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  1. #1
    meh....
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    Is middle ring/big cog cross chaining?

    I've got '04 XT cranks with the external bearings on a Truth and an XT 12-34 cassette. If I go middle ring and 1st, 2nd, or 3rd cog and try and climb the chain will try to jump down to the small ring unless I use the front der to hold it in place. There aren't any spacers between the bearing cup and bb shell face on the drive side, so I can't very easily move the whole shebang over.

    I haven't measured the chainline, I'll do that. And I don't know offhand the width of the bb shell, I'll measure that too. Maybe I'll end up putting spacers behind both rings and shove them over a bit, not sure what else I can do. I just switched from an 11-32 cassette and never had this problem, and I'm pretty sure I would have used those gears upon occasion.

    I don't have a big ring, just small, middle, and a bashguard.

    Monte

  2. #2
    1x9'er
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    Quote Originally Posted by Monte
    I've got '04 XT cranks with the external bearings on a Truth and an XT 12-34 cassette. If I go middle ring and 1st, 2nd, or 3rd cog and try and climb the chain will try to jump down to the small ring unless I use the front der to hold it in place. There aren't any spacers between the bearing cup and bb shell face on the drive side, so I can't very easily move the whole shebang over.

    I haven't measured the chainline, I'll do that. And I don't know offhand the width of the bb shell, I'll measure that too. Maybe I'll end up putting spacers behind both rings and shove them over a bit, not sure what else I can do. I just switched from an 11-32 cassette and never had this problem, and I'm pretty sure I would have used those gears upon occasion.

    I don't have a big ring, just small, middle, and a bashguard.

    Monte
    It could be called cross chaining, but I do it all the time with no problems on my bikes. One of my bikes is 1x9, meaning I only use the middle front ring, no front derailuer, and have a 9-speed cassette in the back. I use all 9 cogs with the middle ring with no problems. I set up the chain line so that the middle ring is in line with the middle (5th) cog. I use a bash ring on the outside of the cranks to keep the chain from jumping off to the outside and an N-Gear Jumpstop on the inside in place of the derailuer to keep it from jumping off to the inside. The Jump Stop is available at www.n-gear.com for 10 bucks, shipping included. There are other products as well that will do the same thing as the Jump Stop. To use any of them successfully though, you need a properly set up chain line and a properly working rear derailuer and shifter. Sounds like you have either chain line or derailuer/shifter adjustment issues, or maybe a worn out chain or cassette cogs.

  3. #3
    mechmann_mtb
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    it isn't necessarily the best chainline, but it isn't going to break anything. i ride 1X9 so i run through the whole cassette from the middle ring. it probably causes faster wear on the chain, chainring and cassette, but I like this setup. i have a couple hundred miles on this setup and no problems yet.

  4. #4
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    "Is middle ring/big cog cross chaining?"

    Good question and welcome to the 'chain jumps down' club. See link below..
    Chain jumps down a sprocket in front on bumpy downhills

    Could be that your parts are worn out. Give them a real close look over. I found a middle ring locally and will be installing that next to see if it solves my problem of the chain jumping down.

    Far as 'is it cross chaining'; I say no. That is my fav gear combo, middle frt and large rear. Main reason its my fav is cause of the trails I ride, lots of short steep hills and I need to go from a short high rpm pedal to tall low rpm pedal very quickly. So soon as I clear the hill in middle frt/large rear, I quickly punch the shifters and hit large frt/ middle'ish rear. If I drop down to the small frt on hills, it causes way too much time delay do to nearly 2x the shifting needed.

  5. #5
    meh....
    Reputation: Monte's Avatar
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    Thanks....

    I'll have to muck with it. Hope I don't have to use chainring spacers to get a better chainline.

    Monte

  6. #6
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    Maybe chainline but maybe your middle ring has issues such as one or more teeth out of centerline or it's not flat. Does the drop to the small ring happen at the same point on the middle ring?

  7. #7
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    I agree with the others....

    Not necessarily cross chaining... at least no worse than running granny and 3rd-4th cog which feels similar to me (I haven't run the numbers though).

    Let us know if you get it worked out because I'm about to upgrade my drive train and will probably go with this same set up.... XT hollowtech cranks and 12-34 cassette.

    My old XT cranks and 11-32 cassette work fine with this.

    I'll second the suggestion to check the middle ring. Could have a/some bent tooth/teeth.

  8. #8
    meh....
    Reputation: Monte's Avatar
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    Well the chainline is 47.5mm, as close as I can measure it. The ring is pretty worn, I bought a new one and I'll give that a go, it'll be the weekend before I can try it out.

    Monte

  9. #9
    Weird huh?
    Reputation: cmdrpiffle's Avatar
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    48 t front chainring/30 t rear cog. I've done it for 15 years. One of my favorite climbing gears for standing. It's an 8 speed cog, so not as severe as 9 speed, but I do it all the time on the 9 speed as well. (44cr/34c)
    Will it 'wear' the chain/cog/rings out faster? Yeah. I guess. I change the chain about 3 times a year or so and I've got 7 years on the cog/chainrings.
    Cheers,
    Mike

  10. #10
    Chrome Toaster
    Reputation: Hecubus's Avatar
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    No its not cross chaining at all. You should be able to use ALL gears on the middle ring. If its slipping down there might be a problem with your chain or middle ring but more than likely it sounds to me like the front derailleur adjustment might be off as well. The FD acts as a chain stopper. When in the middle ring and 34t cog there should be extrememly little clearance left between the chain and inner plate. Small enough that the derailleur will not allow the chain to drop.

  11. #11
    meh....
    Reputation: Monte's Avatar
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    Quote Originally Posted by Hecubus
    No its not cross chaining at all. You should be able to use ALL gears on the middle ring. If its slipping down there might be a problem with your chain or middle ring but more than likely it sounds to me like the front derailleur adjustment might be off as well. The FD acts as a chain stopper. When in the middle ring and 34t cog there should be extrememly little clearance left between the chain and inner plate. Small enough that the derailleur will not allow the chain to drop.
    The middle ring was pretty worn out, I think that's the problem. The teeth are short and are catching the chain as it goes over the top of the chainring. I don't think you should have to use the FD to keep the chain on the middle ring. I use twist grip, so I can put the FD where I want it, which is usually where it isn't rubbing the chain. I installed a new RF chainring, hope to try it out this weekend.

    Monte

  12. #12
    Chrome Toaster
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    Quote Originally Posted by Monte
    I don't think you should have to use the FD to keep the chain on the middle ring.
    Monte
    No it shouldn't, but when setup and aligned correctly the FD should normally not allow the chain to drop down if it tries to for whatever reason. Since you are using gripshift maybe you're probably giving it an extra click to give more clearance when on the 34t rather than leaving it in the exact center where the clearance will be tight enough to not let it drop.

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