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 06-05-07, 07:29 AM   #1
fadetoblack6902 
Senior Member
Thread Starter
 
Join Date: Aug 2005
Bikes:
Posts: 370
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
chain/shifting problem revised

specialized sirrus elite with tiagra components, trigger shifters

While in the largest 2 cogs and the middle chainring, if you pedal backwards the chain jumps off the cogs at the top down to smaller cogs. It is not a stuck link. both derailleurs are adjusted perfectly.

When the front derailleur tension is correctly adjusted, in the middle chainring and large cog the chain will not stay on the middle, it willl fall down to the smallest chainring. It has to be overtensioned to stay on the middle ring.

the front shifter seems to have 4 clicks. going up from the small ring, you have to click twice to get to the middle ring. the first click just moves it a little bit. then once its on the middle ring it still has one more click to get to the large ring. Shifting is perfect on the front until it falls off the middle ring.

any ideas?
fadetoblack6902 is offline   Reply With Quote
Old 06-05-07, 10:17 AM   #2
Al1943
Senior Member
 
Join Date: Feb 2005
Location: Oklahoma
Bikes: Trek 5500, Colnago C-50
Posts: 9,433
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
"While in the largest 2 cogs and the middle chainring, if you pedal backwards the chain jumps off the cogs at the top down to smaller cogs. It is not a stuck link. both derailleurs are adjusted perfectly."

Don't pedal backwards.

"When the front derailleur tension is correctly adjusted, in the middle chainring and large cog the chain will not stay on the middle, it willl fall down to the smallest chainring. It has to be overtensioned to stay on the middle ring."

If it's not a tension problem then it must be a chainline problem or a bent chainring. Are you sure you have the correct bottom bracket? It's possible to measure the chainline position of the middle ring from the center of the axial plane of the frame. See Sheldon Brown for chainline info.


"the front shifter seems to have 4 clicks. going up from the small ring, you have to click twice to get to the middle ring. the first click just moves it a little bit. then once its on the middle ring it still has one more click to get to the large ring."

This is normal for a Shimano road triple. You should be able to shift from the smallest chainring to the middle with one sweep of the brake lever, but it requires going to the second clickstop position.
Does it shift to the big ring OK?

Al
Al1943 is offline   Reply With Quote
Old 06-05-07, 06:27 PM   #3
fadetoblack6902 
Senior Member
Thread Starter
 
Join Date: Aug 2005
Bikes:
Posts: 370
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
[QUOTE=Al1943]"While in the largest 2 cogs and the middle chainring, if you pedal backwards the chain jumps off the cogs at the top down to smaller cogs. It is not a stuck link. both derailleurs are adjusted perfectly."

Don't pedal backwards.

I guess that works.

"When the front derailleur tension is correctly adjusted, in the middle chainring and large cog the chain will not stay on the middle, it willl fall down to the smallest chainring. It has to be overtensioned to stay on the middle ring."


If it's not a tension problem then it must be a chainline problem or a bent chainring. Are you sure you have the correct bottom bracket? It's possible to measure the chainline position of the middle ring from the center of the axial plane of the frame. See Sheldon Brown for chainline info.

I did not have this problem the last time it was touched, its been sitting in the basement for a month since I tuned it. It is the factory bb, so that cant be the problem. It does seem like a fairly angled chainline though. The chainring didn't look bent, but i didnt look that closely. It shouldn't be.


"the front shifter seems to have 4 clicks. going up from the small ring, you have to click twice to get to the middle ring. the first click just moves it a little bit. then once its on the middle ring it still has one more click to get to the large ring."

This is normal for a Shimano road triple. You should be able to shift from the smallest chainring to the middle with one sweep of the brake lever, but it requires going to the second clickstop position.
Does it shift to the big ring OK?

I knew this was normal for a shimano road triple, but on most i've seen going back down to the small chainring takes two clicks; this one only takes one and then it has an extra useless one.

Thanks for the help
fadetoblack6902 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 09:57 AM.