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  1. #1
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    Bottom-brackets, old ways better?

    So I'm rebuilding a friend's bike -- an old, Bianchi Avenue hybrid.

    Last night I cleaned and regreased his bottom-bracket bearings. First time I've ever worked on a cup-and-cone bottom-bracket.

    A good spin of his cranks now easily nets me a over a dozen revolutions of the pedals. I just got 14 revolutions without trying hard.

    By contrast, none of my newer and "better" bikes even comes close. I have three bikes with Shimano XT external-bearing bottom-brackets, and I'm not sure I even get three revolutions of the pedals when I spin their cranks. I certainly get nowhere near a dozen.

    I'm sitting here now, wondering how much of my energy is lost in spinning my XT cranks and whether it might be a good idea to go and invest in some square-taper cranks and bottom-brackets. (Not sure I can find cup-and-cone for mountain-bikes).

    I'm looking at this 10-year-old bike, and I'm thinking that perhaps the industry has gone backwards rather than forwards here.

  2. #2
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    At the risk of sounding like a retro grouch, you've "discovered" what most of us over 35 have known for years. Much of the progress in BB's has been backwards.

    Time was when the original BB would still be in service when the frame went to the scrap heap. In many cases that was without any service.

    Part of the impetus for the move to cartridges came from the bike builders who wanted to get away from the time and skill involved in assembling BB's into the frame. Hence the cartridge, shipped pre-adjusted (non-adjustable) and ready to just drop in by any monkey on the assembly line.

    I should note that the bike industry is only following trends throughout the world. Serviceable assemblies are being replaced with modular construction wherein a problem component isn't repaired or adjusted, but simply replaced. Look at anything, cars, computers, appliances, etc. Skilled mechanics and things that need them are going the way of the dodo bird, and being replaced with modules and module replacers.

    We call this progress.
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  3. #3
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    Finding decent cranks and bb's for square taper isn't easy. And will only get harder. It'll be around for years, but slipping towards Huffy level quality.

    I still have not changed (most of) my bikes past square tapers.

    Square tapers had their drawbacks too, but they also had an extended time in development too. ISIS, Octalink, and now outboard cranks don't have the same time frame in development. I still think those 'standards' could have provided similar levels of quality given even decent development time. But the 'standard' changes quickly enough to make my cranks 'retro'.

    And lets not forget that some of the square taper cranks and BB's were pretty bad too. There were reports of bent spindles, bearings fried, cranks that wallowed out, random creaks, etc. I wonder why when we get nostalgic, we forget the things that were a pain about the old stuff. I've seen people who still love threaded headsets too...

    Square taper has three big benefits - they spin smooth (and like you noticed free bearings spin smoother than even cartridge bearings (in general) ), that you can meddle with chainline much, much easier, and you can (or least could) piece together a pretty lightweight setup for not too much coin.

    The biggest things I'm seeing is most of the cranks are becoming industry friendly. Two sizes for the crankarms, and that's it. Much less to worry about from the manuf's point of view - we don't have to worry if our tolerances match those of another company's BB - because it's OUR BB! We don't have to worry about making different, and hard to sell, sizes of BB, since it's one size fit all. Our costs can be streamlined, because we don't have to worry about selling the BB and crank as two pieces, or six different bb sizes, or four sizes of cranks (those were the days, 170, 172, 175, etc...).

    And since we sell the cranks as a unit - we can control final retail price better. No more worries that the XT BB and the LX Crank turn out to be a better value and seller than the 'complete' XT setup. Or that our $40 crank and a $50 BB is almost as light as our top end. (See Deore Hollowtech arms, aftermarket rings, and a decent BB)

    I'm a cynic and a retro-grouch, but I want improvements to make the bike work better, not to improve the bottom line. ISIS didn't do that, Octalink didn't do that (I think they had 4 different spindles going at one point), and outboard cranks are debatable at this point, with me not holding out much hope.

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  4. #4
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    Quote Originally Posted by JmZ
    Finding decent cranks and bb's for square taper isn't easy. And will only get harder. It'll be around for years, but slipping towards Huffy level quality.
    I did do some looking around yesterday, not so much for square-taper per se, but for anything using internal rather than externalized bearings. Race Face's site didn't list anything. Shimano uses external bearings for all but their really low-end cranks.

    I did find Middleburn cranks on the Chain Reaction Cycles site. Those look interesting, and can be had in both square-taper and ISIS. Then it would be a matter of finding quality bottom-brackets of those types.

  5. #5
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    Sealed unit square taper bottom brackets are still available. I just ordered a UN-54 for my old Bianchi. The cup and cone BB just didn't want to stay adjusted anymore. I'm not sure why, but after every ride the adjustment would back off. I tried locktite, different adjustment methods, but it still came loose. It wasn't worth the headache anymore, with a sealed square taper unit available for $24 at Speedgoat. IIRC Jenson has them too, so does Tree Fort.
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  6. #6
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    I wonder if you did the crank-spin test on external ceramic BBs if they'd outspin a cheap old shimano cartridge BB (like an LP20) or an Octalink/ISIS BB setup (for an equal weight of crankarm and pedals... more weight on the outside of the arm means more momentum to keep the sucker spinning afterall). I'm betting simply having the fanciest bearings around still won't make up for the drag of the seals on the external BB units.

    As to shimano's current octalink offerings. They make them up to the Deore level still, and they're still fairly stiff and light if you get one of the hollowtech arm models. The engineering rule of thumb was always "strong, light, cheap... pick 2" until shimano came along and trickled the higher end technology and tooling down to the lower price level parts once they'd been paid off in previous years making the fancier parts. Of course that just solves the crank arm part of the equation. As pointed out above, you still need to source chainrings and a bottom bracket. Neco makes some nice sealed cartridge bearing BBs with alloy cups around the old UN-7x weight for square tape.
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  7. #7
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    Quote Originally Posted by JonathanGennick
    I did do some looking around yesterday, not so much for square-taper per se, but for anything using internal rather than externalized bearings. Race Face's site didn't list anything. Shimano uses external bearings for all but their really low-end cranks.

    I did find Middleburn cranks on the Chain Reaction Cycles site. Those look interesting, and can be had in both square-taper and ISIS. Then it would be a matter of finding quality bottom-brackets of those types.
    Two words: Phil and Wood (for square-taper cranks, anyway).
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    Lets not get too misty eye'd about square taper. It just wasn't intended to stand up to MTB use. Plenty of broken/bent spindles, wallowed out crank arms, and FLEX in 20+ years of use on mountain bikes.

    Both isis and external bearings can work very well, but have their own quirks....
    Last edited by turbodog; 04-01-2009 at 11:19 AM.

  9. #9
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    Quote Originally Posted by JonathanGennick
    So I'm rebuilding a friend's bike -- an old, Bianchi Avenue hybrid.

    Last night I cleaned and regreased his bottom-bracket bearings. First time I've ever worked on a cup-and-cone bottom-bracket.

    A good spin of his cranks now easily nets me a over a dozen revolutions of the pedals. I just got 14 revolutions without trying hard.

    By contrast, none of my newer and "better" bikes even comes close. I have three bikes with Shimano XT external-bearing bottom-brackets, and I'm not sure I even get three revolutions of the pedals when I spin their cranks. I certainly get nowhere near a dozen.

    I'm sitting here now, wondering how much of my energy is lost in spinning my XT cranks and whether it might be a good idea to go and invest in some square-taper cranks and bottom-brackets. (Not sure I can find cup-and-cone for mountain-bikes).

    I'm looking at this 10-year-old bike, and I'm thinking that perhaps the industry has gone backwards rather than forwards here.
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  10. #10
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    Quote Originally Posted by turbodog
    Lets not get too misty eye'd about square taper.
    It's probably not the square taper per se, but rather the issue of internal versus external bearings. All of my bikes with internal, bottom-bracket bearings -- whether square taper or ISIS -- have cranks that spin far more easily than my bikes with externalized bearings. The Bianchi that I just rebuilt is a particularly startling example of that. So I have to ask the question: Why can't my expensive, XT cranks spin like those on my friend's 10-year-old, cheap, Bianch Avenue? Is it really helping me to have to pedal harder? Aren't bearings supposed to make things easier, not harder?

  11. #11
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    Having repacked way too many loose-ball BB's, I have little fondness for them. IMHO, the contact seals are the source of the drag, more so than the bearings. I had a nice Chorus-equipped road bike back in the day. You could spin the crank and it would just go and go and go. Sadly, anytime I rode in the rain, I would have to repack the bastard because the super-smooth, low-fiction seals let in all kinds of crap without so much as a hey-how-ya-doin'. Eventually, I realized that the seals were only there to keep the grease from getting out. Over the years I've used WTB GG, a variety of UN**, FSA, Syncros, Truvativ, generic and SRAM BBs with varying results.

    FFWD to today. The outboard bearings in my XT cranks spin about as well as the day I got them in 2004. They are on their second frame. The bearing assemblies have been out of the bike twice, once when switching frames, and once to see if they needed any servicing. They didn't. No, they don't spin as smooth as the Chorus BB did, but at least I don't have to tear them down after every other ride. It's totally worth the ~0.1% efficiency loss in the drivetrain to not have to mess with them umpteen times a year.
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  12. #12
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    I had nothing against square tapers, either loose ball type or cartridge. Never had a problem with them except availability (this goes to 5 arm vs 4arm, and different bcds as well as bb type) as the industry moved on. I do like that I can remove my Shimano external bb type crank arms more easily and with fairly standard tools (well, except for that FC16 thing, but still easier than a puller), and bearing servicing is now something I can do unlike the cartridges (well, most of them). Can't wait for the next "standard", though...
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  13. #13
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    Quote Originally Posted by JonathanGennick
    So I'm rebuilding a friend's bike -- an old, Bianchi Avenue hybrid.

    Last night I cleaned and regreased his bottom-bracket bearings. First time I've ever worked on a cup-and-cone bottom-bracket.

    A good spin of his cranks now easily nets me a over a dozen revolutions of the pedals. I just got 14 revolutions without trying hard.

    By contrast, none of my newer and "better" bikes even comes close. I have three bikes with Shimano XT external-bearing bottom-brackets, and I'm not sure I even get three revolutions of the pedals when I spin their cranks. I certainly get nowhere near a dozen.

    I'm sitting here now, wondering how much of my energy is lost in spinning my XT cranks
    Very, very, little.

    That's the seals that are dragging. You also will notice that newly packed bearings often don't spin as freely as ones that are low on grease.

    There may be other reasons to go back to square taper, but I don't think this is one of them.
    Last edited by kapusta; 04-02-2009 at 09:24 AM.

  14. #14
    JmZ
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    Yup

    Quote Originally Posted by JonathanGennick
    I did do some looking around yesterday, not so much for square-taper per se, but for anything using internal rather than externalized bearings. Race Face's site didn't list anything. Shimano uses external bearings for all but their really low-end cranks.

    I did find Middleburn cranks on the Chain Reaction Cycles site. Those look interesting, and can be had in both square-taper and ISIS. Then it would be a matter of finding quality bottom-brackets of those types.
    It's about $$$. Phil Wood, White Ind, SKF are at the top of the chain. Then you've got some Euro brands that I'm less familiar with, then you get Interloc, SINZ, and others, and UN-5X series.

    It gets even more difficult if you need a 73mm shell.

    Middleburn is one of the last high end cranks available. I almost want to say 'the last', but then someone will show me another.

    My suggestions are to watch E-Bay. Normally RF Turbines, UN-7X, and Race Face BB's come up on a fairly regular basis (sometimes even NOS), but how long will that source last?

    Good luck,

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    a few comments of my own:

    1. i dont think the drag has any real effect. it steals power, sure, but not enough to notice.

    2. the outboard bearings allow for larger bearing balls. everybody says its good, right?

    3. the integrated crank design is noticeably more rigid. i dont know whether its the larger spindle diameter, or the fact that its connected to the drive side arm, but it is. i only weigh 155 lbs, and i was really impressed with the difference.

  16. #16
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    Last year i bought a 1992 XTR M900 crankset with a 1992 UN-91 square taper BB on ebay, it got used everyday for 7 months and there is a lot of mud sand all the time here, i even rode for at least 25 minutes with water up to the handlebars (I know this is not a good idea) so it was completely submerged. I haven't toutched it since the instalation. I just did the revolution test and got 18 full revolutions!!

  17. #17
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    I had the same "disturbing" realization....until a few days after installation when I realized that the drag was nearly gone. I chalked it up to the seals conforming to the rest of the parts and the grease in the bearing housing spreading around and distributing in an efficient manner. True....the first spin test was disturbing....but after a few hours in the saddle....the 2nd spin test was nearly identical to the older BB....only it was smoother. Soooooooo......whats my point? The difference after breaking in was negligible....I'm not saying you don't have a point....but I am saying that a break in period is necessary to reach optimal conditions after a rebuild or new installation.

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    i just upgraded this year to the hollowtech/external bottom bracket replacing a set of 93' deore lx (5 arm, 110/74) cranks and a cartridge bottom bracket. frankly, i won't ever go back. the bottom bracket is so much stiffer (flexing wise). i bent 3 bottom brackets previously on my bike and after the last one i just said screw it and rode it bent for 10 years. yeah, it spun better than the current setup, and my old road bike was even more old school with the cup and cone, but it was flexy. you might think we've gone backwards in bb design, but i think the companies have been looking to get the flex out of the design and they have certainly done that. i like the hollowtech/externall bb setup so much i am looking to get it for the road bike (and also going to a compact crank - but thats another story for another forum).

  19. #19
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    For MTB, I'd take the HTII set-up over square taper every time. If the drag bothers you, get Hope bearings - you'll wonder how you ever lived with the drag on your square taper BB.

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  20. #20
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    Quote Originally Posted by JonathanGennick
    So I'm rebuilding a friend's bike -- an old, Bianchi Avenue hybrid.

    Last night I cleaned and regreased his bottom-bracket bearings. First time I've ever worked on a cup-and-cone bottom-bracket.

    A good spin of his cranks now easily nets me a over a dozen revolutions of the pedals. I just got 14 revolutions without trying hard.

    By contrast, none of my newer and "better" bikes even comes close. I have three bikes with Shimano XT external-bearing bottom-brackets, and I'm not sure I even get three revolutions of the pedals when I spin their cranks. I certainly get nowhere near a dozen.

    I'm sitting here now, wondering how much of my energy is lost in spinning my XT cranks and whether it might be a good idea to go and invest in some square-taper cranks and bottom-brackets. (Not sure I can find cup-and-cone for mountain-bikes).

    I'm looking at this 10-year-old bike, and I'm thinking that perhaps the industry has gone backwards rather than forwards here.
    I think people are taking this "spin test" way to seriously, and not even understanding what it tells you. Who says it is even a good thing for it to spin 15 times instead of 5 times? An old bb with shot seals that has lost nearly all it's grease will often spin very freely on the stand, more so than a new one. New seals often cause more friction than shot ones, and grease (which most would agree is a good thing) slows down the bearing as well.

    This is a seriously flawed test.

    Again, I don't have an external bb vs square taper opinion, but please see this "test" for what it is.

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    Quote Originally Posted by SteveUK
    For MTB, I'd take the HTII set-up over square taper every time. If the drag bothers you, get Hope bearings - you'll wonder how you ever lived with the drag on your square taper BB.
    a common misconception

    the hollowtech is the hollow arm. the outboard bearings is the integrated crank design.
    there is such a thing as an octalinck hollowtech:
    http://www.dirtragmag.com/print/arti...=stuff_reviews

    no reason why a square taper bb wouldnt have hollowtech crank arms

    ive also seen an integrated crank (outboard bearings) which didnt have hollowtech arms - the sales rap said it was an oem lx

  22. #22
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    Quote Originally Posted by brake jack
    no reason why a square taper bb wouldnt have hollowtech crank arms
    I understand that you are pointing out that hollowtech and square taper refer to different things, and theoretically you could have square taper hollowtech arms, but I don't think that Shimano in fact ever made them.

  23. #23
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    Quote Originally Posted by brake jack
    a common misconception

    the hollowtech is the hollow arm. the outboard bearings is the integrated crank design.
    there is such a thing as an octalinck hollowtech:
    http://www.dirtragmag.com/print/arti...=stuff_reviews

    no reason why a square taper bb wouldnt have hollowtech crank arms

    ive also seen an integrated crank (outboard bearings) which didnt have hollowtech arms - the sales rap said it was an oem lx
    i miswrote and should have said hollowtech II, which only comes as the integrated spindel. yes, the hollowtech did come as the octalink

  24. #24
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    Quote Originally Posted by brake jack
    a common misconception

    the hollowtech is the hollow arm. the outboard bearings is the integrated crank design.
    there is such a thing as an octalinck hollowtech:
    http://www.dirtragmag.com/print/arti...=stuff_reviews

    no reason why a square taper bb wouldnt have hollowtech crank arms

    ive also seen an integrated crank (outboard bearings) which didnt have hollowtech arms - the sales rap said it was an oem lx
    HollowTech = hollow out arms
    HollowTech-II = external BB with 24mm hollow BB shaft.

    FC-M532 - non-series Shimano HollowTech-II cranks that are not HollowTech (ie: no hollow arms).

  25. #25
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    "a common misconception..."

    You'll note if you read my post again that I refer to the HTII (two) set-up, which uses, exclusively, outboard bearings. I've used other (Truvativ) outboard set-ups, but was referring, in this case, specifically to Shimano's HTII set-up.

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    i agree with the above replies, but: in my opinion, the most important part of the hollowtech 2 crank is the integrated spindle design. the hollow arms are just the topping.

    ive only ridden non hollow square and octalinck, and the new hollowtech 2 cranks.
    to know which is more important (the integrated spindle or the hollow arms), i'll have to try:
    1 hollowtech 1
    2 non hollow integrated spindle

    if anyone has, i would love to hear which is more important, rigidity wise.

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    To the OP, I will trade you all my square taper bbs, cranks and rings straight across for your external XTs. I have UN54, UN73, RF taperlock, Shimano LX cranks, RF cranks, White Bros cranks and various rings. Lots of sizes. PM me if you're interested.

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    Borison, I'm not going to rush to get rid of all my XT cranksets. I only posed what I feel is a logical question. Drag is not something I like to see on a bike. After all, my wheels spin freely. Why can't my cranks also spin freely?

    Tangentially related to my original post, I am finally getting my that bike with the cup-and-cone bottom-bracket put back together. What a job that's been. Next time I'm tempted to tear down and rebuild a bike for a friend, I hope someone wallops me upside the head with a crank or two.

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    I should have opened the offer to any members, so the original offer still stands. I'll trade my square taper stuff for your external stuff(RF, Truvativ, SLX, LX, XT, XTR, etc) . PM me if you're interested. Thanks

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    Quote Originally Posted by kapusta
    I understand that you are pointing out that hollowtech and square taper refer to different things, and theoretically you could have square taper hollowtech arms, but I don't think that Shimano in fact ever made them.
    IIRC, when the first Hollowtech (1) cranks came out, they offered a Deore version that came in square taper, along with octalink versions.

  31. #31
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    Quote Originally Posted by Borison
    I should have opened the offer to any members, so the original offer still stands. I'll trade my square taper stuff for your external stuff(RF, Truvativ, SLX, LX, XT, XTR, etc) . PM me if you're interested. Thanks
    Hey, I'll trade anyone two of my square tapers and bb's for one external crankset/bb.

  32. #32
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    Quote Originally Posted by turbodog
    IIRC, when the first Hollowtech (1) cranks came out, they offered a Deore version that came in square taper, along with octalink versions.
    I'm pretty sure the XT crank on my Phoenix is the hollow arm, square taper configuration.
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  33. #33
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    Quote Originally Posted by wv_bob
    I'm pretty sure the XT crank on my Phoenix is the hollow arm, square taper configuration.
    Hollowtech didn't come in square taper, first XT hollow arms was the M751 in 2000, with an octalink bb.

    PS Took that out of my memory and a look at mombat.org's shimano history page. Then I started thinking maybe my M750 was also, so googled M750 and hollowtech and got a few hits, so maybe you're right...I'll be pulling an M750 off a frame soon so I'll take a look then.
    Last edited by Bikinfoolferlife; 04-03-2009 at 01:54 PM.
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  34. #34
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    The biggest advantage, in my experience with internal vs. external bb bearings(xt cartridge type mostly), is durability, and serviceability. With the internal type, I wouldn't be able to make it through a season without having to replace it, they would start to creak and click while pedaling, and eventually develop so much side to side play that the chain would drop. Since I've been using the external type, I've gone two seasons with no issues (normal drag) and was able to service the bearings myself.

    When I pulled the seals off, the non-drive side was pretty dry and rust clored, and didn't spin too freely, but as soon as I degreased and relubed it, it was good as new. The drive side bearings looked really good for two seasons of riding in the notheast.

    The other thing I like about the newer designs is the non-interference fit. With the older square tapers and even the octalink style cranks, every time you take the crank arms on and off you are wearing down the crankarm at the interface. A fellow rider had taken his cranks on and off enough times, that he wore his crankarms out to the point that they wouldn't fit on the spindle tight.

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    Not hard at all, not at all, to find really decent square taper BB's and excellent Square Taper cranks.

    It's harder to find a decent and quite modern external BB with an OK cranks these days.
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    Quote Originally Posted by kapusta
    I think people are taking this "spin test" way to seriously, and not even understanding what it tells you. Who says it is even a good thing for it to spin 15 times instead of 5 times? An old bb with shot seals that has lost nearly all it's grease will often spin very freely on the stand, more so than a new one. New seals often cause more friction than shot ones, and grease (which most would agree is a good thing) slows down the bearing as well.

    This is a seriously flawed test.

    Again, I don't have an external bb vs square taper opinion, but please see this "test" for what it is.
    Seems like a pretty simple, logical test to me, but I am just a guy with a degree in Physics. If yo uspin one and it turns 15 times, and you spin the other and it doesnt' turn at all, chances are there is more friction, or drag as other like to say, on the one not spinning. If instead of not spinning at all and just spinning 3 times around, it's obvious there is more drag on the crank and you will have to expend more energy to turn it.

    I missing something obvious here?
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  37. #37
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    Quote Originally Posted by Justanuthabika
    The biggest advantage, in my experience with internal vs. external bb bearings(xt cartridge type mostly), is durability, and serviceability. With the internal type, I wouldn't be able to make it through a season without having to replace it, they would start to creak and click while pedaling, and eventually develop so much side to side play that the chain would drop..
    I wonder if anyone has an opinion on the crank brothers bb's. They came out with an isis bb right around the time external stuff was taking off. CB offers a 5 year waranty with these. Are they really better than anything shimano makes. Why no external bb from CB offered yet?

    Just curious cause I bought the cyan about 1.5 years back. Haven't used em yet but will be installing in the next couple of weeks.

    Edit: And with CK coming out with a external bb anyone think CB will be itching to do the same.

  38. #38
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    Quote Originally Posted by Wildeyes
    Seems like a pretty simple, logical test to me, but I am just a guy with a degree in Physics. If yo uspin one and it turns 15 times, and you spin the other and it doesnt' turn at all, chances are there is more friction, or drag as other like to say, on the one not spinning. If instead of not spinning at all and just spinning 3 times around, it's obvious there is more drag on the crank and you will have to expend more energy to turn it.

    I missing something obvious here?
    I think so. Such as, the fact that low friction =/= high durability. And that the trivial friction it takes to slow down a freely spinning crank is likely impossible to notice on a crank you are powering with your legs. And the fact that those same crank bearings may exhibit very different drag when you put load on them; one that spins freely with no load may just be very loose and lacking any viscous drag from a good thick grease, and practically lock up (or just suffer damage) under the (quite high) load a BB sees in use.

    In practical terms, there's really no difference in the energy consumed by a crank spinning freely in the stand 1 full revolution vs 10, compared to the energy a rider puts out. But there may be considerable OTHER differences between those two BB's. Sure, all else being equal, the one that spins more freely is "better". But what are the chances all else IS equal? I figure somewhere only slightly above zero. And how important are those inequalities? I figure, given that durability and safe use are among the possible considerations, they are overwhelmingly more important.

  39. #39
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    Well you have two cranks, and axel, and two sets of bearings for each crank arm. What are the inequalities you speak of? It seems you are inferring there are definite diferences, but the only difference I see between the old way and the external bearings is that the bearing are moved to the outside of the frame, bearings are more exposed to elements, and you have very limited chainline options for the externals.

    All in all it's two levers spinning on an axel held with bearings.

    I would enjoy a good story and like to hear why external bearings are all of a sudden the newest greatest standard. I have used both types of cranks for 2 race seasons, and the externals were terrible. I have gone back to internal bottom bracket. I was hoping th enew cranks with external bearing would be what everyone said they were, but they were just a big noisey hastle.
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  40. #40
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    Wildeyes- I wasn't saying the external ones are necessarily better in any way. Just that the "spin test" is a really poor criteria for picking a BB. If you compared two different in-shell BBs that way, would the one that spins longer really be the better choice? Is that just because of the friction, or are there related factors that are correlate with low friction, or is any minor friction just a tertiary concern?

    Personally I'd agree that internals are the simpler option, and seem to work just fine. As you note, externals can be noisy. That can be fixed (BB facing, super hard locktite on face) but its a hastle. The main benefit seems to be a claimed lower system weight and higher spindle stiffness / durability. Having never damaged a BB of any kind, I can't say I care to switch over. I certainly don't see BMX riders lining up for this innovation, and those are the guys who really should care about strenght vs weight when it comes to cranks and BBs, I'd think.

  41. #41
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    Quote Originally Posted by JonathanGennick
    I'm sitting here now, wondering how much of my energy is lost in spinning my XT cranks and whether it might be a good idea to go and invest in some square-taper cranks and bottom-brackets. (Not sure I can find cup-and-cone for mountain-bikes).
    Yeah, cup and cones have less bearing drag, but in reality: picture how much force goes into actually pushing your bike forward through a pedal stroke.... now picture how much resistance only your BB bearings are fighting back. The amount is so minimal, you will never notice it if it were five times that amount.

    IMO, square tapers work just fine, but external bearings are stiffer. I dunno if this translates into any real world difference in speed or efficiency. It makes a difference in feel and confidence IMO, but... meh.

  42. #42
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    Quote Originally Posted by Wildeyes
    Seems like a pretty simple, logical test to me, but I am just a guy with a degree in Physics. If yo uspin one and it turns 15 times, and you spin the other and it doesnt' turn at all, chances are there is more friction, or drag as other like to say, on the one not spinning. If instead of not spinning at all and just spinning 3 times around, it's obvious there is more drag on the crank and you will have to expend more energy to turn it.

    I missing something obvious here?
    Well, in addition to the "good" reasons for drag I mentioned (grease, seals), you also need to consider that the how the crank spins with no load on it is different than how it spins when there is a load, especially the type of twisting load you put on the bb when you crank them. That bb bearings with no almost no grease left in it and shot seals may spin great on the stand, but under load it may have more drag than a newer bearings with intact seals and lots of grease and no play.

    If anyone seriously thinks this test is a worthwhile gauge of how good your crank bearings are, then I suggest removing your seals and washing most of the grease out. Let them wear until there is just the slightest hint of play. Then they will do great on this stupid test.

  43. #43
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    Not to bring up an old thread but I threw my chain the other day so I thought I would give the cranks a nice spin. I counted 37 revolutions out of the old UN91/M900 cranks. Now I am not saying that the BB hs any grease in it but it was pretty smooth. It probably spun closer to 45 but at the beginning it was spinning too fast to count.

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