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  1. #1
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    Pivot Mach 5.7 Carbon Ghost Shifting

    Hi, I'm wondering if anybody else has experienced this annoying problem on their Pivot Mach 5.7c ?

    I have a near-new 2x10 XT/XTR build of the 5.7c and when going fast over sections of rough/bumpy trails in top gear (big ring front, small rear cog) the chain is forever jumping to the second smallest cog for a split second... up,down,up,down,up,down constantly until the track smooths out. Never happens at slow speeds, over big bumps or peddling hard uphill, only when going at speed over lots (and lots) of small bumps and rocks. Not easy to watch what the derailleur is doing during these moments, so I can't really make any comments there, but I'm thinking maybe the derailleur cage is simply shaking/vibrating enough to move the chain to the next cog for a couple of teeth, then coming back.

    The limit screws are all set ok, the shifter cable doesn't have any tension in it when the chain is in the small cog, and this doesn't change when the suspension is fully compressed. The cable outers couldn't be made much shorter if I tried. Everything is brand new, nothing is bent.

    Any suggestions? The shop doesn't know ("it doesn't happen on the workstand, it must be ok") so short of ditching the Shimano stuff for the much superior (in my opinion) SRAM X0 that I've never had an issue with on my old Specialized Epic, is there anything I can do about this?

    Other than this, my Mach 5.7 has gotta be one of the best bikes money can buy.

    Cheers,
    Pinchflat66

  2. #2
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    Do you have a clutch type rear derailleur? If so, is the clutch switch on or off? Also, maybe a chain guide would help take up some slack in the chain? Sound like the turbulence is making the chain jump over the teeth on the sprockets which is an odd problem to have unless there's something wrong with the chain, cassette, or rear derailleur. Maybe take it to another bike shop/mechanic for another opinion? Dunno if this is helpful or not but, hey, we're brainstorming here =)

  3. #3
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    Hmmm, weird. Usually happens with warn cassettes, but your's is new. Shimano doesn't have nearly the number of warranty issues SRAM has, but a bad derailleur can always make it into the box. Could also be something funky with the cable. Could also be a bent hanger. Might also be the chain. You using a Shimano chain? Lot's of maybe's; I'd take it to another shop - one that really is into trouble shooting.

    Oh, and to answer your question, no haven't heard of this with other 5.7c builds. Only issue I had with my XTR was it blowing up against the rock it landed on at high speed and, well, no derailleur would have survived that hit. :^) Good luck - sure we'll all be curious what the actual issue is.

  4. #4
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    Meesta Seeds, yes, it's a clutch type rear derailleur and I always have it switched on. I've never run a chain guide on any of my bikes before, so I'm a bit clueless as to what sort I'd need for the 5.7. I thought the clutch type derailleurs did away with the need for a chain guide.
    I might see if someone from my Saturday morning group can sit closely behind me and watch what the derailleur is doing when it has these moments (not too many places to mount a camera back there).
    Failing that, yes, a more competent bike shop might be on the cards.

  5. #5
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    Did you measure your chain when you put the new components on? It may be too long.

    Do you have new tires? Ones that have wide side knobs. Perhaps your chain is slapping the side of the tread which in turn is making it jump at higher speeds. I typically wouldn't consider this based on the gear you suggested it's happening in....just considering all options.

    Cassette lock ring is tight? Do you have any type of spacer on the cassette body?

    Rocker and pivot bearings properly torqued? Any laterally play?
    AKA: G-wat

  6. #6
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    Bugaroo, everything is new, even the tires. The Shimano chain is definately not too long... actually it's too short and will probably destroy the derailleur if I happen to fully compress the rear suspension when I'm in big ring and big cog, but I think that's highly unlikely. Everything felt tight when I first got the bike a month ago, but I guess another check wouldn't hurt...
    A friend suggested that the upper jockey wheel is way too close (6mm, 1/4 inch) to the cassette, so I'll see tomorrow what, if any, difference a few more mm makes.
    Thanks everybody for all your suggestions.

  7. #7
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    Pivot Mach 5.7 Carbon Ghost Shifting

    I remember reading somewhere that after while the clutch on the derailleur needs adjusted. I believe the XTR comes complete with the tool. May be worth a look into this. I have an XT Shadow+ and recently noticed that my lower jockey wheel had popped out of true. A mechanic at a local race popped it back in. It was throwing my chain off just a bit. Sometimes the small things are the most annoying. Hope this helps.

  8. #8
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    Adding more distance between the upper jockey wheel and the cassette actually made it worse... so much for that idea.
    A friend with a Mach 4 reckons he had exactly the same problem on his bike, and it was caused by a bent hanger, as per what JMW503 suggested might be wrong. It all looks fine using the eyeball method but hey, any excuse to buy a new tool, so a Park Tool DAG-2 is on its way. Unfortunately the same friend's DAG-1 doesn't fit on my bike, due to the (manufactured) kink in the hanger, but the DAG-2 has a longer and narrower alignment boss that hopefully gets around this problem. If not, my DAG-2 just might have to be given a bit more narrowing courtesy of a file.

  9. #9
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    I've had something like this happen as well, in addition to usual bent hangers and other stuff. I have had to glue the on end caps on the middle part of gear housing to stop ghost shifting. Seems that I had used end caps for different housing so they did not hold in place and moved constantly as suspension moved.

    Also the middle part of the gear cable outer needs to be just the right length, about 5-10 mm longer than bare minimum works best for me.

  10. #10
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    My Park Tool DAG-2 finally arrived in the mail yesterday and, after tiny a bit of filing of the hanger to allow it to fit, it revealed that the hanger was indeed bent! Quite a lot in fact. With the DAG at the 6 o'clock position and the rod barely touching the rim, it was hitting the spokes at the 12 o'clock position! The 3 o'clock and 9 o'clock measurements were spot on. A gentle heave on the DAG straightened the hanger, and a quick readjustment of the derailleur and all seems good.

    Everyone should have access to a DAG-2. It's brilliant. I've always relied on the good old eyeball test, but never again. Oh, and even on a brand-new bike straight from the shop it pays to check.

    Now for a test ride....

  11. #11
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    Quote Originally Posted by Pinchflat66 View Post
    Everyone should have access to a DAG-2. It's brilliant. I've always relied on the good old eyeball test, but never again. Oh, and even on a brand-new bike straight from the shop it pays to check.
    Eyeball test works if you remove the hanger from the bike and lay it on a table... takes just few minutes. DAG-2 is a nice tool though.

    My latest bent hanger was due too short chain after trying different chainrings and riding into g-out... the hanger was bent in at least 3 dimensions (joking) but appeared quite ok the bike. However, once it was removed from the bike it was easy to see how crooked it is.

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