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  1. #1
    Too busy looking good
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    XTR cranks w/ external bearnings, excessive friction?

    I have XTR M960 cranks with external bearings on my main bike, and an older XT crankset with a traditional BB on my beater/commuter bike. I had the chains off both recently, and noticed that if I give both cranks a spin and allow them to rotate freely, the XT cranks spins much longer than the XTR. My XTR cranks stop almost immediately after a decent nudge, but the XT cranks complete a full revolution before stopping.

    My XTR bearing cups are just a few month old, and they're installed correctly. Has anyone else observed what seems to be excessive friction in their external bearing Shimano cranks, especially in comparision to billet-style BBs? I wonder if this is normal or typical, maybe I got some bad bearing cups, or maybe they need to be broken in some more?

  2. #2
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    Maybe

    the non-drive side crank was installed (pseudo-preloaded by that plastic knobbie) too much. You're only supposed to finger tighten the plastic tool...

  3. #3
    sugoi chairinko
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    Check your seals, I know mine aren't perfectly sealed to the weather, and after a muddy ride or long bath the moisture that builds up tends to make them drag a bit. I use a syngrease gun and purge the moisture, then they seem to spin better. I heard that early m960 cranks had a problem, but that it was remedied, so maybe I'm way off base...

  4. #4
    I meant to do that
    Reputation: sethm's Avatar
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    Are you supposed to be able to pop the covers off the bearings?

  5. #5
    sugoi chairinko
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    Quote Originally Posted by sethm
    Are you supposed to be able to pop the covers off the bearings?

    Sorry Sethm, I've been out of town. I haven't done it for awhile, but if my memory serves me correctly, ( sometimes it doesn't serve me at all, so take it with a grain of salt) they are removable, because I've done it a few times without much trouble. Someone else may have a more educated oppinion.

  6. #6
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    Quote Originally Posted by sethm
    Are you supposed to be able to pop the covers off the bearings?
    People do it but its not meant to be serviceable and sometimes the plastic cover will crack when you try.

    My vote is with Flip'n, i think there is too much bearing preload. Loosen up the preload and see if they spin any better.

  7. #7
    3 "fiddy" for short
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    Look HERE to see how to service the external cups. This is a great post and much thanks to the author.

  8. #8
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    Check the frame prep also

    Were the faces of BB shell faced to clean/true them up before assembly? If not, that can cause misalignment of the bearings that will show up as increased drag and premature wear.

  9. #9
    MTB B'dos
    Reputation: LyNx's Avatar
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    HOser the external Hollowtech2 cranks don't spin very much at all even when installed correctly, not even close to how an older square taper, HT1 splined BB will spin. You should get about a revolution and maybe a bit more though, so maybe make sure you tightened the cups to the right torque and didn't over tighten them and then make sure you only finger tightened the plastic tensioner piece on the left crank.

    Quote Originally Posted by HOser
    I have XTR M960 cranks with external bearings on my main bike, and an older XT crankset with a traditional BB on my beater/commuter bike. I had the chains off both recently, and noticed that if I give both cranks a spin and allow them to rotate freely, the XT cranks spins much longer than the XTR. My XTR cranks stop almost immediately after a decent nudge, but the XT cranks complete a full revolution before stopping.

    My XTR bearing cups are just a few month old, and they're installed correctly. Has anyone else observed what seems to be excessive friction in their external bearing Shimano cranks, especially in comparision to billet-style BBs? I wonder if this is normal or typical, maybe I got some bad bearing cups, or maybe they need to be broken in some more?
    Last edited by LyNx; 01-22-2006 at 11:50 AM.
    One day your life will flash before your eyes, will it be worth watching??
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  10. #10
    Pedalphile
    Reputation: HPilot's Avatar
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    Welcome to the club!

    Quote Originally Posted by HOser
    I have XTR M960 cranks with external bearings on my main bike, and an older XT crankset with a traditional BB on my beater/commuter bike. I had the chains off both recently, and noticed that if I give both cranks a spin and allow them to rotate freely, the XT cranks spins much longer than the XTR. My XTR cranks stop almost immediately after a decent nudge, but the XT cranks complete a full revolution before stopping.

    My XTR bearing cups are just a few month old, and they're installed correctly. Has anyone else observed what seems to be excessive friction in their external bearing Shimano cranks, especially in comparision to billet-style BBs? I wonder if this is normal or typical, maybe I got some bad bearing cups, or maybe they need to be broken in some more?
    XTR bb is a piece of crap! Mine, with 250 miles and only 4 months of use had a crapped out non-drive side cup that had to be replaced to the tune of $25. At $25/side- that's a pretty expensive BB for as little material included. It is written all over about the failure of the bearings in Shimano's external cup design. My XT external bb cups are going strong, but haven't seen a lot of off road since install. I use my old hardtail for road training.
    [SIZE=3]"A witty saying proves nothing."- Voltaire[/SIZE]


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  11. #11
    Chrome Toaster
    Reputation: Hecubus's Avatar
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    Ouboard bearings will never roll around as much as traditional sindle type bottom brackets. The bearings are much bigger and will drag more.

  12. #12
    Chrome Toaster
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    Quote Originally Posted by HPilot
    . It is written all over about the failure of the bearings in Shimano's external cup design.
    Uhm not really. Its well known that almost all that have failed have been due to lubrication problems. Most of those failed bearings are in fact not even failed at all. They are just out of lubricant. Take out the grease out of one of them and try to turn it. It will practically seize. The only problem with these cups is that they are claimed to be user non-serviceable which in fact they are and VERY easily so. When they're well lubricated these bearings can last almost indefinately. Myself and many others have had the original bearings for over 3 years and they still roll good as new. I check them about every season or so to see how the grease level is doing.

    I also have a set of Race Face x-type cranks which I had almost seize on me almost solid after 6 months. Turning the cranks felt so stiff it felt like the BB shell was going to be ripped out. I got home and checked the bearings and it turned out that the factory grease had washed away completely. There was not a gram left in there. I packed them up with good grease again and like magic they started working even better than new again.

  13. #13
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    Yeh I'd have to agree with Hecubus on this. Haven't had mine (XT) for 3 years like Hecubus, but I have had them for about 6 months with some seriously nasty off road conditions (about 600-700 miles) and they are still working great.

    Hecubus, thanks for the heads up on being able to regrease them, next time I have the crankset off and BB's out for a check I think I'll check the grease in the cups.



    Quote Originally Posted by Hecubus
    Uhm not really. Its well known that almost all that have failed have been due to lubrication problems. Most of those failed bearings are in fact not even failed at all. They are just out of lubricant. Take out the grease out of one of them and try to turn it. It will practically seize. The only problem with these cups is that they are claimed to be user non-serviceable which in fact they are and VERY easily so. When they're well lubricated these bearings can last almost indefinately. Myself and many others have had the original bearings for over 3 years and they still roll good as new. I check them about every season or so to see how the grease level is doing.

    I also have a set of Race Face x-type cranks which I had almost seize on me almost solid after 6 months. Turning the cranks felt so stiff it felt like the BB shell was going to be ripped out. I got home and checked the bearings and it turned out that the factory grease had washed away completely. There was not a gram left in there. I packed them up with good grease again and like magic they started working even better than new again.
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  14. #14
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    mine act the same way. i was thinking things would loosen up after a few rides. i was wondering, does this friction or whatever it is, add resistance when you are pedaling?

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