Front dérailleur (again)

[BrynCP]

I am having problems with my front derailleur again. It's an Altus one on a Giant Escape 2.

I have cleaned and lubricated it, which seems to have got it moving again, as it got stuck mid ride today on the large chain ring and wouldn't come off - shifting from 3 to 2 there was no movement of the derailleur, same from 2 to 1 (on the shifter, the chain was still on 3) although the shifter seemed to stop between the two.

Nothing is bent, it all looks fine. When I try to go from 2 to 1 the derailleur cage moves a little bit and just rests on the chain, which isn't far enough to move the chain off. There is no tension in the cable when in the 1 position. Changing the "Low" screw has absolutely zero effect no matter what I do with it, it seems entirely redundant, it's definitely the low screw as it's labelled. I can't move the derailleur with my hand either, it's like it's at it's absolute inwards it can go.

Anybody any ideas?

 

[jack smith]

make sure you undo the cable before adjusting the screw, make sure the shifter is all the way down, pull the cable really tight with pliers and tighten the bolt, that sorted the exact same issue with my sora front mech, is it inline with the chainring?

 

[BrynCP]

It's probably obvious I don't understand this stuff well, but I am not sure what you mean by is it inline?

Also, surely if there is no tension that should mean it would shift down to the small ring as I thought that was the default position for it to spring back to?

 

[jack smith]

When you look down from the top does the cage of the mech line up with the chain ring? If not it could be preventing it pushing the chain back down into the small ring

 

[I like Skol]

Is the mech too low? It could be binding on the tips of the chainring if it has slipped down the seat tube. If your bike has traditional cable routing under the bottom bracket the cable will be trying to pull the mech towards the bottom bracket if the clamp isn't tight enough. There should be a few millimetres (I think Shimano normally specify 3-4mm) of daylight between mech cage and the tips of the teeth.

 

[BrynCP]

Thanks all. However, it has just started working all of its own accord? It hasn't worked for weeks, if not months. I flushed it out with GT85 on Tuesday, and then lubricated and wiped. The ride last night still didn't work. Tonight I pulled it just to see and it moved much further back and very easily shoves the chain onto the small chain ring.

No idea what has caused that, either the lubrication took a long way to work through, or something got dislodged?

Have to adjust the screws again now as unfortunately it's throwing the chain off the large ring.

 

[gwhite]

Thanks all. However, it has just started working all of its own accord? It hasn't worked for weeks, if not months. I flushed it out with GT85 on Tuesday, and then lubricated and wiped. The ride last night still didn't work. Tonight I pulled it just to see and it moved much further back and very easily shoves the chain onto the small chain ring.

No idea what has caused that, either the lubrication took a long way to work through, or something got dislodged?

Have to adjust the screws again now as unfortunately it's throwing the chain off the large ring.

It sounds as if the winter crud has jammed up the mechanism. Lube the FD again but this time put the FD in the smallest chain-ring. Now grasp the FD operating cable at the Down tube and pull as if a bow string while operating the pedals. Do this until you are certain the FD is entirely free-moving over all of its arc.

 

[BrynCP]

Thanks.

Re lubricated as above, adjusted the screws (which actually still seem to have little to zero effect) and adjusted the barrel adjuster and I now have full, smooth movement and access to all the chainrings which is good for my knees!

 

[KneesUp]

I have just got hold of an old bike with an Altus on it (it won't be the same as yours - bike is c.20 years old) and it won't move either. Having removed it and investigated, I think the aluminium of the cage has fused with the steel pin that it moves around because of the damp. I don't know if there is much I can do about it, which is a shame because otherwise the mech looks hardly used. Could the same thing be happening to yours?