how to change a derailleur on a mountain bike

How to Change a Derailleur on a Mountain Bike

Changing a derailleur on a mountain bike may seem daunting, but with the right tools and a bit of patience, it's a manageable task for any bike enthusiast. The derailleur is an essential component of the bike's drivetrain, responsible for shifting the chain between gears. Whether your derailleur has sustained damage, worn out over time, or you’re upgrading to a better model, this guide will walk you through the process step by step.

Tools and Materials Needed

Before you begin, ensure you have the following tools at your disposal - 5mm Allen wrench or screwdriver (depending on your derailleur) - Chain tool (if needed to break the chain) - New derailleur - Lubricant - Clean cloth - A bike stand (optional but helpful)

Step 1 Prepare Your Bike

Start by finding a suitable workspace. If you have a bike stand, place your bike in it, allowing for easier access to the derailleur. If a stand isn’t available, simply flip your bike upside down. Ensure your bike is clean to minimize dirt entering the components during the process.

Step 2 Remove the Chain

If your new derailleur requires you to remove the chain, use a chain tool to separate the links. However, many derailleurs can be replaced without removing the chain. If you can avoid it, this will save you time, as re-threading the chain can be cumbersome.

Step 3 Disconnect the Derailleur

Locate the mounting bolt that secures the derailleur to the derailleur hanger (the metal piece extending from the frame). Use your 5mm Allen wrench or screwdriver to loosen this bolt. Once it’s loose, you can lift the derailleur off the hanger.

Next, you will need to disconnect the cable that controls the derailleur. Use your Allen wrench to loosen the bolt securing the cable, and then pull the cable out. Be careful not to lose any parts during this process.

Now it’s time to install your new derailleur. Position it on the derailleur hanger where the old one was located. Secure it using the mounting bolt, tightening it sufficiently without over-torquing, as this can strip the threads.

Next, thread the cable through the derailleur’s cable housing and pull it tight. Once in position, tighten the cable bolt to secure it. Ensure the cable is positioned correctly in the derailleur’s pulley system.

Step 5 Adjust the Limit Screws

Limit screws are crucial as they define how far the derailleur can move the chain toward the smallest and largest cogs. Locate the two limit screws labeled “H” (high) and “L” (low) on the derailleur.

- Adjust the High Limit Shift your chain onto the smallest chainring and the smallest rear cog. Adjust the “H” screw until the derailleur is aligned with this cog. This prevents the chain from overshifting off the smallest cog. - Adjust the Low Limit Shift to the largest chainring and the largest rear cog. Adjust the “L” screw until the derailleur is positioned perfectly in line with the largest cog. This prevents the chain from shifting off the other end.

Step 6 Fine-Tuning the Shifting

After setting the limit screws, slowly test the gearing. Shift through the gears to check for any misalignment or skipping. If you notice that the chain isn't shifting smoothly, fine-tune the barrel adjuster located on the derailleur or the shifter. This adjustment can help fine-tune cable tension for optimal performance.

Step 7 Check Everything and Test Ride

Finally, double-check all connections and ensure the derailleur is securely attached. Clean any excess lubricant and debris from the drivetrain. Once you feel confident in your work, take your bike for a short test ride. Shift through all gears to ensure everything functions smoothly.

Conclusion

Changing a derailleur on a mountain bike is a straightforward process that can save you time and money. With just a few tools and these step-by-step instructions, you can effectively replace your derailleur and ensure your bike rides like new. Happy cycling!