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  1. #1
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    How do you know when to replace front deraileur?

    Hey guys,

    I recently accquired a 1999/2000 GT Karakoram, I have had it taken to the bike shop and had the filthy cassete cleaned up and also had the chain replaced. The rear deraileur seems to be working perfectly fine but after a few visits to the local bike shop I am still having problems shifting on the front deraileur. The chain seems to skip and sometimes altogther just wont go up or down on larger gears (1,2,3). The bike shop's as mentioned before have adjusted the front derailuer a couple of times and tell me that the problem should be resolved but no dice. When should the front deraileur be replaced and what are typical signs that its not working properly?

    Thanks guys!

  2. #2
    REALLY?
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    Usually deraileurs dont care about what posistion they are in, what I mean is, the mechanism or you could say brain of your deraileur is the shifter, there are like little teeth or gears similar to what you might find in the innerworksings of an old watch that are inside your shifter is the best way I can explain it and it could be those teeth in the shifter are worn out. You could try replacing the shifter and getting a new cable, because as long as the deraileur isnt bent or anything it should work fine.
    Last edited by jeffgothro; 11-26-2008 at 08:55 PM.
    DJ, "Because I'm sure the world need's more dudes stalking the woods stoned out of their mind carrying a deadly weapon."

  3. #3
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    Quote Originally Posted by jeffgothro
    Usually deraileurs dont care about what posistion they are in, what I mean is, the mechanism or you could say brain of your deraileur is the shifter, there are like little teeth or gears similar to what you might find in the innerworksings of an old watch that are inside your shifter is the best way I can explain it and it could be those teeth in the shifter are worn out. You could try replacing the shifter and getting a new cable, because as long as the deraileur isnt bent or anything it should work fine.

    Thanks for the response. That is the only thing I haven't bothered to tinker with although the bike shops sprayed it with some kind of lubricant. I'll take it in tomorrow and see what can be done in regards to that.


  4. #4
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    If the chain is skipping after you have shifted, your front chainrings could be worn.

    More than likely, the front derailleur is absolutely fine. Like jeffgothro was saying, the FD is just a guide on a spring, with no indexing of its own. The shifter tells it what to do.

    If you want, you could try working on the FD yourself, instead of taking it to the shop. It is a fairly straightforward procedure that just requires a bit of patience. Park Tool has a great repair directory; here is a direct link to FD adjustment.

  5. #5
    REALLY?
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    Quote Originally Posted by Call_me_Al
    If the chain is skipping after you have shifted, your front chainrings could be worn.

    More than likely, the front derailleur is absolutely fine. Like jeffgothro was saying, the FD is just a guide on a spring, with no indexing of its own. The shifter tells it what to do.

    If you want, you could try working on the FD yourself, instead of taking it to the shop. It is a fairly straightforward procedure that just requires a bit of patience. Park Tool has a great repair directory; here is a direct link to FD adjustment.

    ^^^^ that would be the cheaper easyer solution, try that first (why didnt I think of that duhhhh, I know better) and if its not the chainrings then go to the shifter, but try Call Me Al's solution before you try mine.
    Last edited by jeffgothro; 11-27-2008 at 11:06 AM.
    DJ, "Because I'm sure the world need's more dudes stalking the woods stoned out of their mind carrying a deadly weapon."

  6. #6
    Rod
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    Does the front derailleur move the chain between the cogs 1,2,3 and then the chain skips once it's on the cogs or does it just skip when trying to shift? I'm just trying to clarify the problem.
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  7. #7
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    If the chain is shifting off the chain ring on its own. I would expect you are hearing some sort of draging noise from the chain hitting the derailer guide. If you are hearing the noise I would check the cable tensio/adjustment at the shifter. Also make sure when you are shifting the shifter is hitting the indentment that locks the derailer into the gear.Shifter could be worn out and allowing the derailer to move back slightly. If your not hearing the chain hitting the derailer I would look for a bent sprocket/tooth.
    Adjusting the derailers is simple ounce you figure it out. I spent $100 of dallors at shops to get the bike home with a slightly better derailer adjutment. You just can't get it perfect on a bike rack. They do test ride them but pretty quickly.
    The screws on the derailers are only limiting screws to keep the chain from falling off the casset/cogs in either direction. The fine tuning is made at the shifter with the barrell adjuster. I think some shimano's have barrell adjusters at the derailer themselves. I ride up a slight incline while fine tunning my barrell adjusters. This puts a slight load on the entire system,frame,cranks,cogs,etc. good luck.

  8. #8
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    Hey guys,

    Thanks for all the information, sorry It's been a bit since I have logged in but been busy with Holidays etc. There seems to be alot of potential solutions, The shifters are Shimano and do have the barrell adjusters which I have tinkered with. The problem seems to have been resolved at the moment but I was thinking that the problem would lay with the shifters and or FD, I haven't had much time to get out and ride due to the 30 something degree weather lol. Thanks for the link Call_Me_Al, it's pretty damn handy!

  9. #9
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    The front derailleur is a pretty reliable item. I've never replaced one, period.

    As long as there is no surface rust and it moves freely when the cable is not attached, it should be good to go.

    However, front shifting problems are related to several things, including front derailleur position, and you cannot assume the original position was correct.

    It is actually one of the hardest problems to fix.

  10. #10
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    ^^Worst Advice Ever?^^^

    Quote Originally Posted by jeffgothro
    Usually deraileurs dont care about what posistion they are in, what I mean is, the mechanism or you could say brain of your deraileur is the shifter, there are like little teeth or gears similar to what you might find in the innerworksings of an old watch that are inside your shifter is the best way I can explain it and it could be those teeth in the shifter are worn out. You could try replacing the shifter and getting a new cable, because as long as the deraileur isnt bent or anything it should work fine.

    It's a front derailer. What's important about shifting with a front derailer are the shift ramps on the chain rings and not the internal components of the shifter.

  11. #11
    i also unicycle
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    sight unseen best guess: cable is stretched and housing is filthy. replace both. fairly cheap and easy to do, just make sure to match housing lengths. also make sure the derailluer is mounted straight. sometimes they can get bumped slightly making adjustment nearly impossible but i can't imagine a shop would've missed it.
    mtbr says you should know: i work in a bike shop.
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