Mod XTR 960 Chainring Holes to Move Mid Ring Outboard?- Mtbr.com
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  1. #1
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    Mod XTR 960 Chainring Holes to Move Mid Ring Outboard?

    If this has already been covered, my apologies, searching not the best with Tapatalk.

    I am running a hacked XTR 960 crankset with a HBC 32T. A 32T is the max the frame with allow with recommended BB spacers. I can almost, almost, see a 33T clearing the stay. For the purposes of this post and in the interest of SS science I don't want to consider other options like spacer juggling or chain stay modification or ...

    I am asking if anyone has modified the 960's crank chainring bolt hole landings by removing material. Don't worry, I have a spare.

    This should move the chainring outboard by the amount of material removed. Of course, it would need to be done accurately, most likely by a buddy with a machine shop (hope he isn't reading this) to ensure a flat/true chainring mount. I would need to add chainring bolt washers to make up for the loss in landing depth. I would also need to move the cog outboard by the same amount.

    Anyone do this or have seen this done? Remember, this is in the interest of SS science!

  2. #2
    one chain loop
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    for the interest of SS science, alignment after removing the material is the least of your worry. shaving 1mm of material seems negligible but is more than enough to compromise safety. losing 1mm material for that female bolt to grab on to is not worth it IMO.
    everything sucks but my vacuum cleaner.

  3. #3
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    In the interest of SS science go for it. sounds to me like you understand that it shouldn't be a hack job and I don't see any problem with the bolts. Have you calculated how much you need to remove in order to clear for a larger ring? ......34...36t. Keep posting with your results. I don't see any safety issue to be concerned with.

  4. #4
    one chain loop
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    yeah, go for it. you only have 3.5mm of material to play with. if you are 2mm off your chainline, no big deal, shave that 2mm. 1.5mm is still safe.

    i mean is this really science or common sense. i'd play with bb spacers any time.
    everything sucks but my vacuum cleaner.

  5. #5
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    Quote Originally Posted by fishcreek View Post
    yeah, go for it. you only have 3.5mm of material to play with. if you are 2mm off your chainline, no big deal, shave that 2mm. 1.5mm is still safe.

    i mean is this really science or common sense. i'd play with bb spacers any time.
    fish creek,
    After you first replied, I thought about it, and I agreed with you. I should of posted that day. The aluminum under the bolt would be too thin and would likely pull through. Not sure what I was thinking.

    Crazy8, thanks for the encouragement.

    [/end_thread]

  6. #6
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    Actually, the way these cranks are set up, there is a cavity that the bolt sits in. My concern would be whether or not that cavity provides reinforcement to the spider arm. I would suspect that you could machine out a good bit of the cavity without impacting spider strength. The cavity is there to provide strength for the big ring. Since you dont have the 44T, then you don't need all of that material. You could then - potentially - machine out part of the chainring so that if fits. Pulling a chainring bolt through anything, would be the least of my concerns - I dont think it could happen... they're far too weak. I think you might be able to make it work, but it seems like a lot more trouble than it's worth when you can buy a set of SLX arms for about a hundred bucks.

    If you have the crankset laying around, I say go for it. Why not? The worst thing that happens is you break your crankset and/or chainring and maybe gouge out a bit of your chainstay and smack your nuts on the top tube or stem.
    Last edited by BShow; 11-16-2011 at 08:16 AM.

  7. #7
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    Quote Originally Posted by fishcreek View Post
    for the interest of SS science, alignment after removing the material is the least of your worry. shaving 1mm of material seems negligible but is more than enough to compromise safety. losing 1mm material for that female bolt to grab on to is not worth it IMO.
    You wouldnt be machining out anything that the chainring bolt contacts.

    I'm thinking cut part of the excess cavity in order to mount a ring from the outside. Cuts could be something like what I have here in red. Maybe also bore out a small portion of the remaining cavity to give enough room to fit the chainring... Blackspire Super Pro looks to have rounded bolt holes that might just work for this.

    <img src="https://img.photobucket.com/albums/v439/BShowWRX/rings2.jpg">
    <img src="https://i.pgcdn.com/pi/77/14/66/771466007_260.jpg">

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