how to install a derailleur on a mountain bike

How to Install a Derailleur on a Mountain Bike

Installing a derailleur on a mountain bike might seem like a daunting task, especially for beginners. However, with the right tools and some patience, you can successfully install a derailleur yourself. In this guide, we'll walk you through the step-by-step process to ensure your gear shifting is smooth and efficient.

Tools You'll Need

Before you begin, gather the necessary tools

1. Allen wrenches (usually 4mm and 5mm) 2. Screwdriver (flathead and Phillips) 3. Chain tool (for adjusting the chain length if needed) 4. Bike stand (optional but helpful) 5. Measuring tape (optional for precise adjustments)

Step 1 Prepare Your Mountain Bike

1. Remove the Rear Wheel To access the derailleur, you must remove the rear wheel. Shift down to the smallest rear cog to relieve tension on the derailleur, then unbolt or disengage the quick-release mechanism to take off the wheel.

2. Remove the Old Derailleur If you're replacing an old derailleur, you'll need to remove it first. Use the appropriate Allen wrench to unscrew the mounting bolt holding the derailleur to the derailleur hanger. Keep the screws and any spacers, as you may need them for the new derailleur.

Step 2 Install the New Derailleur

1. Attach the New Derailleur Position the new derailleur on the derailleur hanger. Ensure that it is oriented correctly, with the jockey wheels positioned below the chain line. Insert the mounting bolt and tighten it securely, but be careful not to overtighten it, as this can strip the thread.

2. Connect the Chain If you're using the same chain, thread it through the new derailleur's jockey wheels following the correct path (usually from above the top jockey wheel and below the bottom one). If you have a new chain, you may need to determine the correct length beforehand, which can be done using the chain's specific length guide or a chain tool.

Step 3 Adjust the Limit Screws

Once the derailleur is installed and the chain is attached, you'll need to adjust the limit screws, which prevent the derailleur from moving the chain too far and falling off the cogs.

1. Set the High Limit Screw Position the chain on the smallest rear cog and the largest front chainring. Adjust the high limit screw (usually marked H) until the derailleur is positioned just above the small cog without making contact.

2. Set the Low Limit Screw Next, shift the chain to the largest rear cog and the smallest front chainring. Adjust the low limit screw (marked L) so that the derailleur shifts freely but doesn't allow the chain to fall off.

Step 4 Cable Installation and Tension Adjustment

1. Attach the Shift Cable Thread the end of the shift cable through the cable anchor on the derailleur. Pull the cable tight and use the Allen wrench to secure it.

2. Set Cable Tension Engage the shifter to shift the derailleur to the smallest cog. Check that there’s no slack in the cable. If there is, use the barrel adjuster (if available) to add tension. A correctly tensioned cable is crucial for smooth shifting.

Step 5 Test the Shifting

With everything installed, it's time to test the shifting

1. Reinstall the Rear Wheel Ensure that the wheel is secured properly and that the chain is in place.

2. Test Shift Through Gears Shift through all the gears while the bike is stationary. Observe if the derailleur moves smoothly between all cogs. If it hesitates or shifts inaccurately, you may need to readjust the cable tension.

3. Fine-Tuning If necessary, fine-tune the limit screws and cable tension until you achieve smooth performance.

Conclusion

Installing a derailleur on your mountain bike may take some practice and patience, but it’s a rewarding skill that can save you money on bike repairs. By following these steps carefully, you’ll be well on your way to ensuring your bike shifts smoothly during your next ride. Remember to regularly check and maintain your derailleur for optimal performance!