Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

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.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 09-04-11, 11:31 AM   #1
Anonymoose
Senior Member
Thread Starter
 
Anonymoose's Avatar
 
Join Date: Jul 2011
Location: NYC
Bikes:
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
FD big ring troubles

This is a '79 Fuji Grand Tourer btw. I'm having serious trouble shifting from the small ring to the big ring. I've followed Park's derailleur adjustment guide and I have adjusted gears on other bikes without trouble before this one. The issue is the shift from the small to the big ring is very slow if at all. If I adjust the limit screw out to the point where it throws the chain the shift is still just as bad, it just culminates with the chain being thrown. This FD is different than my other bikes in that when the cable is slack the derailleur shifts to the big ring (and yes the cable is totally slack when shifting to the big ring). There is a wobble in the crank but the shift from the large to the small cog is crisp and precise so i'm doubting that is the issue but maybe i'm mistaken. I've also tried lubing the spring in the FD to no avail. Anyone have any ideas? This is driving me nuts.
Anonymoose is offline   Reply With Quote
Old 09-04-11, 12:05 PM   #2
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Bikes: Several, mostly not name brands.
Posts: 16,453
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 91 Post(s)
I suspect you have too much friction in the system. Is there a section of housing on the cable where it leads to the derailleur? Often the dependent loop of this housing collects moisture and eventually rusts, causing increased friction and poor shifting. You can try dripping oil into the housing to loosen things up, but often replacement (with a modern, plastic-lined housing and cable) is the best solution.
JohnDThompson is offline   Reply With Quote
Old 09-04-11, 12:46 PM   #3
bikeman715
Senior Member
 
bikeman715's Avatar
 
Join Date: Mar 2008
Location: Salinas , Ca.
Bikes: Bike Nashbar AL-1 ,Raligh M50 , Schwinn Traveler , and others
Posts: 2,419
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Is the chainline ok ? If the BB axle is to long ,(moving the chainrings to far from the frame ) then the FD can not reach (make the shift ) . yes check the housing and replace if needed to .
bikeman715 is offline   Reply With Quote
Old 09-04-11, 02:13 PM   #4
Anonymoose
Senior Member
Thread Starter
 
Anonymoose's Avatar
 
Join Date: Jul 2011
Location: NYC
Bikes:
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Chainline looks fine and the BB crank arms and chainrings are original. I hadn't thought of the cable housing. I've got some extra laying around that i'll try.
Anonymoose is offline   Reply With Quote
Old 09-04-11, 03:48 PM   #5
dsbrantjr
Senior Member
 
dsbrantjr's Avatar
 
Join Date: Sep 2010
Location: Roswell, GA
Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta
Posts: 4,587
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 60 Post(s)
Anonymoose: Don't confine you inspection to the housing; rusted/corroded or frayed inner wire, especially inside the lower housing run, will cause problems. You mentioned lubing the derailleur spring, how about the pivot points? Pull the exposed inner wire like drawing a bow; does the derailleur move freely by hand and return quickly and smoothly to the limit screw via the spring?
dsbrantjr is offline   Reply With Quote
Old 09-04-11, 05:09 PM   #6
Anonymoose
Senior Member
Thread Starter
 
Anonymoose's Avatar
 
Join Date: Jul 2011
Location: NYC
Bikes:
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I switched out the stem shifters for dt suntour powershifters recently but like a dope did not switch the cable housing (the cables themselves are new) out at the bottom so I will definetly check that when I get home.
Anonymoose is offline   Reply With Quote
Old 09-04-11, 05:26 PM   #7
FBinNY 
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Posts: 29,685
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 232 Post(s)
Quote:
Originally Posted by Anonymoose View Post
This FD is different than my other bikes in that when the cable is slack the derailleur shifts to the big ring (and yes the cable is totally slack when shifting to the big ring).
If I'm reading you correctly, you're FD is reverse sprung, meaning the cable pulls it down to the inner ring, and the spring returns it to the outer. If that's correct, you have very few options. Nothing you do with the cable or housing will help since the cable doesn't control this shift. Focus on making sure the FD can move freely and crisply under the spring, then the alignment will be key.

I've found that often rotating the FD so the cage is slightly (not more than slightly) tail out can help the shift to the outside, though it makes trimming more difficult.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline   Reply With Quote
Old 09-04-11, 06:27 PM   #8
Anonymoose
Senior Member
Thread Starter
 
Anonymoose's Avatar
 
Join Date: Jul 2011
Location: NYC
Bikes:
Posts: 181
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
You are correct about the reverse sprung fd and I did align it tail out briefly but found it was even more apt to throw the chain. I'll try to fiddle more with the alignment and lube in case it is getting hung up returning to slack.
Anonymoose is offline   Reply With Quote
Old 09-04-11, 07:05 PM   #9
noglider 
aka Tom Reingold
 
noglider's Avatar
 
Join Date: Jan 2009
Location: West Village, New York City
Bikes: too many
Posts: 27,128
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 240 Post(s)
You may be able to prevent the chain-throwing with the limit screw. I almost always adjust FD's with a little tail-out.
__________________
Tom Reingold, noglider@pobox.com
New York City and High Falls, NY
Blogs: The Experienced Cyclist; noglider's ride blog

Please email me rather than PM'ing me. Thanks.
noglider is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -6. The time now is 03:40 PM.