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  1. #1
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    xt m770 chain rings compatibilty

    Which chainrings are compatible/not-compatible with the m770 22/32/44 crankset (9-spd xt mega)? Are the triple/double 10-spd chainrings and/or dyna-sys not compatible, even if the bcd is the same? any restrictions with cross-compatiblity among the slx/xt/xtr etc chainrings?

  2. #2
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    I might have the same question...

    I am thinking it's time to replace my middle and granny rings but can't figure which of the letter-number combos from shimano apply to my setup....or if it matters. I'd be interested in the responses as well.
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  3. #3
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    You can use any 9/10 speed chainrings with a 104 BCD for the 32/44 positions and 64 BCD for the inner. They can be SRAM, Race Face, Shimano, doesn't matter.

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    cool

    thanks ryguy. The replacement m770 ring is silver and has these black kidney shaped plates bonded to the ring that look like they are sure to catch crud and are missing from the rings I'm replacing.

  5. #5
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    Quote Originally Posted by nineracerxer View Post
    thanks ryguy. The replacement m770 ring is silver and has these black kidney shaped plates bonded to the ring that look like they are sure to catch crud and are missing from the rings I'm replacing.
    The 770 cranks and 780 cranks have funny shaped shoulders on the middle ring and offset spacing on the big ring. Not quite a plug and play swap.

    You should be able to swap any granny ring and middle ring, the change of shoulder shape might cause creaking overtime and I'd be sure to use steel chainring bolts since there will be less support for the chainring on the spider.

    The big ring will need to be Shimano. I'm guessing for weight reductions, XT cranks have a narrower spider between the middle and big rings. The teeth on the big ring are slightly offset so that the teeth spacing between gears stays at the standard 5mm.

    I believe that Raceface makes rings that have the correct spacing if you're wanting to replace the full triple. If not, the M760 36T and 24T rings bolt up and make for a nice 2x conversion - you'll only lose your two biggest gears.

  6. #6
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    For my case, I'd like to keep the triple setup, but reduce the 44t big ring to something smaller. My concern, as you mentioned, will be the shoulder shape even if it were a shimano 104 bcd. I've looked at universal's and there seems to be a few 104 bcd option, but they aren't necessarily designated for the m770 9 spd. Even the 42t big ring for the m780 might not be a plug and play. And even if it is, will there be any issue with the front derailler, or will it just require minor adjustments? Thanks!

  7. #7
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    If you are already contemplating a smaller ring up front, play with the gear inch calculator here:
    Sheldon Brown's Bicycle Gear Calculator

    24/36 setup loses nothing on the low end (~2 gear inches, not very noticeable) and1-2 gears on the high end depending on the cassette size when changing from a 22/32/44 setup.

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    Thanks again GTScoob! I'm still undecided/unsure about having to replace other components (shifters, deraillers, crankset) when converting to 2x more than losing the 3x option, at least for now. Got some other upgrades in mind first (wider bar, shorter stem ), before upgrading some drive train components. I really don't mind my 3x9 setup. Just toying with the idea of going with a smaller big ring as that wouldnt be too $$$, and I'll eventually have to replace those anyway.

    Kinda hoping to go with a medium cage rear der when that needs replacing as well, so that'll def affect how the front gets setup.

  9. #9
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    Thats the beauty of a double conversion like what you're trying to do (and following in the footsteps of plenty of folks over the years). You already have the crank, shifters, and derailleurs to go to a double up front - just remove your big ring and reset your front derailleur high limit screw.

    Folks who know what gearing they want/need for their given terrain have been preaching doubles with or without a bashguard for a longtime. The triple is a one-size-fits-all option but suffers front shifting due to a middle ring needing to be optimized for shifting both ways, lower ground clearance, slower rear shifting due to a longer chain and longer derailleur, and more weight due to longer chain, longer derailleur, and extra gearing.

    For your converted double, you'll just need the chainrings that you choose to use. If you grab a bashguard you can reuse your chainring bolts, otherwise you'll need some singlespeed chainring bolts for the middle ring (new big ring). Your front shifter will still work the same, you'll just be locked out of the third position - 1 will still be your granny and 2 will still be your middle/big ring, high limit screws will keep you from being able to click the shifter into the third position.

    In general short cage derailleurs are great for 1x setups, medium cage derailleurs are great for 2x setups, and long cage derailleurs are great for 3x setups. A really wide range cassette in the back might require the use of a longer derailleur to take up the slop - 1x drivetrains with 36 or larger cogs in the back need a medium cage, 2x with 36T or larger cogs in the back need a long cage. If you dont care about the cage bunching up on small/small combinations you can run a shorter cage derailleur as well.

  10. #10
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    Hmm, now this seems easier than I thought. And since the shifters, front der, and cranks don't need to be replaced, I may do this sooner rather than later. Likely still after I upgrade the bars and stem though.

    So it looks like there is a 26/36/48 combo for the xt m770 9-sp. I can probably get just the 26/36 rings. That should hopefully make it plug and play. The big ring I'd like to replace with a bashguard / chain tensioner, if there is such thing. I'll probably have to do more reading on that.

    And with the 26/36, it's looking like a medium cage rear der is possible even with the cshg61. If my math is correct, using the simple formula in the sticky thread in this sub-forum, this should just be a link over the 33 spec for a shimano med cage, which is apparently conservative. And if I end up just mounting the 36t from the cshg61 to the csm770, take out the 11t it puts it right at the 33 spec. Anything that I might be missing?


  11. #11
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    You'll miss your low end if you go to 26 on the small ring. 22 with an 11-34 cassette or 24 with 11-36 works a little better.... ..... Is what I think.

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    Quote Originally Posted by Scott In MD View Post
    You'll miss your low end if you go to 26 on the small ring. 22 with an 11-34 cassette or 24 with 11-36 works a little better.... ..... Is what I think.
    Definitely check the gear inch calculator I linked above. Bumping from a 22 to a 26 on the low end will effectively remove your lowest gear. If you tend to ride in the 22/32 or 22/34 gear on steep or long grades then you may want to look into another option for the granny (22 or 24T). If you dont ever use that lowest gear then you'll be fine.

    24/36 is probably the most common size for trail doubles but some folks like 22/36, you just have a little worse front shifting.

  13. #13
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    Yeah, I'll definitely miss the 32/34 combo. Just had the 26/36 in mind as those were the optional chain rings for the m770, and I'm kinda hoping for a plug and play solution. I also thought that maybe a 36t cog at the back will mitigate the 26 small ring up front. But I guess that may not be the case. What specific parameter should I be comparing in the gear calculator?

    Apprecaite your help and time on this guys!

  14. #14
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    CR online and plenty of other suppliers sell the Shimano SLX 660 matched 36-22 chainrings for less than $50. With a bash guard and and 11-34 cassette you will be good to go.

  15. #15
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    I Went back to a triple after my conversion. I had a 24 front and 34 rear for my granny and that was not quite enough for the steep climbs I do. If you want the 36 rear I think you have to get a 10 speed cassette. I do not know how lighter a bash guard is than a 44 ring. My 44 ring is my bash guard and still comes in handy if I finish a ride on the road. Your chain does not need much grip on the ring going down hill. Do the conversion if shifting is you priority. I am a bit of a challenged mechanic so my shifting never gets real good anyway.

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