Step-by-step guide to changing rear derailleur on your mountain bike

How to Replace the Rear Derailleur on a Mountain Bike

Replacing the rear derailleur on a mountain bike might seem daunting, but with the right tools and some basic mechanical knowledge, you can do it yourself. The rear derailleur plays a crucial role in the performance of your bike, managing the shifting between gears and ensuring a smooth ride. If you notice issues like difficulty shifting or unusual noises coming from the rear, it might be time for a replacement. Here’s a step-by-step guide to help you through the process.

Tools You Will Need

Before you start, gather the following tools

1. 5mm Allen wrench 2. Screwdriver (flathead and Phillips) 3. Chain tool (if you need to remove the chain) 4. Torque wrench (optional) 5. Bike stand (optional but recommended for easier access)

Step 1 Remove the Rear Wheel

To begin the replacement, you need to remove the rear wheel. Shift your chain onto the smallest cog (the smallest gear) on the rear cassette. This reduces tension on the derailleur and makes removal easier. Use a 15mm wrench or a quick-release lever to take the wheel off the bike frame.

Step 2 Remove the Chain

If your derailleur is still connected to the chain, you’ll need to remove it. Use a chain tool to break the chain at a link. Alternatively, if your bike has a quick-link chain, you can simply undo that link without any tools.

Step 3 Disconnect the Derailleur

Locate the mounting bolt of the rear derailleur, usually found right above the rear axle. Use the 5mm Allen wrench to unbolt it. After removing the bolt, carefully detach the derailleur from the hanger. It’s essential to keep the screws and parts together in case you need them later.

Step 4 Prepare the New Derailleur

Once the old derailleur is removed, unpack your new rear derailleur and compare it with the old one. Check for compatibility with your bike's cassette and chain type. Many mountain bikes utilize either Shimano or SRAM derailleurs, so ensure that your new part matches your current setup.

Step 5 Install the New Derailleur

Position the new derailleur onto the derailleur hanger and align it with the bolt holes. Insert the bolt and tighten it with the Allen wrench. Be cautious not to over-tighten, as this can damage the hanger. If you have a torque wrench, refer to the manufacturer’s specifications for the correct torque setting.

Step 6 Reattach the Chain

With the new derailleur secured, reattach the chain. If you’ve broken the chain, use your chain tool to connect the links securely. Make sure the chain is threaded through the derailleur’s jockey wheels in the correct order, following the path indicated on the derailleur body.

Step 7 Adjust the Derailleur

To ensure smooth shifting, you’ll need to adjust the derailleur. Shift the bike into the highest gear (largest cog). The derailleur’s limit screws (marked as H or L on the derailleur body) control how far it can move in either direction. Adjust the screws so that the chain can shift smoothly without overshooting the gears.

Step 8 Test Shifting

Before you put the wheel back on, give the pedals a spin to test the shifting. Shift through all the gears to ensure the derailleur is functioning correctly. If any adjustments seem necessary, tweak the barrel adjuster on the derailleur or re-evaluate the limit screws.

Step 9 Reinstall the Wheel

Once everything is functioning smoothly, reattach the rear wheel, ensuring it’s securely in place. This is crucial for your safety and the bike's performance.

Conclusion

Replacing the rear derailleur on your mountain bike can enhance your riding experience significantly. By following these steps, you can either restore or improve the shifting efficiency of your bike. Remember to perform regular maintenance checks and adjustments to keep your drivetrain in top condition. Happy riding!