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  1. #1
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    Mechanical weirdness: XT crank set chainrings?

    A friend and I built up three Mojos recently, with parts shipped from Ibis. Two had XT cranks and one had XTR.

    Right after building, both bikes with XT crank sets have a strange click/clack/clunk sound on each pedal stroke, when decent force is applied. You could also feel it in the pedals. It happens on both the middle and big chainrings, and on most of the smaller rear cogs. In other words under a good pedaling load.

    We think we might have narrowed it down to the way the XT chainrings' teeth are cut/shaped. It does seem to be getting better on the bike that is being ridden. Has anyone else noticed this?

    Steve

  2. #2
    Mojo0115
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    My wife has a mojo with XT cranks and it was silent running for her.

  3. #3
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    No. Not pedals (though that would get worse with riding).

  4. #4
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    I had to replace my middle chainring after about 12 rides. Apparently Shimano tried some design to reduce chain suck and caused the chainring to wear out. They replaced it, but it took a week and the last few rides had some scary climbs as the chain skip on the chainring.

  5. #5
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    Quote Originally Posted by sdold
    A friend and I built up three Mojos recently, with parts shipped from Ibis. Two had XT cranks and one had XTR.

    Right after building, both bikes with XT crank sets have a strange click/clack/clunk sound on each pedal stroke, when decent force is applied. You could also feel it in the pedals. It happens on both the middle and big chainrings, and on most of the smaller rear cogs. In other words under a good pedaling load.

    We think we might have narrowed it down to the way the XT chainrings' teeth are cut/shaped. It does seem to be getting better on the bike that is being ridden. Has anyone else noticed this?

    Steve
    Hello Steve,

    Tom from Ibis posting. Shimano had a design issue on some of their '06 XT cranks. Check the date code stamped on the inside of the driveside crank arm around the pedal spindle hole. It should be a two letter code like EL or FI or something. The first letter stands for the year, E = 2006, and the second letter is the month. Anything earlier than EI (September, 2006) may be a problem. And you should contact Shimano directly about getting replacement chainrings.

    Hope this helps!

  6. #6
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    Thanks Tom, they are both EL. We're still looking for the noise, but we've decided that it's not too big a deal. Mostly just irritated with ourselves that we can't figure out what it is

  7. #7
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    I have the xtr chain rings and have the same problem, it's driving me crazy, I have had a ton or mechanics look at it. I also get chain suck at least once on every ride over 4 hours, that is driving me crazy too, let me know if you find a solution. I was thinking it's needs spacer or something?

  8. #8
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    well, I have a LX Crankset which has a no of EC, is this listed into Shimano chainring problem?

  9. #9
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    Drivetrain noise...

    Steve:
    I have seen some cases where bikes with new Shimano chains and new SRAM cassettes have made some strange noises like you are describing.
    A buddy of mine spent quite a bit of time figureing out what might be causing it.
    Looks like the chain is hanging onto the smaller cogs on the cassette and making a audible noise and clicking sensation as the pin and roller depart forward on their way toward the front chainrings.
    This is only happening in the smaller cogs (outer 3 or 4 cogs).
    As the chain and cogs "break in" this situation should solve itself.

    Rick from Bicycle Engineering/Tango Tandems.

  10. #10
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    I used to have some noise coming from the drivetrain of my Mojo as soon as I switched from a Truvativ Stylo to an 07 M970 XTR crankset. A fairly noticeable "mechanical" sound which was pretty much constant. However, the sounds slowly diminished until they pretty much disappeared.
    Last edited by Carbon Ken; 06-22-2007 at 11:12 AM.

  11. #11
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    I had a similar clacking noise in certain gears. I am using an XT front derailleur and found that in certain gears the excess derailleur cable touched the chain and made a strange sound that seemed like it was coming from the cranks or bb. Simple fix was to bend the excess front d. cable in the other direction and now my bike is silent in all gears.
    Last edited by hrdude; 06-23-2007 at 11:44 AM.

  12. #12
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    Rick: I'm not 100% positive that it was caused by the links coming off the cogs, but I'm just about 100% sure it was something going on between the chain and the cogs. When we were running the drivetrain on the stand I could feel movement between the chain and cogs that coincided with the bumps we felt in the crank, so I think it has to do with the chain fits the cassette cogs, but I'm not sure it's the side clearance. At any rate it seems to be going away, so I'm not too worried about it. I didn't notice it on Tim's bike when we were riding it around the lot at the airport and it's just about gone on mine.

  13. #13
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    The "problem" is gone, after a few miles the noise went away. I guess it's not a big deal.

    Hey Rick, I carried the Mojo on my back for 1/2 miles of boulders on a 45 degree slope today on the shore of Folsom Lake after taking the wrong trail. I was literally trekking across 1-foot dia rocks that would sometimes roll 50 feet down into the lake. If I'd have dropped the bike it would have gone into the lake too. It was my worst ride ever, but it's great to have a light bike :-)

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