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The front derailleur on my mountainbike sometimes gets stuck in high gears. When this happens and I want to shift down I can nudge it a bit with my foot and it will spring back to the lower gear.

I think the spring is still strong enough because just a small nudge is enough. I haven't been fiddling with the two adjuster screws, and -as I said- if I nudge the derailleur after shifting it jumps to the correct position. The issue seems to be the (admittedly pretty large) amount of gunk that has gotten stuck in the derailleur over the years. I tried applying some WD-40 to the moving parts but two small applications have not really helped remove the gunk. Is this still the way to go or is there a better way to get the gunk out without completely removing the derailleur (which I -for now- am too lazy to do).

This question deals with a similar problem, but it hasn't moved beyond the diagnosis part (which I have already done I think).

[update:]

I tried liberally applying WD-40 a few times over the course of a week, including some (aided by hand on the derailleur) shifting after each application. This mostly removed the issue when shifting from 3 to 2, but 2 to 1 remained. Today I went to my local car-cleaning station and applied a high-pressure hose to the derailleur. This removed all the visible gunk. I applied some oil, now shifting is as smooth as can be given the state of my chain and chainrings.

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It sounds like the cable or shifter may be sticking. When your problem occurs, stop and see if the cable is slack. If not, the problem is likely up-stream from the derailer. If the cable is slack, however, the shifter is sticking. –  Daniel R Hicks Sep 9 '13 at 0:06
    
It looks like a similar/repeated question to me.... –  hagubear Sep 9 '13 at 11:33
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Also, It is to do with your front derailleur clutch jamming....I had the same problem...it is most likely that... –  hagubear Sep 9 '13 at 11:34
    
Hi Daniel, the cable goes slack on the last stretch towards my front derailleur, so I think the problem isn't upstream. –  jilles de wit Sep 9 '13 at 12:35
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@hagubear , the question I linked seems to point in a pretty similar direction, but is stuck in the diagnostic fase (where I think I already know the answer but am unsure about how to proceed) –  jilles de wit Sep 9 '13 at 12:38
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3 Answers

up vote 5 down vote accepted

If you believe you have diagnosed the problem then a clean and a service should be all that is required. You don't have to remove the FD.

WD-40 will not displace mud effectively. I would:

  • use a hose with a decent amount of pressure to remove the gunk, wait for it to dry. (be careful not to spray around the bottom bracket)

  • apply WD-40 to any moving parts on the derailleur but focus on the pivot points to remove old lube.

  • once the WD-40 has evaporated apply some decent chain lube to the pivots.

If this doesn't fix the problem and the cable is moving freely the derailleur may be bent or the spring has lost the required tension.

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I've had this problem a few times an I agree with this for the most part. Except instead of a hose I've used small brushes (think tooth brush with very stiff bristles). I've tried both vinyl and brass bristles - what ever is handy. –  Arbalest Sep 9 '13 at 1:01
    
I'll try this this evening (with brushes, I have no hose available) and report on my progress. –  jilles de wit Sep 9 '13 at 12:36
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I think if you get most of the surface gunk off the WD-40 would be able to move any grit that is in the pivots. I live in an area that has a lot of dense heavy clay so cleaning out the FD usually involves holding the hose while it slowy erodes away at the clay!! –  DWGKNZ Sep 9 '13 at 19:18
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I would clean the derailleur but also replace the shifter cables and housing. In my experience, it is much more likely for the cables to be a little bit stuck than the actual derailleur itself.

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Hi Jan Van Besien, I see my cable go slack on the last stretch to my front derailleur when I shift down, so I think the cables are not stuck. –  jilles de wit Sep 9 '13 at 12:34
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I agree. If the cable goes slack something in the derailleur itself must be stuck. –  Jan Van Besien Sep 10 '13 at 9:45
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I had exactly the same problem last year due to running into snowy roads for a week or two. The front derailleur clutch jammed. DO the following:

  1. Put your gears to 1:1 position. This is the safest position to start with the optimum cable tension. Also, you will have less chances of messing things up.

  2. loosen the joint that is holding the derailleur cable for the front derailleur clutch. This is actually located near where your cassettes are (gear coggs).

  3. Clean the clutch joints and housings properly. If you have a thin-brissled brush, it is good. Otherwise, use a cleaning cloth.

  4. Clean as thoroughly as possible and make sure all the debris and small granules are not blocking any of the intersections/joints.

  5. Tighten the cable back in the joint, ideally and exactly where it was before.

  6. Check the up/down shifts for all the gear to ensure that you have got the correct tension level.

FUTURE REFERENCE: Depending on how heavy your ride schedule is, you should do it ideally every 4 months or so. In this way, you keep your bike in good condition as well as the safety. You don't want to be in the middle of the traffic and bashing your head wondering why your gear is not shifting down :p

I hope this helps.

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