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  1. #1
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    Front derailer help

    It seems like every time I ride my bike it shows another problem the previous owner neglected. So on my ride yesterday the front derailer started to act up. Here is what it is doing, it will shift down from the big ring to the middle ring no problem but it will not go from middle ring to small ring with any sort of pedaling power being applied. If I only pedal just enough to turn the cranks it will shift but when going up a hill and I want to drop down one more ring it won't go, the derailer will move and rub the chain but it won't drop it to the next ring. The derailer will shift up through all the rings just fine and just cruising the street to the store it works fine. Is my front derailer out of adjustment or is it worn out and done? I haven't ran into this problem with any of my past mountain bikes so I don't know where to start to try and fix this issue.

  2. #2
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    try backing off the L Screw

    It could possibly as simple as backing off the L (low limit) screw, or you may have a gummed up Cable/housing. If you pull the derailer further down manually does it move, or does it bottom out on the limit screw. It sounds like it is not dropping down far enough, hopefully it is just a small adjustment.
    Hope this helps.

  3. #3
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    Odds are that that's just the way it is, and you might be better off for it.

    Down shifting the Ft-derailleur is accomplished by the return spring. The shifter has to force the chain to lift up and over the teeth to intiate the shift. When there's lots of chain tension the spring doesn't have enough muscle to overcome the chains tendency to stay engaged on the cog it's on, especially if that cog doesn't have a gate (cut down teeth) to help.

    Another possibility is the the Ft-der. is too far forward and bearing on the chain where it's already beginning to engage the chainring. This is a common problem with certain frame geometries, and cannot be fixed.

    As I said, you might be better off adapting to the shift characteristics as they are. Shifts to the granny under load all too often result in the chain pinging past the granny and falling onto the BB shell.

    Learn to ease off the pedal pressure a bit for a smooth reliable shift.

    As TahoeBoy said, a bit of adjustment of the inner limit might also help, but it isn't a substitute for better pedalling and shifting technique.
    fb
    www.chain-L.com

    The key to solving any problem is to understand and address the underlying cause.

  4. #4
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    I'll try giving it a good cleaning tonight and checking the lower limit screw. As far as easing up when I shift, I've tried that with no luck, there has to be pretty much zero force on the chain for it to go down. I've had 4 other mountain bikes in the past with everything from base shimano derailers up to new XT derailers and have not had this problem before so I don't think its my technique. I'll clean it and tweak it tonight and see how it does on my ride tomorrow. I'll be riding the same trails tomorrow that I usually ride so in the spots it would act up before I'll know if I got it fixed.

    Thanks for the tips. If it still acts up after tomorrow and the mounting point looks ok should I look into replacing it?

  5. #5
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    Front shifters are pretty simple things. If it isn't a matter of a simple cleaning or the issue of position, don't scrap it until you've seen how it performs without a cable. Shift up and down by pushing directly on the actuating arm.

    If that works well manually, but still not as well with the cable, it's a cable problem. Either the cable is packed with goo (highly technical term) from wet riding, or there's a kink or pinch somewhere. Strip the cables and housings clean & lube and try again.
    fb
    www.chain-L.com

    The key to solving any problem is to understand and address the underlying cause.

  6. #6
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    Ok, so I cleaned the derailleur and lubed the pivots and adjusted the lower stop and it still acts the same. The guy I rode with yesterday said the derailleur itself looks like it is a little bit too high above the chain rings so I'm going to bring it down where he said it should be and see what happens. I also put new chain rings on my bike before this last ride since the old ones were worn and one had a missing tooth but it didn't make any difference in how the bike shifted. If anyone else has any ideas they would be of great help.

  7. #7
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    A riding buddy was kind enough to send me some links from the Park Tool website and it looks like my chain is at least a link or two too long. I'm going to pick up a chain tool after work and fix that and see what happens.

  8. #8
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    Quote Originally Posted by bmwjnky
    A riding buddy was kind enough to send me some links from the Park Tool website and it looks like my chain is at least a link or two too long. I'm going to pick up a chain tool after work and fix that and see what happens.
    Don't cut the chain hoping for any improvement in FD performance. Chain length has absolutely no effect on the front derailleur. Regardless of overall chain length the upper chord where the FD operates is always the same length running in a straight line from the top of the cassette to the top of the chainrings.

    Before you decide to cut the chain, make sure it has a reusable clip link, otherwise you'll have to replace the special Shimano closure pin.
    fb
    www.chain-L.com

    The key to solving any problem is to understand and address the underlying cause.

  9. #9
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    when you do get it in the small chainring, does the derailleur rub the chain?

  10. #10
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    Quote Originally Posted by FBinNY
    Don't cut the chain hoping for any improvement in FD performance. Chain length has absolutely no effect on the front derailleur. Regardless of overall chain length the upper chord where the FD operates is always the same length running in a straight line from the top of the cassette to the top of the chainrings.

    Before you decide to cut the chain, make sure it has a reusable clip link, otherwise you'll have to replace the special Shimano closure pin.
    Ok, so should I still adjust its height above the rings then?

  11. #11
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    Quote Originally Posted by golfernut78
    when you do get it in the small chainring, does the derailleur rub the chain?
    Only if I cross chain it down to the smallest cog, but I know that isn't good for the chain so I don't do that unless I have to.

  12. #12
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    I'm goin to say to watch some you tube videos and attempt to re adjust the entire thing. if you have some decent mechanical comprehension you should be able to get a good under standing of the system and get it operating. if that fails take it to a bike shop. the adjust should cost about 10 bux.

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