how to adjust back derailleur on mountain bike

How to Adjust the Back Derailleur on a Mountain Bike

Maintaining a mountain bike is crucial for optimal performance and a smooth riding experience. One of the key components that require periodic adjustment is the back derailleur. The back derailleur plays a pivotal role in shifting the chain across the cassette gears, and any misalignment can lead to poor shifting performance and increased wear on the drivetrain. In this article, we’ll walk you through the step-by-step process of adjusting the back derailleur on your mountain bike.

What You’ll Need

Before you start, gather the following tools and materials

- A 5mm Allen wrench (or the appropriate size for your derailleur screws) - A Phillips or flathead screwdriver - Bike lubricant - A clean rag or cloth - A bike stand (optional, but helpful)

Step 1 Assess the Current Alignment

Begin by ensuring that your bike is in a stable position. If you have a bike stand, this is the perfect time to use it. Inspect the derailleur and the gear shifting action. Shift through the gears and listen for any skipping or grinding noises. Check if the chain is staying in place on the intended gear without any issue.

Step 2 Check the Limit Screws

The limit screws control the maximum and minimum movement of the derailleur. There are typically two limit screws (marked ‘H’ for high gear and ‘L’ for low gear) that prevent the chain from shifting off the gears.

- To adjust, start with the 'H' screw. Shift your bike to the highest gear (smallest cog). If the chain is unable to reach the smallest cog, turn the 'H' screw clockwise until the derailleur moves into alignment with the cog. If the chain shifts beyond the cog, turn the screw counterclockwise until it stops correctly.

- Next, shift to the lowest gear (largest cog) and check the 'L' screw. Adjust it similarly to ensure that the derailleur does not push the chain off the largest cog.

Step 3 Adjust the Cable Tension

Once the limit screws are set, you may need to adjust the cable tension

. If your derailleur is not shifting smoothly, inadequate or excessive cable tension might be the culprit.

- To adjust, locate the barrel adjuster on the derailleur or where the cable attaches to the shifter. Turn the barrel adjuster counterclockwise to increase tension and clockwise to decrease it.

how to adjust back derailleur on mountain bike

- Test the shifting through the gears. If it feels sluggish or misses gears, make small adjustments and retest until satisfied.

Step 4 Align the Derailleur Body

The derailleur arm should be parallel to the cogs in the chosen gear. If it appears tilted, you may need to slightly adjust the position of the derailleur.

- Loosen the mounting bolt with your 5mm wrench. Position the derailleur so that it is parallel to the cogs and retighten the bolt.

- Check again to ensure the alignment hasn’t shifted when tightening.

Step 5 Fine-Tune the B-Screw

The B-screw adjusts the distance between the derailleur pulley and the cassette. A proper distance ensures smooth chain movement and prevents the chain from rubbing against the derailleur when on the larger cogs.

- To adjust, look for the B-screw, typically located on the back of the derailleur. Shift to the largest cog and ensure there’s around a 5-6mm gap between the upper pulley and the cog.

- Adjust the B-screw accordingly by turning it clockwise to decrease the gap or counterclockwise to increase it.

Step 6 Test Ride

After making all the necessary adjustments, it’s time for a test ride. Go through all the gears while riding to ensure that shifting is smooth and precise. Listen for any unusual noises and feel for any hesitation in shifting.

Conclusion

Adjusting the back derailleur on your mountain bike is a straightforward process that can significantly enhance your riding experience. Regular maintenance not only prolongs the life of your components but also ensures you get the most out of your bike. Whether you’re hitting the trails or cruising through town, correctly adjusted gears will make all the difference in your ride. Don’t hesitate to revisit this process as necessary, and happy cycling!