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  1. #1
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    Trek 7700 front derailleur problems

    Hi! I just purchased a Trek 7700 and am having significant shifting problems. I'm fairly new to bicycle riding and the language, so forgive me if I can't explain things just right.

    When I first rode the bike the chain would chatter against the front derailleur in the low gears(at high speeds). The shop fixed this, but now the chain chatters in high gears(at slow speeds), unless I shift it just right. I can't use all 9(or even 6) rear gears with any of the 3 crank sprockets. I think the bicycle shifts very well, but the chain hits the front derailleur in many positions. The chain fell of the crank(to the inside) earlier today.

    I've looked at reviews of this bike and found a few posts that state exactly my problem:

    "Weaknesses:
    The Shimano DEORE XT rear detailleur unquestionably delivers positive shifting, there are significant problems with the front derailleur that would make you think twice about buying a Trek 7700 -- the chain on the middle front sprocket and either of the two outside rear sprockets will result in noisy chain chatter. Additionally, the chain on the front outside sprocket and either of the two inside rear sprockets will create noise."

    and

    "Weaknesses:
    rear gears are very sloppy and hard to adjust. Even the dealer had a hard time adjusting the rear derailer. It is fixed by changing to a road racing, more solid, gears."

    What needs to be done to fix this? Am I doing something wrong? I love the bike, but this shifting really worries me. They told me at the shop that the shifting was normal and I was "cross chaining."
    Any comments would be great. Thanks!
    -Andrew

  2. #2
    Chi
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    Can you list some of the combinations of gears you are using?

    Like, list your front and rear gear combos:

    Big ring: 9,8,7,6,5
    Middle ring: 8,7,6,5,4,3,2
    Small ring: 5,4,3,2,1

    just an example. What's your combination?

  3. #3
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    Big ring: 9,8,7,6,5 (4,3,2,1 chatter)
    Middle ring: 9,8,7,6,5 (4,3,2,1 chatter)
    Small ring: 9,8,7,6,5,4 (3,2,1 chatter)

    3,2,1 always chatter
    9,8,7,6,5 never chatter

  4. #4
    Chi
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    Two options for you:

    1. Take that data with you to your LBS and see if they will help you out. It's possible that last time you went, you may not have had enough information for them.

    2. Try to fix it yourself, which is fairly challenging, but achievable. Read Barnett's Manual on Front Derailleurs, Chs 30, 31, and 33, and then try to adjust the rubbing yourself. Amazingly enough, sometimes adjusting the height of the derailleur will sometimes solve chattering problems.

    When I installed my new XTR FD about two weeks ago, I spent 2 hours messing with the thing, but ultimately looked at my gf's bike to see how her FD was oriented in relation to the chain. Adjusted the height a little higher. This fixed most of my rubbing problems, but since the derailleur is a 9-speed, and I'm still running an 8-speed system, it still rubs. I expect the rubbing to go away after I get a full 9-speed system.

  5. #5
    Mel
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    I'm a new owner of a 7700, less than 100 miles so far. I haven't seen this problem at all, but I may have a pretty good excuse:

    I thought that the original gearing was a little too wide. I couldn't see a real need for anything less than about 30 gear-inches (I don't climb walls) or more than about 100 gear-inches (I think I'll just coast down cliffs ) so I had the dealer replace the original cassette with a 13-23. That's 13, 14, 15, 16, 17, 18, 19, 21, 23. This combination goes from about 33 to 100 gear-inches with lots of relatively small steps in between and only a couple of essentially duplicated gears. I love it!

    Mel

  6. #6
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    I have been riding a trek 7700FX for a year and three months now. Chatter on the low rear derailleur gears seems to develop as soon as a month of so after tune ups. I can get rid of it by tightening and loosening appropriate screws, but it seems to redevelop in a manner that seems to mockl my efforts. I think it is design flaw.

  7. #7
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    shifting cables stretch just like brake cables, and when they stretch, sometimes the chain will rub.

    the chain chatter the original poster is experiencing is due to improper adjustment of the front derailleur. i believe it's the "low" limit screw that could use at least a quarter turn out. that should get rid of the chain noise. bare in mind that when you loosen the limit screw, you'll also have to re-adjust the cable tension.

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