Slack chain on small ring.

insinkerator

I did a search (boards + google) and I can't seem to find a definitive answer, or at least one that I understand.

Basically, if I'm in the big ring, I can shift through all the cogs and have no issues with chain slack, bar the smallest cog if I suddenly pedal backwards (which is fine apparently?)

However, if I shift into the small ring, all of a sudden the chain gains a whole load of slack, and starts to hang down dangerously close to the ground, and if I freewheel, it crumples on top of itself up on top too. My very basic bike mechanic skills would lead me to believe that for some reason the RD isn't pulling back far enough, and therefore the chain is slack - I can manually pull back the RD and the slack issues goes away.

Is there something that I need to tighten/loosen/oil? Bike is a year old.

In the process of uploading a video of everything I have outlined to youtube, and will edit the link into the OP when it's finished.

EDIT:http://www.youtube.com/watch?v=m1Y2d4odA6I&feature=youtu.be

Thanks in advance for any help

Lumen

Assuming you have the correct cage length rear derailleur for your gearing, it might be that your chain is too long.

Stick it in big-big and see how much slack there is in the rear derailleur.

insinkerator

It's fairly taut in big/big. Not too much room for movement at all.

Here's the video

EDIT: Sorry, the chain is taut, you said the RD. I can move the pulley cage forward/up by about an inch and half..

Unregistered.

Stick up a pic/vid of big-big.

insinkerator

Lumen

I'm a fairly hapless mechanic myself, but it looks like the return spring in the RD isn't doing its job properly.

Unregistered.

insinkerator wrote: »

Doesn't look like the chain is too long, given the position of the dérailleur. Could be the return spring.

insinkerator

Return spring, OK. What does that mean? Does it need to be replaced/tightened/oiled?

C3PO

I had a similar problem recently and the issue was in the freehub!

Lumen

insinkerator wrote: »

Return spring, OK. What does that mean? Does it need to be replaced/tightened/oiled?

Blast it with WD40?

Might also be a sticky cable, so disconnect the cable from the mech and see if that helps. You won't be able to shift but you can move the mech by hand and see if it returns.

lescol

The tension spring is likely snapped!

http://autobus.cyclingnews.com/tech/fix/?id=howfix_deroh shows the innards of a rear derailleur. You might want to take it back to the shop if it's only a year old as there is probably a three year warranty on the rear derailleur.