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  1. #1
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    external bb bearings vs. 3 piece crank

    Anybody else think the external bearings are slow compared to the three-piece crank set?
    Currently have the FSA megaexo. Seems pretty doggy compared to my older MB 3 piece crank. After taking the chain off the ring and free spinning the crank produces 4 x more revs. on the 3 piece (10 revs. vs. 40+ revs.) I noticed the same sluggish feeling when I road a yeti with external bb bearings. What would be some options at this point to eliminate the drag? I am probably replacing the external bearings but don't expect that is the real solution. Thanks!

  2. #2
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    I have noticed that the cranks that do not allow indipendent bearing adjustment, ie Race Face Trutatviv and FSA, do not run as smooth as the Shimano External and neither are as smooth as the old three piece. I think that its because on the older setup the bearings are free to spin and did not have as much of the load the external bb has.

    I have not tried them but FSA has a road BB with ceramic bearings that might fit your crankset. If it did it should imrpove the drag.

  3. #3
    bang
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    the drag is most likely caused by the bearing seals. it's normal. once the seals wear out a little, the cranks will spin more smoothly.

  4. #4
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    Quote Originally Posted by Cyco-Dude
    the drag is most likely caused by the bearing seals. it's normal. once the seals wear out a little, the cranks will spin more smoothly.
    It has been two months with almost daily riding. Is more time than that needed?

  5. #5
    Giggitty giggitty!!
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    Quote Originally Posted by broncbuster
    Anybody else think the external bearings are slow compared to the three-piece crank set?
    Currently have the FSA megaexo. Seems pretty doggy compared to my older MB 3 piece crank.
    This is because the spindle is not spinning directly on exposed bearings as it did with conventional style BB's.

    you shouldn't be able to notice this while pedaling though. If you are noticing it then your bearings are most likely seizing or dirty/worn. Putting grease on the spindle of a 2-piece crank is required.

    Quote Originally Posted by forceyoda
    have noticed that the cranks that do not allow indipendent bearing adjustment, ie Race Face Trutatviv and FSA, do not run as smooth as the Shimano External and neither are as smooth as the old three piece
    The Shimano ones spin better because you have to compress the left hand crank arm against the bearing with a compression cap which allows for a [tiny] bit of preload adjustment. Other designs which do not have this will not spin very freely (i.e: RaceFace).

  6. #6
    Harky
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    Quote Originally Posted by dhpimp
    This is because the spindle is not spinning directly on exposed bearings as it did with conventional style BB's.

    you shouldn't be able to notice this while pedaling though. If you are noticing it then your bearings are most likely seizing or dirty/worn. Putting grease on the spindle of a 2-piece crank is required.



    The Shimano ones spin better because you have to compress the left hand crank arm against the bearing with a compression cap which allows for a [tiny] bit of preload adjustment. Other designs which do not have this will not spin very freely (i.e: RaceFace).
    I've got both...the shimano externals and the FSA Megaexo that Bronc is concerned about. I notice a little drag on the FSA's...but they are new...less than 2 mos old.
    The shimanos have been on the trail for 3 years. They spin very freely. I prefer either design to an internal BB cuz I've blown several of them thru hard riding.
    I'm not sure it's a big deal, yet...the crank bearing drag is miniscule compared to other factors like tire rolling resistance and weight, brake drag, chain drag, etc.

  7. #7
    a.k.a. BicycleKicks
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    I had the same issue with my RF Deus. When spun slowly, they would stop abruptly like there was drag at a certain point. So I swapped out the rubber spacers for narrower ones that were provided for this purpose and they spin much better. In fact, I can't really detect any drag now at all. The instructions that came with the cranks explain how to swap the spacers etc. Before I did this, too much side pressure was being exerted on the bearings.
    I read that on the internet.

  8. #8
    I always bleed like this.
    Reputation: PoorBehavior's Avatar
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    I have the Megaexos and without trying to be different, I thought they were VERY smooth. Going back and forth from a shimano square taper and a Truvative GXP (also external) I would notice the difference right away. As far as pre-load goes, on the FSA the bearing are sitting in the cup, as long as you dont screw the arm on too tight they should be very smooth. The difference between too tight and just right was, if I remember corectly, not very large. Maybe a turn or less of that single crank bolt. I would back that bolt out just a hair or two and see if they are any better. That bolt does not need to be tight, all it is for is to get the arm to the right pre-load, the arm is held on by the two bolts at the head of the arm.

  9. #9
    surly and rigid
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    I'll trade some minor almost unknowticeable drag for some super stiff and cheaper to repair cranks, You can pop out those external bearings and get them for 7 bucks a peice at any good bearing shop. Try that with a sealed 3 peice BB.

  10. #10
    Harky
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    Gnome...that's good to know cuz I've got 2 rides with the external bearings!
    I replaced one of my Shimanos a year or so ago when the plastic face shield broke.
    The bearing felt OK but I freaked over it anyway. That one bearing (complete with shell) cost me $30!!
    So they're not exotic??

  11. #11
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    Quote Originally Posted by harky
    I'm not sure it's a big deal, yet...the crank bearing drag is miniscule compared to other factors like tire rolling resistance and weight, brake drag, chain drag, etc.
    Maybe it's body hair/wind drag or am I over thinking this?

  12. #12
    Chrome Toaster
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    Outboard= larger bearings. Larger bearing surface = greater friction. Larger bearing area = more grease needed to lubricate. More grease = more resistance to overcome. Outboard bearings rolling resistance vary among brands and adjustment but they will never roll as freely as three piece crank spindles with tiny bearings. Unless the drag is excessively stiff as in the bearings are sideloaded and they do not spin freely AT ALL I suggest you find something else to worry about.The extra drag is so miniscule it is absolutely irrelevant.

  13. #13
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    Quote Originally Posted by Hecubus
    Outboard= larger bearings. Larger bearing surface = greater friction. Larger bearing area = more grease needed to lubricate. More grease = more resistance to overcome = drag is so miniscule it is absolutely irrelevant.
    Must be new math!
    Last edited by broncbuster; 07-14-2006 at 10:26 AM.

  14. #14
    Chrome Toaster
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    Quote Originally Posted by broncbuster
    Must be new math!
    I was typing in a hurry. You get the idea

  15. #15
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    Quote Originally Posted by broncbuster
    Maybe it's body hair/wind drag or am I over thinking this?

    Isn't it a little hot to be riding in a sweater?

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