Rear derailleur problem

randomstuff

I recently cleaned out my rear derailleur, after replacing the chain the lower 'arm' of the derailleur isn't tight, seems like its lacking some spring tension.

Which bolt do I need to tighten to get it correct?

Also the chain seems to be skipping, whenever I moderately push on the pedals while pedalling

I've attached a picture to better explain my problem...

Its a Campagnolo Athena triple, if it matters.

http://imgur.com/yGg4Alm

http://imgur.com/zPBiBAu


Thanks

crosstownk

You might have a broken/displaced spring in the derailleur. There doesn't appear to be much tension on the chain.

randomstuff

crosstownk wrote: »

You might have a broken/displaced spring in the derailleur. There doesn't appear to be much tension on the chain.

How would i go about figuring it which it is? I'm quite sure i put it back on same way as i took it off

crosstownk

You'll need to look for the spring and its seats and see if you can replace the spring to its correct position.

randomstuff

crosstownk wrote: »

You'll need to look for the spring and its seats and see if you can replace the spring to its correct position.

Does this randomly happen? While cleaning the derailleur I didn't disassemble it.

bcmf

Have you screwed the mech back into the frame wrong. Is there a stop knurl on your frame where the mech sits against. It looks like its screwed in wrong.
Have you put on a new chain? If so is it the same lenght as the old one?
Have you changed your cassette as well? If not then this would explain your skipping.

smacl

Agree with BCMF, rear mech seems rotated towards the front. If you look at the side on photo, the arm is pointing ~45 degrees to the front of the bike. For the middle ring on a triple and the cog you're in, it should be pointing ~20 degrees towards the back of the bike. Looking at the first picture, the chain barely goes near the first jockey wheel. I'm running a campag veloce triple, which is a similar enough mech, and the same gear combo is shown below. It could also be that you have the cable far too short, as it is the cable that brings the arm forward, and the spring that brings it back. I'd start by disconnecting the cable and seeing if the arm fully retracts, if not the derealluer is rotated.

randomstuff

bcmf wrote: »

Have you screwed the mech back into the frame wrong. Is there a stop knurl on your frame where the mech sits against. It looks like its screwed in wrong.
Have you put on a new chain? If so is it the same lenght as the old one?
Have you changed your cassette as well? If not then this would explain your skipping.

Yes my frame does have a stop knurl, and I have mounted the mech back as it was.

I did put a new chain on, adjusted its length correctly with the old chain. Didn't change the cassette as it doesn't seem worn

After looking at diagrams of the rear mech, it seems like the secondary spring in the extending arm has become too soft.

randomstuff

smacl wrote: »

Agree with BCMF, rear mech seems rotated towards the front. If you look at the side on photo, the arm is pointing ~45 degrees to the front of the bike. For the middle ring on a triple and the cog you're in, it should be pointing ~20 degrees towards the back of the bike. Looking at the first picture, the chain barely goes near the first jockey wheel. I'm running a campag veloce triple, which is a similar enough mech, and the same gear combo is shown below. It could also be that you have the cable far too short, as it is the cable that brings the arm forward, and the spring that brings it back. I'd start by disconnecting the cable and seeing if the arm fully retracts, if not the derealluer is rotated.

Yes the upper jockey wheel barely touches the chain. Does the cable tension adjust the tension of the secondary arm also? Or just the main mech body?

bcmf

The cable just places tension on the body. The jockey wheels take the tension on the chain.

randomstuff

bcmf wrote: »

The cable just places tension on the body. The jockey wheels take the tension on the chain.

What dictates the tension on the extending arm? Is there an adjuster for that?

smacl

randomstuff wrote: »

Yes the upper jockey wheel barely touches the chain. Does the cable tension adjust the tension of the secondary arm also? Or just the main mech body?

If you disconnect the cable entirely, the spring should be strong enough to take up all the slack on the chain. If you put the front into the middle ring and spin the pedals without the cable connected, the chain should end up on the smallest sprocket in the cassette. If this doesn't happen you've a problem, possibly with the spring or maybe just grit in the mech. If it does work ok, I'd tend to go through the steps in the campag rear DR set-up notes.

Note, I'm not a bike mechanic so the above advice is entirely amateur based on experience, but have just recently replaced my own rear mech.