# Bicycle Mechanics - chain/shifting problem revised

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View Full Version : chain/shifting problem revised

06-05-07, 08:29 AM
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?

Al1943
06-05-07, 11:17 AM
"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

06-05-07, 07:27 PM
[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:)