49. How To Install a Rear Derailleur

Removal and installation of a standard bolt-on rear derailleur.

IMPORTANT: Nuts and bolts on your bike should always be tightened to the manufacturer's specifications.
How To Install a Rear Derailleur
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In this tutorial we’ll learn how to replace a standard bolt-on rear derailleur.

Tools

For this job you’ll need a 5mm hex key for the derailleur’s mounting bolt, and a 2.5mm or 3mm hex key for the jockey wheels if you will not be removing the chain to clean or replace it. If you are removing the chain you may need a chain tool depending on your type of chain. You’ll also need wire cutters and a 9 or 10mm metric open end wrench, or a 5 or 6mm hex key to remove and install the rear shift cable. The last thing you’ll need is a phillips (+) screwdriver for adjusting the derailleur’s limit screws.

Rear Derailleur Removal

The first step is to shift your chain onto the smallest rear sprocket. Then pull off the shift cable’s end cap and loosen the cable pinch bolt. Remove the cable from the derailleur.

Now you’ll need to remove the chain from the derailleur. Some chains have a special connector pin that need replacing if removed, so if you don’t need to remove the chain for cleaning or replacement you can simply remove the lower jockey wheel and rotate the cage plate to release the chain. If you are removing the chain, disconnect a link and pull the chain through the jockey wheels.

Now you can unthread the derailleur’s mounting bolt all the way counter clockwise to remove the derailleur.

Rear Derailleur Installation

Before installing the new rear derailleur, apply some waterproof grease to the mounting bolt. Then thread it part way into the derailleur hanger, and rotate it clockwise to make sure the b-screw or tab is sitting behind the flat on the back of the hanger. Then fully tighten the mounting bolt.

If your chain is still on the bike, undo the bottom jockey wheel and thread the chain over the top pulley. Then re-install the lower jockey wheel. If you have removed the chain, re-route the chain through the jockey wheels and reconnect it. Search the site for tutorials on how to use a chain tool or a quick release chain link.

Rear Derailleur Set-up

Now preset the high-limit (H) screw so the upper jockey wheel is roughly in line with the smallest sprocket when viewed from behind.

Thread the shift cable back into the derailleur, pull it tight and tighten the anchor bolt so the cable flattens. Then find a bare stretch of cable and give it a good pull to make sure the cable is seated and has no slack. Then loosen the cable, pull it tight again and re-tighten it.

Now you’ll need to adjust the rear derailleur as shown in previous tutorials. If necessary, trim the cable so there is about 2 inches remaining. Then slide on a cable end cap and crimp it in place.

Tags

Discuss this topic in the Derailleur Forums

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My Cervelo S5 has a rival groupo on it. When it works I love it! Have had it in the shop 3 times and still have problems. I have only had it a month! More often than not the when trying to go from the small ring to the large ring, it won't go.They put it on the stand and it works great! I try to tell em that it is under a load when it happens. They ride it around the parking lot and it does not happen! They think I am a blithering idiot! Yesterday it dropped the chain on a shift from the large to the small ring and took a gouge out of the carbon! I went from aggravation to PISSED in a matter o... Read more >>

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Hello, I'm looking for some help for replacing my derailleurs. It's a pretty old bike; I think it was made mid 90's. Anyhow the rear derailleur has worn out and I was told it's better to buy them in sets of front+rear by a friend. Naturally, we have no idea what we're doing so I've listed my bikes parts as best as I can down below. I'm afraid if I try and buy anything with my lack of know-how that it won't fit or it'll mess with my gear ratio a bunch.
Any assistance in figuring this out would be greatly appreciated.

It's built for a mix of road/mountain biking with thick Nim... Read more >>

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Hi,

While fixing a broken chain, the chain came completely off of my rear derailleur. I fed it back through (in a way I thought was right) and fixed the chain. When I tried riding the bike again, it pedaled smoothly at first but gradually became choppier and then became so slack that pedaling was ineffective.

In trying to figure out what went wrong, I noticed that the arrangement of the rear derailleur pulleys had changed. The first two attached photos show what they look like now. They basically do nothing to support the chain. If I hold the lower pulley back, a... Read more >>

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I got a trainer and I’m using that as a stand to fix my error. But I follow the directions in my manual and have looked at tons of different directions on YouTube, which all seem to be about the same. The damn thing still rubs when in the extreme cogs 8 and 1. The middle crank which I thought would be f... Read more >>

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I have a GT, Nomad 2.0, and this is the same derailleur that's on there. I need a new one because my frame hanger snapped, and the derailleur itself bent in two differnt places.

I'm going to return the derailleur and get the regular/closed hole TX35 derailleur.
I've been looking everywhere for the two parts, the derailleur and frame hanger.
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One: ... Read more >>

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Hi. I had an accident where my bike fell off to the ground. After that, the chain is rubbing the cage of the lower pulley in the rear derailleur. It's making metallic sound, as it rubs against the cage. Heare are some images for you to look. I appreciate you valueable response on how to fix this. I am using Shimano Sora. The images are taken while the bike has been mounted upside down.

[Image: 20140309_120415.jpg]... Read more >>

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