How to Adjust Rear Derailleur
The rear derailleur is a critical component of a bicycle’s drivetrain, directly influencing shifting smoothness and riding efficiency. If you experience poor gear shifting, chain skipping, or delayed gear changes, it may be time to adjust your rear derailleur. This guide will cover how to adjust rear derailleur step by step, from basic to advanced techniques.
Working Principle of Rear Derailleur Adjustment
The derailleur adjustment depends on multiple mechanisms to ensure the chain moves smoothly and precisely across the cassette gears. The foundation of this process lies in the limit screws, which include the high-limit screw (H) and low-limit screw (L). The high-limit screw prevents the derailleur from shifting the chain off the smallest cog and ensures proper alignment between the guide pulley and the smallest gear. The low-limit screw controls the inward movement, preventing the chain from falling into the spokes while ensuring proper alignment with the largest cog. By adjusting these screws, you can define the precise range for chain movement.
The B-tension screw plays a crucial role in adjusting the distance between the upper guide pulley and the largest cog of the cassette. This spacing is vital; if it’s too small, the chain may bind during shifting, while excessive distance can result in sluggish or rough gear changes. Turning the B-tension screw fine-tunes this gap, helping to achieve smoother and more efficient shifting.
Cable tension is another key factor in derailleur adjustment. Using the barrel adjuster to fine-tune cable tension, ensure each shift lever click accurately corresponds to a cog position on the cassette. Increasing cable tension moves the derailleur toward the larger cogs while decreasing it shifts it toward the smaller cogs. The combination of proper cable tension and limit screw adjustments allows precise indexing, ensuring a smooth, quiet, and efficient drivetrain operation.
These components work together to enable the rear derailleur to guide the chain effectively across the cassette, ensuring system reliability and stability under various riding conditions. If you need further clarification on specific parts, I’m happy to provide more detailed explanations
How to Adjust a Rear Derailleur
Your rear derailleur likely needs adjustment if you notice rough shifting, gear skipping, or unusual noises. Follow these detailed steps to adjust the limit screws, B-tension screws, and indexing for precise gear alignment.
Tools You’ll Need:
- 2mm and 4mm hex wrenches
- Or a Phillips screwdriver (depending on your derailleur model)
Before you begin, ensure the bike is stable, and have all necessary tools ready.
1. Adjusting the High and Low Limit Screws
The positions of the high limit (H) and low limit (L) screws are usually on the rear derailleur. They limit the chain’s extreme positions, preventing it from derailing.
High Limit Screw (H): Limits the guide pulley from moving too far outward when on the smallest cog (highest gear).

Low Limit Screw (L): Limits the guide pulley from moving too far inward when on the largest cog (lowest gear).

- Shift the chain onto the largest chainring and smallest cog.
- Use a 4mm hex wrench to loosen the derailleur cable, allowing the derailleur to move freely.
- Adjust the High Limit Screw: Ensure the guide pulley aligns with the smallest cog. Turn the H screw clockwise to move the guide pulley toward the cassette center, or counterclockwise to move it outward.
- Adjust the Low Limit Screw: Push the derailleur to shift the chain onto the largest cog. Ensure the guide pulley aligns with the largest cog. Turn the L screw clockwise to limit excessive inward movement of the guide pulley.
After adjustments, ensure the chain runs smoothly and without unnecessary noise.
2. Indexing Gears
The purpose of the indexing process is to adjust cable tension, ensuring each shift accurately corresponds to a specific gear position.
- Turn the barrel adjuster clockwise until it is fully tightened, then turn it counterclockwise one full turn.
- Pull the gear cable taut and secure it to the derailleur using a 4mm hex wrench. It is recommended to use a torque wrench to tighten the bolt to 6-7 Nm.
- Pedal and test the shifting performance: If shifting is difficult, turn the barrel adjuster counterclockwise to increase tension; If shifting is overly sensitive, turn the barrel adjuster clockwise to reduce tension. Adjust in small increments, turning the adjuster no more than a quarter turn at a time, until the gears shift smoothly.
3. Adjusting the B-Tension Screw
The B-tension screw is used to adjust the distance between the upper guide pulley and the largest cog, ensuring a smooth shifting experience.
- Shift the chain onto the smallest chain at the front and the largest cog at the rear.
- Adjust the B-tension screw: Turn it clockwise to increase the distance between the guide pulley and the cog. Turn it counterclockwise to decrease the distance.
- The ideal distance is 4-6 mm. You can use a hex wrench to measure this gap.
Once the adjustments are finished, test each gear one by one to confirm smooth shifting. If any issues are found, you can fine-tune the tension or limit screws for specific gears. Now your rear derailleur is fully adjusted, and you’re ready to ride with confidence!
How to Adjust and Index a Rear Derailleur?
The following video provides a comprehensive guide on how to adjust a rear derailleur for optimal bicycle shifting performance. It covers the functions of the derailleur, limit screws, indexing, and fine-tuning adjustments to ensure smooth gear changes.
Rear Derailleur Adjustment Tips
The key to adjusting a rear derailleur is precision and patience. Here are some practical tips to help you adjust it more efficiently:
- Ensure the Bike is Clean and in Good Condition
Before starting the adjustment, clean the chain, cassette, and rear derailleur, and check if the derailleur cables are smooth and undamaged. If the cables or housing are worn, it’s recommended to replace them for optimal adjustment results. - Adjust in Order
Start with the high limit screw, followed by the low limit screw, B-tension screw, and finish with indexing adjustments. This ensures no detail is overlooked and helps maintain the best range and tension for the chain. - Use the Barrel Adjuster for Fine-Tuning
If you notice slight shifting issues, use the barrel adjuster for real-time fine-tuning. Rotate it no more than a quarter turn at a time and test shifting after each adjustment until the optimal position is found. - Ensure Proper B-Tension Screw Setting
A too-large gap between the upper guide pulley and the largest cog can cause slow shifting, while a too-small gap can cause the chain to jam. Measuring the ideal 4-6 mm gap ensures smooth shifting. - Test All Gears Repeatedly
After adjustments, test each gear to ensure smooth chain movement. If any gear still has issues, adjust the cable tension or limit screws accordingly. - Check the Shifter Response
Ensure the shifter click corresponds to an accurate gear position. If there’s over-shifting or under-shifting, it’s likely due to cable tension. Fine-tune this with the barrel adjuster.