For cyclists, a well-adjusted back derailleur is paramount for a smooth and efficient ride. However, even the most experienced riders may encounter situations where fine-tuning is necessary to optimize performance. Whether you’re experiencing gear slipping, chain noise, or sluggish shifting, making adjustments to your back derailleur can resolve these issues and enhance your cycling experience. In this comprehensive guide, we will delve into the intricacies of back derailleur adjustment, providing step-by-step instructions and valuable tips to ensure your bike is performing at its best.
The back derailleur, often referred to as the rear derailleur, is a crucial component of a bicycle’s drivetrain. Its primary function is to smoothly shift the chain across the cassette, allowing you to effortlessly change gears for varying terrain or riding conditions. When the derailleur is properly adjusted, gear changes occur seamlessly, without hesitation or excessive noise. However, improper adjustment can lead to a myriad of problems, from poor shifting performance to premature wear on your drivetrain components.
Before embarking on the adjustment process, it is essential to understand the basic components of a back derailleur. The derailleur body houses the pulleys that guide the chain, while the cage moves the pulleys to change gears. The cable tension is controlled by a barrel adjuster, typically located on the derailleur or shifter. Additionally, the derailleur features limit screws that set the maximum and minimum travel of the derailleur, ensuring the chain does not fall off the cassette or rub against the spokes. Grasping these concepts will enable you to make informed adjustments and restore your back derailleur to optimal functionality.
Determining the Problem
Identifying Misalignment
The first step in adjusting a back derailleur is accurately identifying misalignment. Misalignment can manifest in several ways:
- Difficulty shifting: If the chain struggles to shift onto or between gears, misalignment could be the culprit.
- Noisy shifting: Excessive noise during shifting often indicates misalignment, as the chain rubs against adjacent cogs.
- Chain dropping: A misaligned derailleur can cause the chain to slip off the cogs, leading to dropped chains.
- Chain sluggishness: In some cases, misalignment can impede the chain’s movement, resulting in sluggish shifting.
Common Causes of Misalignment
Once you’ve identified misalignment, it’s essential to determine the underlying cause to prevent recurrence. Common causes include:
| Cause | Possible Fixes |
|---|---|
| Bent derailleur hanger | Straighten or replace the hanger |
| Loose derailleur bolts | Tighten the bolts to the specified torque |
| Damaged derailleur cable | Replace the cable and housing |
| Worn derailleur components | Replace worn pulleys, guide wheels, or other components |
Gathering Necessary Tools
Before embarking on the task of adjusting your back derailleur, it is essential to gather the necessary tools to ensure a smooth and efficient process. These tools will enable you to perform the adjustments with precision and accuracy.
Chainwhip
A chainwhip is a specialized tool specifically designed for gripping and holding bicycle chains. It features a long, thin handle and a hook-shaped end that engages with the chain links, providing a secure hold. This tool is indispensable for preventing the chain from spinning while adjusting the derailleur.
5mm Allen Key
A 5mm Allen key, also known as a hex key, is a small, L-shaped wrench used for adjusting bolts and screws. In the context of back derailleur adjustment, it is primarily used to tighten or loosen the cable tension bolt, which controls the amount of tension applied to the derailleur cable.
Phillips Head Screwdriver
A Phillips head screwdriver is characterized by its cross-shaped tip, designed to engage with screws featuring a corresponding cross-shaped recess. This tool is used to adjust the derailleur’s B-tension screw, which affects the distance between the derailleur’s upper jockey wheel and the largest cog on the cassette.
Cable Cutter
A cable cutter is a specialized tool used for cutting bicycle cables. It features hardened cutting blades that cleanly and precisely shear through the cable housing and inner wire, ensuring a clean and professional-looking cut.
Additional Tools (Optional)
In addition to the essential tools listed above, the following additional items may prove useful for back derailleur adjustments:
| Tool | Purpose |
|---|---|
| Torque Wrench | Provides precise control over the tightening torque of bolts and screws, ensuring proper tension without overtightening |
| Derailleur Hanger Alignment Tool | Helps align the derailleur hanger, which is the component that connects the derailleur to the frame, ensuring proper alignment and shifting performance |
Adjusting the Barrel Adjusters
The barrel adjuster is a small, cylindrical screw located on the rear derailleur near the derailleur cable. It is used to fine-tune the derailleur’s adjustment and ensure smooth shifting.
To adjust the barrel adjuster:
- Shift the rear derailleur into the highest gear (the smallest cog on the cassette).
- Tighten the barrel adjuster screw clockwise until you hear a slight click.
- Shift the rear derailleur into the lowest gear (the largest cog on the cassette) and check if the chain is running smoothly over all of the gears. If the chain is rubbing on the cassette or not shifting smoothly, continue to the next step.
- If the chain is rubbing on the cassette, loosen the barrel adjuster screw counterclockwise by 1/4 turn. If the chain is not shifting smoothly, tighten the barrel adjuster screw clockwise by 1/4 turn.
- Repeat steps 2-4 until the rear derailleur is shifting smoothly in all gears.
Troubleshooting Troubleshooting Barrel Adjuster Issues
| Issue | Solution |
|---|---|
| The chain is rubbing on the cassette | Loosen the barrel adjuster screw counterclockwise by 1/4 turn |
| The chain is not shifting smoothly | Tighten the barrel adjuster screw clockwise by 1/4 turn |
| The rear derailleur is not shifting into all gears | Check the derailleur cable for damage or slack. If the cable is damaged or slack, replace it or adjust the cable tension accordingly. |
Verifying Chain Tension
To ensure your derailleur is functioning optimally, it’s crucial to verify the chain tension. A properly tensioned chain will provide smooth shifting, avoid premature wear, and prevent slippage.
1. Visual Inspection
Begin by visually inspecting the chain. If it appears loose or excessively slack, it may need tightening. Conversely, if it is so tight that it restricts movement in the derailleur, it will require loosening.
2. Lift Test
With the bike on a flat surface, grab the chain near the rear derailleur and lift it. The chain should lift approximately 1/2-1 inch (1-2.5 cm) from the largest cog. If it lifts more or less than this, adjustments are required.
3. Measuring SAG
Alternatively, you can measure chain sag to determine tension. Shift to the middle gear cassette and position the chain under the second-largest cog. Pull the chain gently to create a slight slack, then place a ruler vertically alongside the chain. The distance from the center of the lower chain roller to the ruler should be around 1/8-1/4 inch (3-6 mm).
| Chain Tension | Visual Inspection | Lift Test | SAG Measurement |
|---|---|---|---|
|
Tight |
Chain restricts movement in derailleur |
Chain lifts less than 1/2 inch (1 cm) |
Less than 1/8 inch (3 mm) |
|
Loose |
Chain appears slack |
Chain lifts more than 1 inch (2.5 cm) |
More than 1/4 inch (6 mm) |
|
Optimal |
Chain appears slightly tensioned |
Chain lifts approximately 1/2-1 inch (1-2.5 cm) |
1/8-1/4 inch (3-6 mm) |
Setting the B-Screw
The B-screw, located on the rear derailleur, adjusts the distance between the top guide pulley and the largest rear cog. A properly adjusted B-screw ensures that the chain properly engages with the cassette and reduces the risk of chain derailment. Follow these steps to adjust the B-screw:
1. Shift to the Largest Rear Cog
Shift the rear derailleur to the largest rear cog and slowly pedal the bike.
2. Observe the Chain Alignment
Check the alignment of the chain as it passes through the top guide pulley. It should be centered between the inner and outer guide plates.
3. Insert the B-Screw Key
Insert the appropriate hex key (mm) into the B-screw. Typically, the B-screw requires a 2-3 mm hex key.
4. Adjust the B-Screw
Turn the B-screw in small increments (1/4 turn). Turning the B-screw clockwise will move the upper guide pulley away from the cassette; turning it counterclockwise will move the pulley closer to the cassette.
5. Fine-Tune the B-Screw
Continue adjusting the B-screw in small increments while observing the chain alignment. You want to achieve precise alignment where the chain runs smoothly and without any rubbing or rattling. This may require several iterations of adjusting, shifting, and fine-tuning. A properly adjusted B-screw will ensure optimal shifting performance and prevent premature wear on your drivetrain.
Fine-Tuning the Indexing
1. Locate the barrel adjuster on the derailleur. It is typically a small, round knob located on the top or bottom of the derailleur body.
2. Turn the barrel adjuster clockwise to increase the cable tension, which will move the derailleur inward. Turn the barrel adjuster counterclockwise to decrease the cable tension, which will move the derailleur outward.
3. Pedal the bike while adjusting the barrel adjuster, and shift through the gears.
4. Observe the chain’s movement as it shifts through the gears. If the chain is rubbing against the inside of the cassette, turn the barrel adjuster counterclockwise to reduce the cable tension. If the chain is rubbing against the outside of the cassette, turn the barrel adjuster clockwise to increase the cable tension.
5. Continue making small adjustments to the barrel adjuster until the chain is shifting smoothly and quietly through all the gears.
6. Check the B-tension. The B-tension is the distance between the top jockey wheel and the largest cassette cog. It should be set so that the jockey wheel is parallel to the cassette cog when the chain is in the largest cog. To adjust the B-tension, use a 5mm hex key to turn the screw located on the back of the derailleur. Turn the screw clockwise to increase the B-tension, and counterclockwise to decrease the B-tension.
| Setting | B-tension | Jockey Wheel Alignment |
|---|---|---|
| Too low | Chain rubs against cassette | Jockey wheel is angled towards cassette |
| Too high | Chain skips on cassette | Jockey wheel is angled away from cassette |
| Correct | Chain shifts smoothly | Jockey wheel is parallel to cassette |
Troubleshooting Common Issues
1. The chain drops off the derailleur
This can be caused by a number of factors, including:
- The derailleur is not properly adjusted
- The chain is too long or too short
- The derailleur is damaged
2. The shifting is sluggish or erratic
This can be caused by a number of factors, including:
- The derailleur cables are too tight or too loose
- The derailleur is dirty or needs lubrication
- The derailleur is damaged
3. The chain makes a grinding noise when shifting
This can be caused by a number of factors, including:
- The derailleur is not properly adjusted
- The chain is too worn
- The derailleur is damaged
4. The rear derailleur is not shifting into the smallest cog
This can be caused by a number of factors, including:
- The derailleur cable is too tight
- The derailleur is damaged
- The derailleur hanger is bent
5. The rear derailleur is not shifting into the largest cog
This can be caused by a number of factors, including:
- The derailleur cable is too loose
- The derailleur is damaged
- The derailleur hanger is bent
6. The derailleur is rubbing against the chain
This can be caused by a number of factors, including:
- The derailleur is not properly adjusted
- The derailleur is bent
- The cassette is worn
7. The derailleur limit screws are out of adjustment
The derailleur limit screws control the maximum and minimum travel of the derailleur. If the limit screws are out of adjustment, the derailleur may not be able to shift into all of the gears. To adjust the limit screws, follow these steps:
- Shift the derailleur into the highest gear.
- Turn the upper limit screw clockwise until the derailleur stops moving.
- Turn the upper limit screw counterclockwise until the derailleur just starts to move.
- Shift the derailleur into the lowest gear.
- Turn the lower limit screw clockwise until the derailleur stops moving.
- Turn the lower limit screw counterclockwise until the derailleur just starts to move.
Causes Possible Solutions Cable tension is too high or too low Adjust the derailleur cable Chain is too long or too short Replace the chain Derailleur is bent or damaged Replace the derailleur Preventing Future Adjustments
8. Keep Your Chain Clean and Lubricated
A dirty or dry chain can increase friction and cause the derailleur to shift poorly. Regularly clean and lubricate your chain using a bike chain cleaning kit and a chain lube specifically designed for bike chains. This will help reduce wear and tear on the chain and derailleur, and prevent the need for frequent adjustments.
Here are some additional tips to help prevent future derailleur adjustments:
- Avoid shifting under heavy load. When climbing hills or accelerating, shift to an easier gear before applying significant force to the pedals.
- Keep your bike in good repair. Ensure that the cables and housing are free of rust and debris, and that the jockey wheels and pulleys are clean and functioning properly.
- Have your bike serviced regularly by a qualified mechanic. A professional tune-up can identify and fix minor issues before they become major problems.
- Store your bike in a dry, clean place. Exposure to moisture and dirt can cause the derailleur to corrode or become contaminated.
Adjustment Frequency Chain cleaning and lubrication Every 1-2 rides Derailleur fine-tuning As needed (after cleaning, after a fall, etc.) Safety Precautions
Before beginning any adjustments to your back derailleur, it is important to take the following safety precautions:
- Wear appropriate safety gear. This includes gloves, eye protection, and appropriate clothing.
- Secure your bicycle. Place your bicycle in a stable position with the chain on the smallest cog in the rear and the smallest chainring in the front.
- Use the correct tools. You will need a set of Allen keys or a derailleur adjustment tool.
- Be patient. Derailleur adjustments can be time-consuming and require patience.
- Follow the instructions carefully. If you are unsure about any step, consult a professional.
- Do not overtighten the bolts. Overtightening can damage the derailleur or the frame of your bicycle.
- Test ride your bicycle after making adjustments. This will help you ensure that the derailleur is working properly.
- Repeat the adjustment process as needed. It may take several adjustments to get the derailleur perfectly tuned.
9. Adjusting the B-Screw
The B-screw adjusts the distance between the upper pulley wheel of the rear derailleur and the largest cog on the cassette. It is important to set the B-screw correctly to prevent the chain from rubbing against the cassette when in the largest gear.
To adjust the B-screw, turn the screw clockwise to move the pulley wheel away from the cassette and counterclockwise to move it closer to the cassette. The correct B-screw setting will vary depending on the specific derailleur and cassette you are using.
As a general guideline, the distance between the upper pulley wheel and the largest cog should be 4-6 mm. You can use a ruler or a Park Tool Chain Checker to measure this distance.
Once you have adjusted the B-screw, test ride your bicycle to make sure that the derailleur is shifting smoothly and without any chain rub.
Additional Tips and Tricks
1. Use a Derailleur Alignment Tool:
Invest in a dedicated derailleur alignment tool to ensure precise adjustments. It simplifies the process and enhances the accuracy of your setup.2. Check the Cable Tension:
Verify that the derailleur cable has the correct tension. If it’s too tight, it can cause shifting issues. If it’s too loose, the chain may drop off the gears.3. Lubricate Regularly:
Lubricate all the moving parts of the derailleur, including the pulleys, pivots, and cable housing. Regular lubrication reduces friction and improves shifting performance.4. Clean the Derailleur:
Keep the derailleur clean by wiping it down with a damp cloth or using a degreaser. Dirt and grime can interfere with smooth operation.5. Check for Bent Parts:
Inspect the derailleur for any bent parts, such as the derailleur hanger or cage plates. Even minor bends can affect shifting performance.6. Use a Chain Wear Gauge:
A chain wear gauge can help you determine if your chain is worn or stretched. A worn chain can cause shifting problems, so it’s important to replace it when necessary.7. Adjust the B-Screw:
The B-screw limits the maximum travel of the top derailleur pulley. Adjusting it can fine-tune the shifting performance in the highest gears.8. Use a Cable Catcher:
Installing a cable catcher can prevent the derailleur cable from falling off the pulley wheel if it accidentally comes loose.9. Consider a Clutch Rear Derailleur:
Clutch rear derailleurs reduce chain bounce and prevent the chain from dropping off the gears, especially during rough terrain riding.10. Index the Derailleur:
Indexing involves aligning the derailleur with the gears and ensuring that each gear shift is smooth and precise. This can be a time-consuming process, but it’s essential for optimal shifting performance. Here’s a step-by-step guide to indexing a derailleur:Step Description 1 Shift to the smallest cog. 2 Adjust the L-screw using the appropriate tool to align the derailleur guide pulley with the cog. 3 Shift to the largest cog. 4 Adjust the H-screw to align the guide pulley with the cog. 5 Check the shifting performance in all gears. Make fine adjustments to the L- and H-screws as needed. How to Adjust a Back Derailleur
A properly adjusted back derailleur is essential for smooth and efficient shifting. If your derailleur is not adjusted correctly, you may experience problems such as dropped chains, missed shifts, or difficulty shifting under load. Here is a step-by-step guide on how to adjust a back derailleur:
- Check the cable tension. The cable tension should be tight enough to prevent the chain from slipping off the gears, but not so tight that it makes it difficult to shift. To check the cable tension, hold the derailleur in the middle of its travel and try to move the chain from one gear to the next. If the chain moves easily, the cable tension is correct.
- Adjust the low limit screw. The low limit screw prevents the derailleur from overshifting into the spokes. To adjust the low limit screw, turn it clockwise until the derailleur stops moving. Then, turn it counterclockwise until the derailleur can just clear the smallest gear.
- Adjust the high limit screw. The high limit screw prevents the derailleur from overshifting into the frame. To adjust the high limit screw, turn it clockwise until the derailleur stops moving. Then, turn it counterclockwise until the derailleur can just clear the largest gear.
- Check the indexing. The indexing is the process of adjusting the derailleur so that it shifts smoothly and accurately. To check the indexing, shift the chain from one gear to the next and make sure that it lands squarely on the gear. If the chain does not land squarely on the gear, the derailleur needs to be indexed. To index the derailleur, turn the barrel adjuster clockwise or counterclockwise until the chain lands squarely on the gear.
People Also Ask About How to Adjust a Back Derailleur
How often should I adjust my back derailleur?
You should adjust your back derailleur whenever you experience shifting problems, such as dropped chains, missed shifts, or difficulty shifting under load.
Can I adjust my back derailleur on my own?
Yes, you can adjust your back derailleur on your own with a few simple tools. However, if you are not comfortable working on your bike, it is best to take it to a bike shop.
How much does it cost to have my back derailleur adjusted?
The cost of having your back derailleur adjusted at a bike shop will vary depending on the shop and the complexity of the adjustment. However, you can expect to pay between $15 and $30 for a basic adjustment.
