Chain impacting (not grinding/rubbing) on front derailleur

BDFun

Hi,

When I hit bumps in the road, my chain will hit the top of the derailleur (circled in picture below):


I remember this happening after a few weeks of cycling when I first bought the bike and it was remedied as part of the free service I got from the LBS. It is only very mild at the moment but it will get worse like it did last time.

Why do I think it is the chain hitting the derailleur at that point? If I try to reproduce the problem by dropping the back end of the bike by a couple of inches, I can see the chain moving into it and there is quite a bit of lubricant on the upper part of the derailleur (where I've circled).

I'm not too sure what I need to adjust, as gears to me seem pretty sensitive to any adjustment.

Much appreciated if someone could help me.

thel33ter

Undo the band, and move the mech up a bit, it looks way too low.

John.T

It is stopping the chain from jumping off so leave well alone. The lower edge of the cage should be about 2mm above the big chainring when the chain is on it. If less then raise it. Be sure to re-adjust the cable. If not then ignore it.

BDFun

I don't think it is to do with the mech assembly slipping down the stem because I would be able to see the mark on the stem.

This has only started happening since a couple of days ago. It also happened after I bought my bike and was fixed as part of my free service which involved tuning everything up due to things slackening.

Is it possible that the chain is too slack? If so, how do I increase the chain tension?

Thanks

John.T

Is it possible that the chain is too slack? If so, how do I increase the chain tension?

Very unlikely. Chain tension is set in the mech to cover the range of gears that it is designed for. It is also not likely to change much.
When pedaling the chain tension at the top is set by how hard you are pushing. The clearance between the chain and front mech depends on what gear you are in.
Check the mech installation is correct as in the Shimano doc.
http://cycle.shimano-eu.com/media/techdocs/content/cycle/SI/SI_5GR0A_001/SI_5GR0A_001_En_v1_m56577569830614926.pdf
If so then leave it. I do not think it is anything to worry about. The oil probably gets there from normal gear changing and the noise may not even be coming from there. Try stuffing a small piece of cloth in the gap and do the drop test again.

BDFun

Thanks for your advice John.

I could see the chain hitting that part of the derailleur. I shall try stuffing something into that gap to be sure that is the source of the noise.

BDFun

Just checked, it's definitely the chain impacting the top of the derailleur on bumps. Quite an annoying clacking sound but I don't know what to adjust to correct it.