How to Install a Derailleur on a Bike

The derailleur is the mechanism that shifts the bike chain between the gears, allowing the cyclist to shift up and down smoothly. You can install a new one on a bike fairly directly, though it is trickier than other bicycle repair procedures and requires a little work.

Instructions

Difficulty: Moderate

Things You’ll Need:

• Repair stand
• Grease
• Phillips screwdriver
• Needle-nose pliers

1. Check the reference information on both the bike and the derailleur to see that they are compatible with each other and that the derailleur will work with the set of cogs on your bike when you install it.
2. Secure the bike to the repair stand, making sure it will not twist or wobble while you are working on it. You want the bike in a position where the chain is parallel to the ground or as close as you can reasonably get it.
3. Remove the bicycle chain from the bike. Alternatively, you can simply move it to the smallest chain ring by shifting the bike, though this tends to cause more complications in the procedure.
4. Grease the bolt on the derailleur so that it is properly lubricated.
5. Slide the bolt into position on the bike hanger, fitting the derailleur into position.
6. Rotate the derailleur counterclockwise until you reach the stop tab on the mounting plate or the hanger.
7. Place the bicycle chain over the cassette and through the derailleur. Its position should give the chain enough slack for you to work comfortably.
8. Stand behind the bike and check to see that the guide pulley is lined up to the nearest cog. You can tighten or loosen the screws with a Phillips head screwdriver to move its position. The "H" screw moves it outward, while the "L" screw moves it inward.
9. Pull the derailleur cable through the anchor bolt with a pair of needle-nosed pliers.
10. Tighten the anchor bolt while you hold the cable taut with the pliers.
11. Check to see that the inner wire is still in its groove.
12. Snip or crimp the end of the wire if it sticks out from the mechanism too far. You usually don't want more than 2 or 3 inches extending out beyond the mechanism.
13. Shift gears on the bike to make sure that the derailleur is installed correctly. You may adjust the screws on the derailleur to "fine tune" it as you go.
14. Remove the bike from the repair stand.

Tips & Warnings

• Make sure your work space is well lit when you install a derailleur. Proper lighting is essential to make sure you can properly see what you're doing, especially with delicate work such as this.