligned limit screws

Make Fine Adjustments on the Barrel Adjuster

Once you’ve positioned the derailleur hanger, you can fine-tune the shifting by adjusting the barrel adjuster on the derailleur cable. If the chain is consistently overshifting to the smaller cogs (towards the wheel), turn the barrel adjuster counterclockwise a quarter turn at a time until the shifting improves. If the chain is overshifting to the larger cogs (away from the wheel), turn the barrel adjuster clockwise a quarter turn at a time. Retest the shifting after each adjustment, and continue until the shifting is precise.

Set the B-Tension Screw

The B-tension screw adjusts the distance between the upper pulley wheel and the largest cog on the cassette. It should be set so that the pulley wheel is about 4-6mm above the cog when the derailleur is in the largest cog position. To adjust the B-tension screw, use a 2mm hex wrench to turn it clockwise to increase the distance or counterclockwise to decrease the distance. Retest the shifting after each adjustment, and continue until the chain runs smoothly on all the cogs.

Additional Tips for Optimal Back Derailleur Function

Lubricate the Derailleur

A well-lubricated derailleur will shift more smoothly and last longer. Apply a drop of chain lube to the pivot points and pulleys regularly, especially after riding in wet or muddy conditions.

Clean the Derailleur

Dirt and grime can build up on the derailleur over time, which can affect its performance. Use a soft brush or cloth to clean the derailleur regularly, paying attention to the pulleys and pivot points.

Inspect the Chain

A worn or damaged chain can affect the performance of the derailleur. Inspect the chain regularly for signs of wear, such as stretched links or broken pins. Replace the chain if it shows signs of excessive wear.

Calibrate the Shifters

If the shifters are not properly calibrated, they can cause the derailleur to shift improperly. Refer to the manufacturer’s instructions for specific calibration procedures for your shifters.

Adjust the Limit Screws

The limit screws prevent the derailleur from overshifting into the spokes or off the cassette. The high limit screw controls the movement of the derailleur to the largest cog, while the low limit screw controls the movement to the smallest cog. Adjust the limit screws as needed to prevent the chain from falling off the cassette or contacting the spokes.

Use the Correct Cable Tension

Proper cable tension is essential for smooth shifting. If the cable is too tight, the derailleur will shift sluggishly and may cause the chain to skip. If the cable is too loose, the derailleur will not shift properly and may allow the chain to fall off the cassette.

Check for Bent or Damaged Components

A bent or damaged derailleur hanger, derailleur, or shifter can affect shifting performance. Inspect these components regularly for any signs of damage. If you find any bent or damaged components, replace them as soon as possible.

Consider a Professional Tune-Up

If you are having trouble adjusting your back derailleur or if you are not confident in your mechanical abilities, it is best to take your bike to a professional bike mechanic for a tune-up. A professional mechanic can diagnose any problems with your derailleur and make the necessary adjustments to ensure that it is functioning properly.

Lower Limit Screw

Turn the screw clockwise to adjust the lower limit, preventing the derailleur from going too far behind the smallest cog. Make sure the chain doesn’t rub on the inner edge of the pulley cage.

Upper Limit Screw

Turn the screw counterclockwise to adjust the upper limit, ensuring the derailleur won’t go too far in front of the largest cog. Confirm that the chain doesn’t rub on the outer edge of the pulley cage.

Barrel Adjuster

Use the barrel adjuster on the derailleur cable to fine-tune the shifting between gears. Turn the barrel clockwise to increase cable tension, making shifts snappier. Counterclockwise turns reduce tension, improving smoothness.

B-Screw

Adjust the B-screw on the rear derailleur to set the distance between the jockey pulley and the largest cassette cog. It affects shifting precision and chain stability.

Common Pitfalls to Avoid during Adjustment

1. Overtightening the Limit Screws

Avoid overtightening the limit screws, as it can damage the screws or the derailleur itself. Instead, make small adjustments until the desired limits are reached.

2. Insufficient Cable Tension

Ensure there’s enough tension in the derailleur cable. Loose cables can cause shifting delays and ghost shifting (unintentional gear changes).

3. Incorrect B-Screw Setting

An incorrect B-screw setting can lead to poor shifting and chain rub. Measure the distance between the jockey pulley and the largest cassette cog using a standardized ruler or chain checker tool.

4. Dirty or Rusty Components

Clean and lubricate all derailleur components, including the pulleys, cable, and shifter. Dirt and rust can hinder smooth operation and cause premature wear.

5. Bent or Damaged Components

Inspect the derailleur for any bent or damaged parts, such as the hanger, pulleys, or cable guide. Damaged components should be replaced to ensure optimal performance.

6. Incompatible Components

Ensure that the derailleur, shifter, cassette, and chain are compatible. Mismatched components can lead to shifting problems and premature wear.

7. Insufficient Indexing

Properly index the derailleur to ensure smooth and precise shifting between gears. This involves adjusting the barrel adjuster to align the chain with each cog.

8. Ignoring Cable Housing

Pay attention to the length and condition of the derailleur cable housing. Replace worn or damaged housing to eliminate friction and improve shifting.

9. Over-lubrication

Avoid over-lubricating the derailleur and cable. Excess lubrication can attract dirt and dust, compromising performance.

10. Neglecting Test Rides

Always perform test rides after making adjustments to ensure proper shifting and functionality. Make necessary tweaks based on the results of your ride, ensuring the bike is running smoothly.

How To Adjust Back Derailleur

Adjusting a back derailleur is a necessary task for any cyclist who wants to keep their bike in good working order. By following the simple steps outlined below, you can ensure that your derailleur is properly adjusted, giving you the best possible shifting performance.

Step 1: Shift the derailleur to the smallest cog. This will give you the most slack in the cable, making it easier to adjust.

Step 2: Loosen the barrel adjuster on the derailleur. This is located at the end of the cable housing, near the derailleur.

Step 3: Slowly tighten the barrel adjuster until the derailleur is aligned with the smallest cog. You should feel a slight resistance as you tighten the adjuster.

Step 4: Shift the derailleur to the largest cog. This will take up the slack in the cable.

Step 5: Loosen the barrel adjuster until the derailleur is aligned with the largest cog. Again, you should feel a slight resistance as you loosen the adjuster.

Step 6: Shift the derailleur back and forth through all of the gears. Make sure that the derailleur is shifting smoothly and that there is no chain noise.

If the derailleur is not shifting smoothly, you may need to make further adjustments. You can do this by fine-tuning the barrel adjuster or by adjusting the cable tension.