Why is my chain rubbing against my front derailleur?

[PaulB]

Was working fine until last week when I noticed that when I move over to the smallest 4 sprockets and I'm on the inner chainring, the chain rubs on the derailleur. Why? It's driving me mad as I can't fathom out why. I've loosened off the cable tension and gone right through the adjustment screws but to no avail. Why oh why am I being tormented like this?

Seriously, anyone got any ideas?

 

[fossyant]

Adjust the limit screw ?

Could you have knocked and mis-aligned the mech, or it may have moved slightly if not fitted on tight enough. Check the mech's cage is parallel to the chain rings, and the outer cage plate about 3mm above the big ring.

 

[Tynan]

yes adjust but this is crossover surely?

why be in the small chainring and the smallesy cog?

 

[gwhite]

You don't say which plate on the FD the chain is rubbing. I would imagine it will be the outer if you are on the small sprockets and in this case the tension needs to be upped moving the FD outwards. Is this a double or a treble? If noting has moved the answer has to be the cable stretching I would think.

 

[Alf]

Was working fine until last week when I noticed that when I move over to the smallest 4 sprockets and I'm on the inner chainring, the chain rubs on the derailleur. Why? It's driving me mad as I can't fathom out why. I've loosened off the cable tension and gone right through the adjustment screws but to no avail. Why oh why am I being tormented like this?

Seriously, anyone got any ideas?

Sounds like something has moved. I would do as Fossyant says, then put the chain on the inside ring, loosen the cable right off, use the limit adjuster to get the derailleur to the right position (there will probably be some unavoidable chain rub when on the smallest couple of cogs, which you would not normally use anyway on the inside chainring), then tighten the cable until it just takes up all the slack. You might have to play about a bit with the cable tensioner after but not much. The trick is to get the limit screw set to the right place for the inside ring.

Sorry if this is just teaching you to such eggs - but it certainly should just be a matter of adjustment - starting, as Fossyant says, with making sure the derailleur outside plate is about 3mm above the big chainring and parallel to it.

Alf