Chain rubbing on front derailer?

[soulful dog]

My brother has just bought a 2nd hand bike and has noticed the chain is rubbing against the front derailer, which it is doing all the time. How much of a problem is this, and is it easily fixed?

 

[HLaB]

Most likely the cage will be a wee bit off, its not a hard thing to fix; an allen key is all you really need. Bike tutor might shed light on the subject.

 

[soulful dog]

Ta much, "not a hard thing to fix" will be just what he wants to hear

 

[Norm]

It might be even easier than that, depending on the bike and the mech, it might just be that he needs half a push on the shift lever to move the mech across without changing to another ring. My old MTB needs a tweak on the thumb shifter if I move more than a couple of gears at the back.

It might also be that he's riding with the chain crossed over too far, if he is using the big rings front and back, or the little rings front and back, the chain run won't be straight and he'll be pedalling harder than needed just to wear the chain.

 

[peelywally]

It might be even easier than that, depending on the bike and the mech, it might just be that he needs half a push on the shift lever to move the mech across without changing to another ring. My old MTB needs a tweak on the thumb shifter if I move more than a couple of gears at the back.

It might also be that he's riding with the chain crossed over too far, if he is using the big rings front and back, or the little rings front and back, the chain run won't be straight and he'll be pedalling harder than needed just to wear the chain.

old shimano gears had a name for that dammed if i can remember it though ,


good call .

tension something ?

 

[iAmiAdam]

If it's a road bike, it probably has a trim feature, that might not be set up properly. But it's probably not the trim.

 

[zacklaws]

It may also be down to not being adjusted properly, there should be two screws which adjust the movement of the cage on the mech, outwards and inwards, I have a feeling the distance to clear the chain is 2mm, but I may be wrong. If the mech is Shimano, just get the part number and go onto the Shimano website and search for the part number and there should be a manual on how to set up and adjust the mech.

I've been up for 48 hours and I'm a bit cream crackerd so I cannot be any more specific, my heads spinning.

 

[soulful dog]

The bike is a Carrera Subway 2 (not sure how old but it's only got 16 or 18 gears compared to the 24 speed current model), and he says there's no problem changing gears but it's rubbing immaterial of what gear he's in.

 

[PpPete]

Certainly don't want to mess with the H & L screws on the mech, they only change the outer limits of travel of the mech..... chances are it's the cable stretched a fraction.

Does the "cage" of the derailleur mec seem too far to the left, so the chain is rubbing on the right hand side?
If so, turn the cable adjuster anti-clockwise, half a turn at a time, until chain is stops rubbing.

 

[Rob3rt]

I had this issue a few weeks ago, followed advice from PpPete, it was just the cable had stretched over time, a bit of tensioning and it was running nice and smooth within minutes. Try that before you get your tools out.

 

[Angelfishsolo]

Certainly don't want to mess with the H & L screws on the mech, they only change the outer limits of travel of the mech..... chances are it's the cable stretched a fraction.

Does the "cage" of the derailleur mec seem too far to the left, so the chain is rubbing on the right hand side?
If so, turn the cable adjuster anti-clockwise, half a turn at a time, until chain is stops rubbing.

+1

 

[zacklaws]

Certainly don't want to mess with the H & L screws on the mech, they only change the outer limits of travel of the mech..... chances are it's the cable stretched a fraction.

Does the "cage" of the derailleur mec seem too far to the left, so the chain is rubbing on the right hand side?
If so, turn the cable adjuster anti-clockwise, half a turn at a time, until chain is stops rubbing.

And what happens if the outer limits of the travel of the mech is incorrect to start with, maybe set up incorrectly by Halfords or maybe the previous owner has tinkered with it, then no amount of turning the cable adjuster will increase the limit of travel to clear the chain.

I also did a search for that particular bike online and found someone else who had the same problem in a review of it, and they said that no matter what they did they could not cure the problem, but I myself cannot see why as it is a simple enough job to sort out, unless something is bent or broke.

Here are some reasons for it which I have extracted from another forum:-

1. Wrong chain size (8-speed chain in a 9-speed derailleur, that's what I have)
2. Derailleur clamp set too low or too high on seat tube
3. Wrong cable tension
4. Wrong derailleur angle
5. Wrong gear combination
6. Wrong limit screw setting

And from the Park tools website:

http://www.parktool.com/blog/repair-help/front-derailleur-adjustments

 

[Rob3rt]

And what happens if the outer limits of the travel of the mech is incorrect to start with, maybe set up incorrectly by Halfords or maybe the previous owner has tinkered with it, then no amount of turning the cable adjuster will increase the limit of travel to clear the chain.

I also did a search for that particular bike online and found someone else who had the same problem in a review of it, and they said that no matter what they did they could not cure the problem, but I myself cannot see why as it is a simple enough job to sort out, unless something is bent or broke.

Here are some reasons for it which I have extracted from another forum:-

1. Wrong chain size (8-speed chain in a 9-speed derailleur, that's what I have)
2. Derailleur clamp set too low or too high on seat tube
3. Wrong cable tension
4. Wrong derailleur angle
5. Wrong gear combination
6. Wrong limit screw setting

And from the Park tools website:

http://www.parktool....eur-adjustments

Then it wont move as you increase the cable tension and you will then realise that the problem wasnt cable tension, one potential problem eliminated?

 

[zacklaws]

Then it wont move as you increase the cable tension and you will then realise that the problem wasnt cable tension, one potential problem eliminated?

So then you have to go back to possibly having to adjust the H&L screws, but its already been mentioned not to mess with them, or perhaps the posting should have been more detailed what procedures to actually do and not what to do.

The simple solution is if the chain is rubbing on the outside of the chain, try and move the cage physically outwards with your hand, if it does not move, the H limiter needs adjusting to allow more travel of the cage outwards to get clearance along with tightening up the cable by the screw adjuster to facilitate the extra movement, If the cage does move outwards but moves back to touching the chain, then the cable just needs tightening. If the cage is rubbing on the inside of the chain, whilst on the outer ring, then the cable needs slackening. This is all providing that the mech is set up correctly on the frame and has also not been damaged