How to Change Your Rear Derailleur - Replacing Your Bike's Rear Mech

Replacing and adjusting your rear derailleur to make sure that your gears are shifting correctly is a relatively easy task when you know how.

Key in moving the chain up and down the cassette, rear mechs are pretty sturdy, but can over time stop working as well as they once did, or if you're a mountain biker get ripped off entirely by rocks or roots.

Here we show you how to change your rear derailleur and how to adjust it so that it shifts correctly, using the H, L and B screws. We also look at fine tuning the shifting with the use of the barrel adjusters to sort the indexing of your gears.

Music:

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Music licensed by Cue Songs
Music - licensed by Cue Songs

[JeremyDuckArt]

Thanks. I've done it successfully. Went into my LBS for a chainlink connector and cable crimps, told the guy what I was doing, he wasn't very happy as he's being doing all my repairs for a number of years now, I've not often been happy with the standard of his work, but now I can do some of it myself, that's just great.

[TheLionEric]

I typed this list of instructions I took down from the video. It's word for word what we just listened to so up vote this so we have both options when you make it out to your garage.

1. Undo Chain
2. Detach cable from rear mech, pull out cable
3. Unscrew main rear mech bolt
4. Screw in new rear mec, watch for cross threading
5. Tighten B tension screw behind the stop on the hanger should be 1 cm from top jockey wheel and big sprocket
Removing Cables
6. Gear down
7. Roll back rubber lever cover and remove cable
8. Insert Cable through the same cable guides etc the original came from
9. Screw the barrel adjuster in entirely and turn it back one rotation
10. Tighten the crimp bolt on the rear mech onto the cable, having pulled the cable tight
11. reattach chain
12. (Chain position Smallest cog in the rear and biggest ring in the front) Align the jockey wheels to the smallest cog using the H screw. Screw clockwise to move towards bigger cogs.
13. (Swap to biggest cog small ring, if you cant get into the big cog its either lack of cable tension or the L screw push down on the mech/pull cable to test the tension first) Use L screw to align rear mech jockey wheel to the big cog
14. Adjustments - starting from the big cog try to gear into your small cogs. If it doesnt shift smoothly try loosening the barrel adjuster. Adjust till you're satisfied.
15. Cut the cable leaving one inch of cable hanging out and add on a cable end cap and crimp it on.

[The_BenD]

When listing the needed tools it sounded like you said "a chainsaw" rather than "a chain tool"

Caught me off guard for a second there lol

[richardplastino]

Well, I just spent about 8 hours over 3 days trying to figure out why I could not adjust the derailleur. Maybe he said it in this video, but I did not hear it. Before you tighten the derailleur, or mech as he calls it; it must first be rotated as far as possible to the rear of the bike, then tighten it. Dumb yes, but who knew the first time? I can see now that he's holding it in the rear position, but that was not obvious until I found my own error.

[leemoore]

I wish we could all have the same standard when it came to what "lowest gear" means. At 1:55, Dan talks about shifting to the "lowest gear, " but the video shows him shifting to the smallest cog, which I would generally call the "highest gear" (since it's the highest gear ratio).

[michaelroberts]

I can't even begin to tell you how good this video is! I think you answered about 27 of my questions in less than 6 minutes! Thank you!

[WayneWBishop]

Fantastic video. Very detailed and thorough! Looking forward to following these instructions as I work on the bike this weekend.

[herrhero]

Thanks guys for this video. I was struggling for hours trying to get the gears to downshift with a replacement medium cage (to cater for the 32 cassette) SRAM Force 22 setup. This video mentions replacing frayed / old cables so I reluctantly due to the internal routing replaced the cable and now it works like a dream. The old cable was getting was caught up inside the sheath and not allowing the derailleur to freely move.

[NoodleAWA]

I'm just starting a RD replacement and this has cleared up all the bits I was shaky about. Thanks!

[daveb]

There is something very satisfying about doing your own bike repairs. GCN is a massive help. Have a go, its not rocket science!!

[ThePeterfrancon]

Trashed my rear deraillieur - large twig incident, found a replacement and your video has shown me how to set it up! Thanks indeed!

[christianideryd]

I used the tips in this video when i replaced my rear derailleur. Everything works fine! Easy to follow your guidelines

[MrTCakebread]

Best description yet on changing and setting up rear derailleur that I have seen. Well done guys. Typed instructions from you would be even better. Thanks

[Dartsu]

have to say thanks GCN, Having recently bought a new bike with cheapish parts, through the guidance on these videos I have managed to replace almost all the mechanical parts on my bike to ultegra+DA :D

[jorgearreola]

I just wanna say thank you so much for this tutorial! You did fantastic .I'm a rookie at working on bikes so I had quite the struggle replacing my derailleur. Thanks to your video I was able to manage. I had no clue on how to adjust it prior to your video.

[davidt]

Just set up my first 1 x12 drivetrain. This vid has helped no end. One more subscriber here

[horseshoe_nc]

Thank you for this video. I have a mountain bike that needs a new rear mech. This video will be a big help. My main concern was adjusting the new mech. I now know it should be fairly straightforward.

[pallarisari]

fantastic, just setup my rear derailleur that 2 mechanics fail to complete effectively. Fantastic advice and keep these great guides coming. My Trek Madone is feels silky smooth when shifting

[frankparrish]

Best tutorial on rear derailleur replacement and adjustment. Thanks!

[stephenm]

Fantastic videos as always. They certainly beat the service from any of the cycle shops in Aberdeen