Guide / Tutorial - How to adjust rear derailleur screws | Squat the Planet

Guide / Tutorial How to adjust rear derailleur screws

ali

Well-known member
Joined
Aug 9, 2020
Messages
380
Reaction score
1,379
Location
Taiwan
This is a tiny little diagram that saved my ass when i had it downloaded to my phone and my bike chain started to act wonky and fall off the end of cassette while i was switching into the top or bottom gear. There are many websites that tell you how to tune your rear derailleur, but in my experience they are hard to understand when you are stuck on the side of the road with a busted bike. This picture shows exactly what happens when you adjust the screws, no more, no less.

rear-derailleur-w.jpg


You want to adjust it so that the chain comfortably slots into the biggest cog (uphill gear) and smallest cog (downhill gear) when you adjust the gear lever(s) at the front. Once you have adjusted it so the derailleur can push the chain all the way into the top and the bottom without it falling off the end, then you can twist the tension adjuster on the cable one way or the other to make the lever(s) switch cleanly between the cogs in the middle (try one direction first, and if it gets clunkier, try the other direction).

You can also use these trim screws to only use a subset of the cogs, e.g. if your cassette has 7 cogs, but your gear lever only has 6 settings, you can choose which 6 adjacent cogs to use depending on if you want to go uphill more or downhill more.
 

The Toecutter

The Patron Saint of Filth
Joined
Oct 2, 2022
Messages
173
Reaction score
271
Location
Everywhere and nowhere
If your bike also has a front derailleur, the information pertaining to screw adjustment also applies, except it is the left/right(or low/high) limits on the front derailleur that are now being set with the screws. Usually, the derailleur whether front or rear has the letters "L" and "H" indicated next to the screws to let you know which screw is for the "low" gear and which is for the "high" gear.

If no amount of adjustment gets the shifting right, it is possible you could have an issue with the cable tension or the chain itself. As chains wear out, they no longer shift the same as they once did. They can hesitate to go into the largest cog while downshifting. If the cable has any moisture in it, cold weather can even lock the cable into place by freezing the trapped water. Cable housings can also get clogged with dirt and/or degrade from moisture releasing rust, which will require cable housing replacement.
 
  • Like
Reactions: laughingman

laughingman

Well-known member
Joined
Jul 23, 2022
Messages
107
Reaction score
220
Location
Williamsburg PA
Website
www.youtube.com
Hello all. I used more or less this exact same diagram to adjust the derailleur stops when I was learning how to do it as a professional. It can be hard to understand a verbal or written description until you see or do it in person. Its one of the nice things about bikes, all the pieces are visible. If something brakes you can see what it is and how to fix it.

To add a bit to this discussion. Often times when derailleur systems come out of alignment It's not the adjustments or the derailleur at all. Its the derailleur hanger. The spot where the derailleur is attached to the bike is deliberately made soft and malleable. The idea is to save the frame and derailleur if it derailleur gets snagged on something as you ride. This however means that if can get bent out of alignment very easily. Often times just by leaning the bike onto something. Lifting it into a rack incorrectly. Snagging it on your pant leg when your moving it around. If your derailleur hanger is out of alignment, all of your derailleur and cable adjustments are suddenly not in the right spots. But instead of fiddling around with them you can by hand bend your hanger back into alignment. Or ideally use a hanger alignment tool, which bends the hanger to be square to the back wheel in 3 detentions. Often times as a wrench working in a shop if someone brings there bike in with shifting problems you would just pop the derailleur off, align the hanger, Then install the derailleur again and run the gears. 9 times out of 10 it would have solved the problems.

Cable and housing problems are often caused by being left out in the weather. Most housing holds water agents the steel cable in a way that causes rusting. If your building a new bike or replacing your cables. A few dollars more can get you stainless steel cables which are very nice for preventing this. If you are using rim brakes spring for compression-less brake housing. It will give you a lot stronger breaking response.
 
  • Useful
Reactions: The Toecutter

About us

  • Squat the Planet is the world's largest social network for misfit travelers. Join our community of do-it-yourself nomads and learn how to explore the world by any means necessary.

    More Info

Help us pay the bills!

Total amount
$10.00
Goal
$100.00

Latest Library Uploads