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  1. #1
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    i-drive chain slip

    Hello,

    I've been having some problems with my chain slipping from my rear cassette under heavy load, and think it may be related to an i-drive maintenance issue. Hopefully one of you i-drive experts out there can provide some help for me- the LBS hasn't been too much help on this one.

    I have this bike: BikePedia - 2004 GT I-Drive 1.0 Complete Bicycle and have been experiencing an annoying chain slip on the rear cassette when apply a really strong pedal stroke in certain gears (like if I am trying to "power over" something- so not related to shifting). I've had the bike for a while, but was not an issue in the past. I have replaced the cassette (sram mid-level 9sp), chain(sram mid-level 9-sp), crank (race face- mid level), derailleur (lx m580), hanger, and cables/housing and this problem still persists. I think I have the bike pretty well dialed in, so I don't believe it's slipping due to the derailleur being out of line, especially as I've adjusted it slightly off from perfect to make sure that isn't the issue. At this point, I have narrowed it down to the following in my own mind, but I'm not a bike mechanic, so I could be missing something obvious.

    1. Perhaps something to do with the "b-tension" screw on the derailleur- when following the tuning instructions, it isn't clear to me where this should be set.

    2. Perhaps my chain is too slack? I followed the instructions for the derailleur (on both large sprockets- add 2 links).

    3. Lastly, I was thinking it may have something to do with my i-drive. There is quite a bit of play rotationally (0.5 cm or so) when I jiggle the eccentric body (the aluminum thing just inside the frame on the non-crank side). I can't remember if it was like this when new. Is this typical, or a sign that it needs maintenance, and if so, is it likely that this may be the cause of my chain slip issue?

    If anyone has any idea what is going on with my bike, I'd really appreciate it. It's hard to reproduce, as it only happens in certain gears, and in cases of extreme load (not while shifting though), but still, it didn't used to happen, and is extremely annoying when it does.

    Thanks in advance for any wisdom you can provide!

  2. #2
    Huckin' trails
    Reputation: David C's Avatar
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    2 things I can answer so far :

    Your b-screw should be as slack as possible without compromising any shifting. Slack means to screw it in less as possible, to get the upper pulley as close as possible to the cassette's biggest cog, but that won't stuck the chain when shifting to the bigger cog. A b-screw that is screwed in too much put the upper pulley to far behind the cassette and can cause the problem you are describing.

    See my b-screw here :

    Good
    i-drive chain slip-imageuploadedbytapatalk1342399801.362627.jpg

    Not good
    i-drive chain slip-imageuploadedbytapatalk1342399933.182339.jpg



    Then for your i-drive being loose, that's not normal. You'll need to tighten it back, but since it's been a while that you rode it loose, I'd recommend to service it because you might have damaged the bearings and bearing races. There is a thread in the GT forum about the procedure. You can do it yourself, only need 2 tools. The correct tool to remove your BB and a spanner tool like the Park green BB spanner tool. I don't think this would affect your chain issue however.
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  3. #3
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    Thanks so much, David!

    The b-tension thing seems like an obvious fix- not sure why I didn't catch on to that myself, but thanks a bunch. It is actually much closer to being fully slack, but I do have some thread left, so hopefully by backing it out it will solve the issue. I'll take a look at the eccentric too- found a couple good threads on that.

  4. #4
    Huckin' trails
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    Let me know how it work out with the b-screw.


    Here's a pic of my non-drive side i-drive :

    i-drive chain slip-imageuploadedbytapatalk1342489084.795553.jpg

    i-drive chain slip-imageuploadedbytapatalk1342489122.301064.jpg
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

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