Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Rear derailleur sometimes jumping sprockets

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Rear derailleur sometimes jumping sprockets

Old 08-12-20, 09:31 PM
  #1  
kaiserschmarrn
Senior Member
Thread Starter
 
Join Date: Apr 2020
Posts: 134
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 41 Post(s)
Liked 9 Times in 8 Posts
Rear derailleur sometimes jumping sprockets

I am ok with installing and adjusting front derailleurs, but have never messed with rear derailleurs. I have found an intermittent issue with the rear derailleur. Sometimes when I am on the third gear from the top, then go to switch to the next gear, it makes two shifts at once, putting me in the highest gear. What adjustment is likely out and causing this?

Thanks,

Danny

Last edited by kaiserschmarrn; 08-12-20 at 09:54 PM.
kaiserschmarrn is offline  
Old 08-12-20, 09:38 PM
  #2  
trailangel
Senior Member
 
trailangel's Avatar
 
Join Date: Feb 2014
Location: Pasadena, CA
Posts: 4,250

Bikes: Schwinn Varsity

Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 1576 Post(s)
Liked 294 Times in 187 Posts
Bent DR hanger
trailangel is offline  
Likes For trailangel:
Old 08-13-20, 09:13 AM
  #3  
jadocs
Senior Member
 
jadocs's Avatar
 
Join Date: Jul 2018
Location: USA
Posts: 1,659

Bikes: Ti, Mn Cr Ni Mo Nb, Al, C

Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 721 Post(s)
Liked 336 Times in 224 Posts
Or cable tension
jadocs is offline  
Old 08-13-20, 09:20 AM
  #4  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,278 Times in 798 Posts
side effect of all the engineering to make it shift faster..
fietsbob is offline  
Old 08-13-20, 09:23 AM
  #5  
natloz
Senior Member
 
Join Date: Jun 2020
Location: Alberta, Canada
Posts: 156

Bikes: Bianchi Alfana, Specialized Hardrock, Specialized Sirrus Pro SS Conversion

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked 48 Times in 33 Posts
Originally Posted by kaiserschmarrn View Post
I am ok with installing and adjusting front derailleurs, but have never messed with rear derailleurs. I have found an intermittent issue with the rear derailleur. Sometimes when I am on the third gear from the top, then go to switch to the next gear, it makes two shifts at once, putting me in the highest gear. What adjustment is likely out and causing this?

Thanks,

Danny
To me it sounds like your indexing is off. Once you set your upper and lower limits you can shift up onto the 3rd from the smallest ring and if it is not smooth you adjust the barrel adjuster at the derailleur to get the indexing dialed in. I will twist it until it shifts and then dial it back to be quiet. Test between shifting back and forth between the 3rd and 4th smallest rings, once that is good, then try the entire range. If the indexing is slightly off, it will be jumpy as the chain can partially ride up another ring or down onto another ring.
natloz is offline  
Old 08-13-20, 10:04 AM
  #6  
kaiserschmarrn
Senior Member
Thread Starter
 
Join Date: Apr 2020
Posts: 134
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 41 Post(s)
Liked 9 Times in 8 Posts
Originally Posted by jadocs View Post
Or cable tension
Too much tension, maybe?

Danny
kaiserschmarrn is offline  
Old 08-13-20, 10:54 AM
  #7  
cyccommute 
Mad bike riding scientist
 
cyccommute's Avatar
 
Join Date: Nov 2004
Location: Denver, CO
Posts: 22,923

Bikes: Some silver ones, a red one, an orange one and a few titanium ones

Mentioned: 113 Post(s)
Tagged: 1 Thread(s)
Quoted: 3476 Post(s)
Liked 946 Times in 587 Posts
Originally Posted by kaiserschmarrn View Post
Too much tension, maybe?

Danny
Probably. Shift to the lowest tension which is usually the highest gear (smallest cog on the back). Check the tension on the cable by plucking it. It should have a little bit of twang but it shouldn’t be as tight as a guitar string. Most of the time the cable is too slack...indicated by being able to pull it away from the frame...but sometimes it is too tight. If it is “twangy”, back off on the barrel adjuster on the rear derailer or on the shifter or frame (depending on what kind of shifter you have). Then run the bike through the gears. One click should move the derailer on gear.

If that doesn’t work, you might have some issues with the outer cable. It might be dragging on the inner cable causing too much tension. Shift the bike to the lowest gear (largest cog, again assuming regular “high normal” derailer). (The pictures below are for a mountain bike but works for road bikes too)

Library - 3391 by Stuart Black, on Flickr

Now, without pedaling, shift up which releases tension on the cable

Library - 3392 by Stuart Black, on Flickr

This will make the cable very slack

Library - 3393 by Stuart Black, on Flickr

You should be able to pull the cable out of the frame

Library - 3394 by Stuart Black, on Flickr
Library - 3395 by Stuart Black, on Flickr

and pull it away from the shifter as well. Put a little grease on your thumb and forefinger and run it up and down the inner cable. Lubricate anything that is under the outer cable.

While you have the cable slack, inspect the ends of the cable and see if there are any wires poking out of the ferrule like this

IMG_1361 by Stuart Black, on Flickr

If there are, this means that the outer cable probably needs replaced since the rods in the outer cable have come loose. The loose wires will cause the inner cable to jam. You should be able to pull most ferrules off the cable housing to look for this kind of stucture

IMG_1362 by Stuart Black, on Flickr

Cable tension and cable lubrication are usually the problem. That should cover 99% of all issues. If that doesn’t work, check the derailer hanger...you can eyeball it to see if the cassette, upper wheel and lower wheel line up. But it’s usually the cable.
__________________
Stuart Black
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Days of Wineless Roads. Bed and Breakfasting along the KATY
Twisting Down the Alley. Misadventures in tornado alley.
cyccommute is offline  
Likes For cyccommute:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.