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

Chain wont stay on Large Chainring

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.

Chain wont stay on Large Chainring

Old 05-01-10, 01:06 PM
  #1  
mikeyc424
Newbie
Thread Starter
 
Join Date: May 2010
Posts: 1
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Chain wont stay on Large Chainring

I recently purchased a 10 speed Road bike with a full Shimano 105 groupset. I was out riding it today and about half way through my ride I tried to switch to my large chainring and was unable to. The chain would move over to the large chainring, but as soon as I let go of the shifter and continued peddaling it moved itself back to the small chainring again. Also when I shifted to the gear with the most tension on the small chainring my bike bike a sort of clicking and clanking sound . I am unfamiliar with proper terms as this is my first Road Bike. Any advice would be greatly appreciated.
mikeyc424 is offline  
Old 05-01-10, 02:01 PM
  #2  
JiveTurkey
Low car diet
 
JiveTurkey's Avatar
 
Join Date: Aug 2007
Location: Corvallis, OR, USA
Posts: 2,407

Bikes: 2006 Windsor Dover w/105, 2007 GT Avalanche w/XT, 1995 Trek 820 setup for touring, 201? Yeah single-speed folder, 199? Huffy tandem.

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Problem 1: Likely the High ("H") limit screw on the front derailleur (FD) is too tight, preventing the FD from being able to move far enough out. Unscrew it pretty far, then shift to the biggest chainring and smallest cog in the rear (this is the highest gear). While pedaling, screw in the H-limit screw on the FD slowly until you hear rubbing, then back it off a smidge (you may need to test this by downshifting and then upshifting back to the outer chainring).

Problem 2: You're talking about being in the lowest gear (smallest chainring, largest cog), right? It's possible it's the Low ("L") limit screw on the FD, though that would make a rubbing noise, not a click clacky noise. More likely the B-tension screw of the rear derailleur (RD) is not screwed in enough. Screwing in the B-tension screw moves the RD's upper pulley down a bit so there's more clearance to clear the largest cog. While in the lowest gear, turn in the B screw and see if it can go away while pedaling. Having too long of a chain can also exacerbate the problem.

Edit: Sooner or later, you'll likely need to fine-tune your drivetrain. May as well learn about it now and get it performing optimally: http://sheldonbrown.com/derailer-adjustment.html

Also, Park Tool's website has a good instructions on setting up the derailleurs.
JiveTurkey is offline  
Old 05-01-10, 06:23 PM
  #3  
joejack951
Senior Member
 
joejack951's Avatar
 
Join Date: May 2004
Location: Wilmington, DE
Posts: 11,853

Bikes: 2016 Hong Fu FM-079-F, 1984 Trek 660, 2003 Specialized Hardrock, 2004 LOOK KG386i (RIP), 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1, 2016 Islabikes Beinn 20 (son's)

Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 1116 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by JiveTurkey View Post
Problem 1: Likely the High ("H") limit screw on the front derailleur (FD) is too tight, preventing the FD from being able to move far enough out. Unscrew it pretty far, then shift to the biggest chainring and smallest cog in the rear (this is the highest gear). While pedaling, screw in the H-limit screw on the FD slowly until you hear rubbing, then back it off a smidge (you may need to test this by downshifting and then upshifting back to the outer chainring).
Based on the description of how he can hold the shifter and the chain will stay on the big ring, I'm going with too little cable tension. If the high stop screw were set too tight, he wouldn't be able to shift into the big ring at all or he'd just have a chain rub issue. High stop screws generally don't go out of adjustment either so if the bike shifted properly at one point, the only likely cause of the change is loss of cable tension.
joejack951 is offline  
Old 05-01-10, 07:33 PM
  #4  
DX-MAN
Banned
 
Join Date: Jun 2009
Posts: 4,788
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Either of these would be fixes for the problem. Try the limit screw first, it's simpler.
DX-MAN is offline  

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

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