# Chain Rubbing on front derailleur



## Truth (19 Mar 2015)

Hi all,
Help , I am confused !
The chain is rubbing on the front dérailleur but only when in the smallest rear cog and when on the two largest front ones, if that makes sense.
I have tried adjusting the screws on the dérailleur , after watching how to adjust you tube videos , and frankly NEITHER screw seems to do anything at all. . . . . . . . 
Any ideas?
Also will the rubbing damage the dérailleur and/or chain ?
Cheers


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## gbb (19 Mar 2015)

Avoid using small rear - large front or vice versa, it will cause excessive wear on the components, They simply can't cope with those combos, no-ones can.
Look from above when in those combos and you'll see the chain 'bending' ..its bad for it.


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## Usehernamegood (19 Mar 2015)

I was once told by a local bike mechanic that if you ride with the chain on the largest cog - you're doing it wrong.


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## mrbikerboy73 (19 Mar 2015)

Large front and small rear cogs are fine. It's small front/small rear or large front/large rear combinations that you want to avoid. 
Sounds like a little more tension on the cable is needed to move the front mech out wards. If this doesn't work then it's the limit screw that needs a tweak.


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## Truth (19 Mar 2015)

I spend half the time in the saddle in large front small rear so I hope you are right Mrbikerboy!
How do I change the tension on the cable please
Sorry , I haven't got a clue and as I say adjusting the 2 small derailleur screws did nothing at all for some reason?
Thanks for all of the replies


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## Bazzer (19 Mar 2015)

The screws should make an adjustment. On my old bike I wasn't convinced the screws were working until I screwed them IIRC anti clockwise, then found the mechanism wouldn't move, so I knew they were working.. So having found a way to stop the gear changing, I knew the opposite way would stop the rubbing.
I presume from your comment about the two biggest rings at the front, that you have a triple front. The gear change gate can be adjusted to stop rubbing when on the middle ring by the barrel adjusters on the gear cable. These will be fitting on the outside of the gear cable with a screw thread, which may or may not be visible. This might be just above the front mech or further up the frame where the cable outer stops at a lug. Alternatively if the front mech is a Shimano, and the levers are STI, the barrel adjuster mat be near the lever. Also I think there is a halfway movement of the gear/brake lever which can stop the rubbing, provided the cable tension isn't too loose.
I know you say you have looked at you tube videos, but in my experience the quality varies, even though they are telling you the same thing. Have look at at as many vids as you can find for a triple front (assuming that is what you have). If you have still having problems, or if your front mech doesn't accord with with what you are seeing in the vids, for example not having barrel adjusters, it could be visit to your LBS.


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## si_c (19 Mar 2015)

As @Bazzer says, with the derailleur there is often a barrel adjuster in the cable line somewhere on a road bike you can adjust to increase the cable tension which will push the deraiileur outwards slightly and hopefully stop the rubbing effect. If it doesn't you may need to adjust the limit screws (the one labelled H or high) to allow it to push out a bit more.

If you are on a mountain bike then there may well be a barrel adjusted on the shifter similar to the ones on your brakes. If not then take it to the LBS should take them a matter of moments to fix, but make sure they show you what they did so you know what to do next time.


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## Nigelnaturist (19 Mar 2015)

As @Bazzer says, somewhere along the gear cable there is a barrel adjuster, depending on the shifters, Tiagra/Sora/Claris can have one as the gear cable leaves the shifter, 105 and above its likely to be either inline somewhere or on the down tube where the down tube shifter would be, turn clockwise to tension, the screws on the mechs themselves are just stop adjusters, in other words stop the shifter moving to far so as the chain comes off, once set they very rarely need adjusting. If you hold the cage in one hand and adjust the screw you will feel the cage move, however only do it when on the large or small rings, with the shifter set to that position, and adjusting the appropriate screw, if nothing happens its likely to be the wrong screw. There is also a trim feature, where by you can press the lever in a little and will move the cage to the right, press the release paddle/thumb lever a little and moves slightly to the left, this is only on the front.


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## Truth (19 Mar 2015)

Thanks everyone 
I should have said in the first place that I have got a Kona Dew Hybrid, its a triple change. The derailleur is Shimano, think the trigger gears are too
So there should be a barrel adjuster by the trigger then, similar to my brake ones? I think I have noticed that in fairness. I take it I adjust the left hand one that changes the triple front?
I don't understand how the two screws on the derailleur did nothing, no harm , no good? Weird.
Will the rubbing do any damage?


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## Bazzer (19 Mar 2015)

Damage? Well you have metal rubbing on metal that isn't supposed to except temporarily as you change gear.Why create a problem if it's fixable? Short term though I would say no, though it is also going to depend on your mileage in that term.
Personally that noise annoys the snot out of me, so when it happens, I will gradually get more cross and as a result damage something.


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## derrick (19 Mar 2015)

Not all bikes come with barrel adjusters, http://www.ebay.co.uk/itm/141485627507?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
But they are really handy to have on the front derailleur, or you could just retention the cable.


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## Truth (19 Mar 2015)

Bazzer said:


> Damage? Well you have metal rubbing on metal that isn't supposed to except temporarily as you change gear.Why create a problem if it's fixable? Short term though I would say no, though it is also going to depend on your mileage in that term.
> Personally that noise annoys the snot out of me, so when it happens, I will gradually get more cross and as a result damage something.



Just gone into a dimly lit shed and turned the adjuster on the left hand trigger anti clockwise a quarter. SEEMS to have done the trick, when turning pedals backwards now I can't hear any scraping, although I will only know for sure tomorrow when I ride it!
Just hope me adjusting the derailleur screws won't cause any problems in the near future
Once again thanks for everyones time and advice


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## si_c (20 Mar 2015)

Truth said:


> Just gone into a dimly lit shed and turned the adjuster on the left hand trigger anti clockwise a quarter. SEEMS to have done the trick, when turning pedals backwards now I can't hear any scraping, although I will only know for sure tomorrow when I ride it!
> Just hope me adjusting the derailleur screws won't cause any problems in the near future
> Once again thanks for everyones time and advice



Always feels good to fix things yourself 

The screws on the derailleur are the limit screws, basically they are what stops you accidentally shifting the chain over the top and bottom of the chainrings at the front. If you were having a rubbing derailleur at the front it is likely that you won't have any problems with it there. The two screws are labelled L and H for low and high. If the chain drops off the cog when shifting onto the smallest gear then you need to adjust the screw labelled L and if you do it right you should see the deraiileur move almost imperceptibly away from the frame of the bike, and that should fix the problem.

If of course you have a problem with the chain falling off and wrapping around your crankarms and pedal you need to adjust the H screw. Here's a good explanation for adjusting the front derailleur.


View: https://www.youtube.com/watch?v=tfBiXgf8JxI


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## Truth (20 Mar 2015)

Thanks si_c ! I feel good about it until 7.50 when I ride it and realise I have buggared the gear settings up! 
I will post later with an "idiots update" 
Have a good day all


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## Bazzer (20 Mar 2015)

A quarter turn shouldn't have made that much difference other than to the rubbing, so it sounds as if those screws did actually work.


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## Truth (20 Mar 2015)

Not sure whats happened Bazzer , yesterday evening the chain was rubbing and then last night , when I tweaked it a quarter , it stopped .........
Anyway the journey in was great and no problem , lets hope it stays like that
Have a good weekend everyone !


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## Truth (27 Mar 2015)

damn , damn , damn ! Its started rubbing slightly again. Adjusted the "barrel" on the handlebar trigger gears and its made no difference and the little dérailleur screws made no difference either , I just can't understand it really???
May have another look in the morning but only really affects one gear now really


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## Truth (27 Mar 2015)

mrbikerboy73 said:


> Large front and small rear cogs are fine. It's small front/small rear or large front/large rear combinations that you want to avoid.
> Sounds like a little more tension on the cable is needed to move the front mech out wards. If this doesn't work then it's the limit screw that needs a tweak.



Next question , as I can't see a barrel adjuster (other than the one right on the trigger lever which is doing nothing) on the cable , how do I increase the tension to move the derailleur out ?
Sorry. Again if this is all very basic stuff to most !


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## Bazzer (28 Mar 2015)

Assuming the rubbing has come back on the middle ring of the chainset, if you are sure the adjuster near the trigger isn't doing anything, have a look along the cable all the way to the front mech. If there is no other adjustment capability, I think you have two choices. Firstly buy a barrel adjuster and fit it to the outer cable. See @derrick post earlier. Or loosen the cable near the front mech and using all three hands  move the mech sufficiently across to stop it rubbing, hold the cable tightly with pliers to stop it slipping and then tighten the locknut with an Allen key/spanner.


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## Nigelnaturist (28 Mar 2015)

To adjust an FD from scratch,

1 ensure your left lever is in the low postion,
2 disconnect the cable at the pinch bolt on the FD,
3 make sure the FD cage is parallel with the rings,
4 adjust the low stop screw so the cage is about a 0.5-1mm from the inner ring/chain,
5 reattach the cable pulling taught with pliers try not to damage the cable, this should take up the slack you would normally take up with the barrel adjuster,
6 once done shift up through the big rings, if its doesn't move onto the outer front ring the high stop needs to be undone slightly.

Tip if when the cable is detached hold the cage with one hand and the adjust with the other the movement will be felt easier than looking for it visually, once you know which screw is the low stop you will know the other is the high stop, also if nothing happens chances are its the high stop you are adjusting, so adjust the other, then reattach ect..


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## Nigelnaturist (28 Mar 2015)

Images of barrel adjuster postions


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## Truth (28 Mar 2015)

Thanks Bazzer and Nigel! The rubbing is worst when in the middle front (2) ring and the largest (7) back cog. Also rubs a tiny bit in the largest front and largest back.
I will have a look later, just worried about buggaring it up and not being able to use it!


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## Nigelnaturist (28 Mar 2015)

@Truth need to clarify, middle front (2), largest rear cog, is usually 1 which is the low gear, biggest gear smallest rear cog is usually the higher number 6,7,8,ect. 

You shouldn't really use the the large front chain ring and largest rear cog (1) this is known as cross chaining, and will lead to unnecessary chain/cog wear due the more extreme angle of the chain, and because of the more extreme angle chain rub on the FD cage is more than likely, however if it is the large front and large gear i.e. small cog, than the FD is not moving far enough and the Hi-stop screw needs slacken off a touch or a little bit more tension on the cable, which from what you describe is likely, 
if its rubbing on you middle front chain ring and your rear smallest cog (biggest gear, 7) your FD cage needs to move slightly towards the large chain ring, adjusting your hi low stop screws will have no effect, all these do is stop the cage from moving to far so that the chain doesn't come off, so you need to adjust the cable tension, as I described. If you follow what I wrote before, you can't go wrong.


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## Truth (28 Mar 2015)

What I meant to say was middle and big front and smallest back was when there was rub, I am bloody hopeless, feel like I am wasting peoples time sometimes! SORRY
Anyway its sorted!
Did some fiddling about.
Loosened off the barrel adjuster by the trigger first
I actually adjusted the back gears then by loosening the screw and then (i know you said not to Nigel BUT it seemed to help) adjusted the front derailleur screws. I saw for the first time that there is very slight movement there.
Can I add at this point that a bike frame would have been priceless while doing this, luckily my neighbour helped me as he saw me riding up and down the road aimlessly and asked what was wrong!
He knows a thing or two about bikes and gave me a few pointers as well as you guys  . He also held the bike with me while I went up and down the gears making adjustments.
Anyway , I now have a clean bike, clean chain, clean cogs, clean everything in fact BUT best of all a rub free ride!
Thanks again all and I will leave you in peace now until my next daft question arises at some point in the future .
Have a good weekend.


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## Bazzer (28 Mar 2015)

Glad it's sorted.
(Until the next time )


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## Nigelnaturist (28 Mar 2015)

@Truth anytime, glad its working right.


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## mrbikerboy73 (28 Mar 2015)

@Truth those guys beat me too it and gave far more complex and informative instructions than I could have done! 
Glad you've got to sorted out


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## Truth (28 Mar 2015)

Cheers, genuinely really appreciate all the help with this and other previous daft questions 
Sometimes I don't think you lot know how useful and helpful you are


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## Nigelnaturist (28 Mar 2015)

Truth said:


> Cheers, genuinely really appreciate all the help with this and other previous daft questions
> Sometimes I don't think you lot know how useful and helpful you are


One day you will be doing the same.


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## Truth (28 Mar 2015)

I VERY much doubt that mate !


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## Nigelnaturist (29 Mar 2015)

Truth said:


> I VERY much doubt that mate !


Just remember bikes aren't rocket science, and they all pretty much work the same.


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