how to adjust rear derailleur on a mountain bike

How to Adjust the Rear Derailleur on a Mountain Bike

Adjusting the rear derailleur on a mountain bike is an essential skill for any cyclist who wants to ensure their bike shifts smoothly and accurately. Proper adjustment can enhance your riding experience, help prevent premature wear on components, and maintain optimal performance. This guide will walk you through the steps needed to adjust your rear derailleur effectively.

Understanding the Rear Derailleur

The rear derailleur is a mechanism that moves the chain between the various gears located on the cassette attached to the rear wheel of your bike. When the shifter is activated, it pulls or releases the cable connected to the derailleur, allowing it to shift the chain onto the selected gear. Proper alignment and tension of the derailleur are vital for smooth shifting.

Tools You Will Need

Before starting the adjustment process, gather the necessary tools - Phillips screwdriver or flathead screwdriver - Allen wrenches (usually 4mm or 5mm) - Chain checker (optional) - Lubricant (for the chain and derailleur)

Step-by-Step Adjustment Process

1. Inspect the Derailleur and Components

Start by inspecting the rear derailleur, chain, cassette, and shifter for any signs of damage or excessive wear. Ensure that the derailleur hanger is straight; a bent hanger can cause shifting issues. If you find any worn components, consider replacing them before making adjustments.

2. Check the Cable Tension

Cable tension is crucial for accurate shifting. To check the tension - Shift to the largest chainring in the front and the largest sprocket on the cassette. - Pull on the derailleur cable slightly and see if it engages smoothly. - If the derailleur doesn’t shift up or down when adjusting the shifter, you may need to tighten the cable. To do this, locate the barrel adjuster on the derailleur or shifter, and turn it counterclockwise to increase tension.

3. Set the Limit Screws

Limit screws control how far the derailleur can move, which prevents the chain from falling off the gears. There are two limit screws the high limit (for the smallest sprocket) and the low limit (for the largest sprocket).

- High Limit Adjustment - Shift to the smallest rear sprocket. - Look at the derailleur; it should align with the sprocket. If it’s too far away or overlapping, use a screwdriver to adjust the high limit screw (marked with an “H”). Turn it clockwise to move the derailleur inward and counterclockwise to move it outward.

- Low Limit Adjustment - Shift to the largest rear sprocket. - Check the alignment again. Use the low limit screw (marked with an “L”) to make similar adjustments as needed.

4. Fine-Tune the B-Screw

The B-screw adjusts the distance between the derailleur and the cassette. A proper gap ensures that the chain shifts without rubbing on the larger sprockets. With the chain on the largest sprocket, you may need to adjust the B-screw to achieve a distance of 5-6mm between the top of the derailleur's roller and the sprocket. Turn the screw clockwise to lower the derailleur and counterclockwise to raise it.

5. Test the Shifting

Now it’s time to test the shifting - Shift through all the gears while pedaling gently to see how smoothly the chain transitions between the gears. - If you notice any skipping or hesitations, revisit the cable tension and limit screw adjustments.

6. Lubricate the Chain and Derailleur

After adjustments, ensure that your chain and derailleur are properly lubricated to ensure optimal performance. Wipe off any excess lubricant and let it soak in.

Conclusion

Adjusting the rear derailleur on your mountain bike is a straightforward process that can significantly enhance your riding experience. Regular maintenance and adjustments not only improve shifting performance but also extend the lifespan of your components. With practice, you’ll be able to perform these adjustments efficiently, ensuring a smooth and enjoyable ride. Happy cycling!