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  1. #1
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    Shifting issues on xt m785 2x crank.

    I just installed a new 785 crank (26/38)on my tallboy lt. I switched out the chainrings with a set of Middleburn rings because I wanted a 36 tooth big ring. I also added a new Blackspire bashring (36 tooth)made for the 785. I have an xtr 2x front derailleur on it and xtr shifters. After setting the clearance on the fd according to shimano specs, it will not shift to the big ring because it hits the edge of the bashring. I have to raise the clearance to about 1/4" or more in order to make it clear the bashring. It still doesn't shift right though. It slips quite a bit before it completes the shift. The LBS looked at it and they think its because of the chainrings not having as many shift pins and ramps as the shimano chainrings. Does anyone here have any ideas? I think it's because of the excess fd clearance although the bashring is suppose to work with this exact setup. I may have to ditch the 36 tooth ring and bashring and just go to the stock 38 tooth so I can lower the clearance on the fd. Is there another 36 tooth ring out there that should shift better? The Middleburns worked fine on my 3x10 setup. I really would like to retain the bashring if possible.

    Thx
    Dave

  2. #2
    Trail Tire TV on blogger
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    I'd try a Blackspire. I've switched out both Sram and Shimmy rings for them and get as good or better front shifting with them.

    like to see a pic as the 36 bash and ring should be close to level so why is the derail hitting? ?
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  3. #3
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    Try it without the bashring - prove which theory is correct.

  4. #4
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    Shifting issues on xt m785 2x crank.

    Moving the derailleur for bash guard clearance seems to be causing the problem. Those XT double cranksets are designed to work sans guard. I am not 100% sure, but I world try running it without the guard and put the derailleur where it should be. That should fix it.


    Sent from my iPhone using Tapatalk 2

  5. #5
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    Shifting issues on xt m785 2x crank.

    Thanks for the replies. I am going to try it without the bashring. If that doesn't work then I'll put the factory chainrings back on it. It looks like the bashring is the same size as my 36 tooth gear with the chain on it. It's a little bigger than the ring itself. It's suppose to be specifically for this size ring. The fd instructions say to set the clearance between 1&3mm off the chainring. No way that can work without contacting the bashring. Right now the bike is at the LBS getting the frame replaced under warranty. Had a small crack on the rear shock bracket. It will be a little while before I get to play with the fd/bashring. I'll post back what fixes it. I may call Blackspire in the meantime.

    Thx
    Dave

  6. #6
    Poacher
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    I use Blackspire 34 as large ring, no problem. But no bash ring, and I kept the 26 in place. This is for 26 inch wheel bike.

  7. #7
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    Shifting issues on xt m785 2x crank.

    I called Blackspire about my issue. They said just to fiddle with it until I got it right. They said when the front derailleur is adjusted properly, it should clear the bashring by about 1/2 of a millimeter. In order for mine to clear, it's over a 1/4" above the chainring. Is it possible for one brand of ring to be smaller in diameter than another brand with the same number of teeth? I hope to have the frame replaced by the weekend so I can mess with it and get it shifting right.

  8. #8
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    You didn't accidentally order a single speed ring did you? Or a 9 speed width? The new 10 speed chains are quite narrow i think, and the Blackspire single speed ring on my ss has long teeth. Blackspire on my gear bike is entirely different. Just checking.

  9. #9
    Poacher
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    My Blackspire Super Pro 104 34 on gear bike does have ramps and pins too. The single speed ring from Blackspire MonoVeloce does not.
    Last edited by hoolie; 05-25-2013 at 12:34 PM.

  10. #10
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    Shifting issues on xt m785 2x crank.

    Well I got the bike back and found out the issue is with the chainring. Put the shimano 38 tooth on it and it shifts perfect. I did leave the Blackspire bashring on it even though its for a 36 tooth ring. It is the same size as the 38 tooth ring without the chain on it so it ought to still protect it well enough. I may try the Blackspire 34 or 36 chainring in the future as it seems most thing they shift better. My 34 tooth middleburn ring worked great on my 3x but I guess the extra size of the 36 tooth just doesn't let it work on my 2x setup as well.

    Dave

  11. #11
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    Shifting issues on xt m785 2x crank.

    Ok, after riding it a little more, it's back to not shifting from the small ring to the bigger one. It actually is worse than ever. It will just keep slipping until I shift back to low and then it drops the chain to the inside. New gears, new chain and new derailleur. It's clearing the bashring just fine so I know that's not it. It fails to shift from low to high regardless what gear it's in on the rear cassette. Guess that proves the shimano chainring doesn't work any better than anything else.

  12. #12
    Poacher
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    Your shifter pod can be set for 2 or 3 speed. My Turner 5 spot has you cut a part off front derailler for clearance(interference with frame). Your cable not slipping and tensioned correctly? Housing bottomed out into holders. Start over with limit screws all the way out and get chain off to side to see if derailler is moving side to side all the way. Bottom bracket spacers correct? Chain too short(36 rear cog is HUGE). I have been working on bikes for 30 years, but sometimes I will forget something as I only do drive train every few yrs, as opposed to bike mechanic that does it every day.

  13. #13
    Rub it............
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    Go back to basics.

    Check limit screws and cable tension.

    With the bike being practically new again - new frame, a few rides = adjustments needed again

  14. #14
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    Quote Originally Posted by berettadave View Post
    I called Blackspire about my issue. They said just to fiddle with it until I got it right. They said when the front derailleur is adjusted properly, it should clear the bashring by about 1/2 of a millimeter. In order for mine to clear, it's over a 1/4" above the chainring. Is it possible for one brand of ring to be smaller in diameter than another brand with the same number of teeth? I hope to have the frame replaced by the weekend so I can mess with it and get it shifting right.
    If your bike is a full-suspension you might need to have a bigger clearance of the fd above the chainring/bashguard. When you sit on the bike it compresses under your weight and the chain moves to a higher position in the cage.

    I've recentrly installed a 24/36 combo with a bash on a Reign and it took me a while to find a workable setting of the fd. It you set it too low, the shift from the smaller ring is problematic - the crank makes several rotations before the chain engages the bigger ring or it just doesn't shift at all.

    As well, you should check the High/Low settings - perhaps loosen the High adjustment screw just a bit to enable the cage to move a bit farther when shifting to the big ring.

  15. #15
    Poacher
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    Rode with Blaine yesterday, he is using OLDER 3 x 10, XTR shifter, and new 2 x 10 front. He was showing me that the cable needs ALOT of slack in it while in smaller front ring. Then, when he shifts to big ring, it is in proper orientation. I was amazed at how loose cable was, and he explained how it needs that slack to shift correctly when using 2 x 10 chain rings, with old style XTR 3 x 10 shifter.

  16. #16
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    Shifting issues on xt m785 2x crank.

    I've messed with it a little more and I think I have it figured out. The Middleburn 36 tooth ring definitely did not have the pronounced ramps that the Shimano 38 tooth ring has and not nearly as many pins for picking up the chain. The problem with the shifting on the Shimano ring was due to the LBS's incorrect routing of the shifter cable. This new XTR shifter is a little different than what the tech documents show.
    It has the cable pinch bolt that threads in facing forward rather than threading in from the crank side(kinda hard to explain). I called Shimano and talked to a tech there. He said the tech documents aren't updated yet to show the new derailleur. The problem was that the cable was routed down and directly around the pinch bolt like on the older derailleur rather than around the outer bolt shroud and then under the head of the bolt. I changed it and now it shifts great. Shifter feels like it takes less effort to shift too. Looks like it was throwing the geometry off. Can't really blame the shop as the documents shipped with the derailleur don't even show the one I bought.

    Thanks for the help. Now I'm going to try a Blackspire 36 tooth ring and see if it works too.

    Dave

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