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  1. #1
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    New XT Crank/BB: does the BB need to be broken in?

    Anybody installed a new set of M760 cranks? I just did and dang that BB is difficult to rotate. I haven't ridden it yet, but it definitely does not spin freely. I don't think I overtorqued the cups/bearings. Perhaps it needs to break in?

  2. #2
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    How tight did you secure the non drive side star cap thing? According to Shimano/Park Tools it only needs to be torqued to 4-6 in-lbs. Other than greasing the obvious areas, I can't think of anything else.. Just try riding it and see what happens.

    And check this for more explicit installation instructions:
    http://www.parktool.com/repair_help/bbt9.shtml

  3. #3
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    I installed an XT M760 crankset about 2-3 weeks ago, and I've had no problems with it. Not sure what else to suggest--I just downloaded the instructions from the internet and followed them verbatim.

    Post back here when you figure out what's happening--it'd be nice to know... G'luck bro!
    waaahoooooooooooooooooo

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  4. #4
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    Quote Originally Posted by burndtjamb
    How tight did you secure the non drive side star cap thing?
    I secured it just barely past "finger tight". Thanks for the link.

  5. #5
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    Its normal for them to not spin freely at first. The seals in the bearings and cups drag a lot for the first few rides while they break in.

  6. #6
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    Update

    Thanks for the advice.

    Turns out it was my fault. The frame I'm putting these in is an '03 GF X-Caliber. I looked at the documentation for the frame which said the BB was 73mm. I asked some other people on here what it was ... they said 73mm. Searched the forums for the size, bunch of posts said it was 73mm. (I did all that before getting the frame). So I relied on that when I should have just measured it myself once I got the frame. Turns out that its 68mm!

    I'm assuming that the BB was faced down to 68mm from 73mm. Didn't know that could happen, but I can't explain it otherwise.

    So once I had that figured out, I setup the correct spacers and no problem. Unfortunately the plastic tube got slightly deformed during the 73mm-installation-that-should-have-been-68mm-installation ... but I'm not too worried about that.

  7. #7
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    Thats very weird. I've never seen one of those GF frames with a 68mm bb shell. Must have definately been faced down to 68mm. I should have thought of that. I saw similar things happen a lot in the early months of the outboard bearing cranks. People didn't quite yet understand the concept of the spacers so they just left them out and crushed the inner tube. Result is the crushed tube dragged like crazy against the spindle. You can use it without the tube for now if you damaged it but I very strongly recommend you install it or replace it with one that is in good condition. Not using it will eventually cause the spingle to rust and its going to be little fun to remove it if it does. You can buy it seperately for just a few bucks.

  8. #8
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    Quote Originally Posted by Hecubus
    You can buy it seperately for just a few bucks.
    Sounds like you've seen it for sale somewhere ... can you point me towards where I could find it? Would appreciate it!

    BTW, the tube was only slightly deformed and I think its going to do its job. However, if I can find an easy replacement I probably will change it out.

  9. #9
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    Quote Originally Posted by Suicyco
    Sounds like you've seen it for sale somewhere ... can you point me towards where I could find it? Would appreciate it!

    BTW, the tube was only slightly deformed and I think its going to do its job. However, if I can find an easy replacement I probably will change it out.
    Any online dealer or bike shop with the QBP catalogue can get it (aebike.com, bikeman.com for example). Its about $3. If you reuse the damaged one just make sure the orings can engage fully and that its completely sealed. You just need to make sure moisture and water that accumulates inside the frame doesn't make it to the spindle.

  10. #10
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