how to replace rear derailleur on mountain bike

How to Replace a Rear Derailleur on a Mountain Bike

Replacing the rear derailleur on your mountain bike can seem intimidating, especially if you're not familiar with bike mechanics. However, with a little guidance and the right tools, it’s a manageable task that can enhance your bike's performance. In this article, we’ll walk you through the steps to replace your rear derailleur successfully.

Tools You'll Need

- New rear derailleur - Phillips and flathead screwdrivers - 5mm Allen wrench (or the appropriate size for your derailleur attachment) - Chain tool (if you need to remove the chain) - Bike stand (optional but helpful) - Clean cloth and degreaser

Step 1 Gather Your Materials

Before you begin, ensure you have your new rear derailleur and any necessary tools gathered in one place. It’s essential to choose a derailleur compatible with your bike's drivetrain (Shimano, SRAM, etc.), so double-check the specifications before you purchase one.

Step 2 Prepare Your Bike

If you have a bike stand, place your bike in it to make the process easier. If not, flipping your bike upside down works too. Shift your chain to the smallest chainring and the smallest cog on the rear cassette. This position reduces tension on the derailleur and makes removal easier.

Step 3 Remove the Old Derailleur

Start by locating the screw that attaches the derailleur to the derailleur hanger on the frame. Using the appropriate Allen wrench, loosen and remove this bolt. Be careful to keep the bolt in a safe place; you’ll need it later for the new derailleur.

Next, you will need to detach the derailleur from the chain. If your chain uses a quick link, you can simply split the link using your hands. If not, you may need to use a chain tool to remove a link.

Finally, disconnect the cable that runs to the derailleur. There will be a barrel adjuster at the derailleur housing; unwind this to relieve any tension before pulling it out of the housing.

Step 4 Install the New Derailleur

With the old derailleur removed, take your new derailleur and attach it to the derailleur hanger using the same bolt you removed earlier. Make sure it is seated correctly and tighten the bolt securely, but avoid over-tightening, which can damage the threads.

Once it is attached, route the bike chain through the new derailleur, ensuring it follows the correct path according to the derailleur's diagram. If necessary, use your chain tool to connect any links.

Step 5 Connect the Cable

Next, it’s time to attach the cable. Feed the cable through the barrel adjuster and then into the derailleur. Pull the cable tight and secure it in place. Ensure that the cable is correctly adjusted; you may need to adjust the tension slightly to ensure smooth shifting.

Step 6 Adjust the Limits and Test

Now that your derailleur is installed, you’ll need to set the limits. Adjust the limit screws (often marked as H for high and L for low) to ensure that the derailleur doesn’t move the chain beyond the appropriate gears. Shift through the gears to check for smooth operation.

Step 7 Final Checks

Finally, take your bike for a short ride to test the new derailleur. Pay attention to how it shifts and listen for any unusual sounds. If the shifting isn’t smooth, you may need to re-adjust the cable tension or limit screws.

Conclusion

Replacing the rear derailleur on your mountain bike doesn’t have to be a daunting task. With preparation and patience, you can perform this upgrade or repair on your own. Not only will this save you money, but it will also enhance your bike riding experience. Always refer to your bike’s manual for specific instructions related to your model, and happy cycling!