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  1. #1
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    OK, everyone now -- does BB/crank stiffness matter for SSing?

    Alright, I've searched the archives here and at roadbikereview and I still can't get a definitive answer to a question I've wondered about for, oh, two years at least.

    OK, we all know the newer splined BBs provide something like a 50% gain in stiffness over square taper, and the new external-bearing ones are stiffer yet, taking us to the point where the noodliest splined setup is stiffer than the stiffest square taper.

    So here's the big question: Does it matter - for singlespeeders? Now I really have a hard time believing it makes much difference for roadies, especially given that half the pros ride Campy, which is still square taper.

    But what about singlespeed mountain bikers? We put an awful lot more stress on that part of the bike when we're yankin' and crankin' up a steep hill at 3 mph with all the effort our poor little legs can muster. It seems reasonable to me that crank/BB stiffness at least might make a bit of a difference in getting us up that hill more efficiently, but in reality is it noticeable? And even if it "feels" noticeably stiffer, does it actually make a difference in performance or is Professor Bontrager's rant on this subject (he says the system acts like a spring, returning energy into the system as force diminishes) right on?

    Has anyone noticed a substantial difference between square taper and splined setups in terms of hill climbing ability? I'll be buying a new bike this spring and am trying to decide whether to stick with square or to get one of the new external-bearing setups (likely LX). Leaning towards square despite the weight penalty, but if the stiffness improvement was noticeable on the trail it might push me into the "new" column. Any and all replies welcome.

    - Dan

  2. #2
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    Here's the way I look at it...if the newer BBs are stiffer, I don't see how not having other chainrings or a derailleur would affect that. I suppose it boils down to does it matter to *you* and of course only you can determine that. But, I absolutely love the feel of my Saint crankset on my FR Uzzi. Solid.

    I apologize in advance if I'm being presumptuous, but it appears that you already seem to think it does, and I certainly would agree. Sure, there are other factors involved--like frame design--but I truly believe it makes a difference on _any_ bike. Again, does it matter? That's an individual determination; it may matter to one person, but not another.

    Additionally, I'm planning to build up a SS soon (my first) and I am highly considering the outboard bearing cranksets. I'd be surprised if I didn't get one. Also, if half the pros ride Campy, it is because they are paid to do so, not because they necessarily feel that one group is better or worse. But I know you knew that.

    Anyway, HTH...

  3. #3
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    Quote Originally Posted by VoltesV
    Here's the way I look at it...if the newer BBs are stiffer, I don't see how not having other chainrings or a derailleur would affect that.
    Here's how it would affect it: you ride a bike a LOT differently when you're singlespeeding. Rather than gearing down and spinning for climbs, you have to haul the bike up in a (relatively) high gear, yanking up on the handlebars and stomping down on the pedals with all your might. The amount of force exerted on the pedals on a steep singlespeed climb can easily be several times what it is for most riders doing the same climb on a granny gear. So even if it doesn't matter for roadies or geared mountain bikers, it could matter to singlespeeders. Whether or not it actually does matter is my question.

  4. #4
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    Perhaps I'm having trouble understanding your question. Maybe its semantics. Does it matter? To whom? You? Me? The distinction I'm trying to make is this... Is there a measurable difference in BB stiffness? Yes. Does it matter? Maybe to some, maybe not to others.

    Maybe a different example can illustrate my point more clearly. I know people that love semi-slicks for their lower rolling resistance at the expense of traction. Is there a difference in traction between semis and full knobbies? Yes. Does the compromise in traction matter? Not to them, but I don't like them, so to me it does.

    Although I don't own a SS, I am familiar with riding them. Personally, I think the stiffness matters since--just as you stated--you can't gear down and have to stand more. Maybe that's all you needed to hear?

    Enjoy the ride...
    Last edited by VoltesV; 01-05-2005 at 05:15 PM.

  5. #5
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    I would venture to say that most flex of the spline (from pedaling, not jumping) comes under low rpm heavy grunting which single speeders do more than our geared breatheren. From this you could say that single speeders would notice a more pronounced difference with reduced flex because they were experiencing more flex to begin with.

    However, like you said, this brings up the issue of whether the flex really matters. I mean a square spindle will have a bit of wind-up flex that will have to be released at some point which would release the energy used by the flex. This is of course ignoring energy used heat in the deformed seal, drag on the bearings from the slightly deformed spindle, etc. Honestly, it seems hard to believe that this would be a huge difference.

    I'm definitely not an expert though. I just ride .

  6. #6
    dirty hippy mountainbiker
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    Seems the less energy absorbed into the system the better. Aren't cranks built to be rigid? It's just that some are better at it than others. If we want springs why not make cranks and bottom brackets to be springs? I don't see the advantage in having some of your energy soaked up even if a portion is returned. This isn't like the slingshot bike thing where the energy is coming from somewhere else.

    A new tennis ball bounces higher because less energy is soaked up in deforming the shell. Same with cranks. Hopefully there is a geek here who can model this in his/her spare time.
    Mike Henderson, Dirty Hippy Mountain Biker and part owner of Jet Lites.

  7. #7
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    I don't think that bb stiffness is a huge contributing factor to riding. Stiffness, like light weight and carbon fiber, is a marketing tool.

    Too little stiffness is bad. Too much stiffness is bad. Square taper, splined and integrated spindles all fall withing the good range of stiffness. Even 1-piece cranks and cottered cranks are suitable. There are other, more significant things relating to the setup, such as bearing size, bb quality and bb/crank interface.
    Frank Tuesday
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  8. #8
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    Looking for real-world experiences

    With all due respect to the posts so far, I'm not looking for conjecture -- or even modeling! I've already seen the German stiffness tests, and I'm well aware of the measured differences in stiffness. As far as speculating as to whether it matters for SSing, re-read my original post and you will see that I have already done that. (And actually, let me reiterate that I'm inclined to stay square since I have yet to every hear a single person say that splined improved their SS experience -- and yet, on the other hand the question hasn't been directly asked on this board very much, so that's why I'm asking now).

    Feel free to add to the theoretical discussion if you wish, but that's not quite what I'm looking for. What I'm most interested in here is real-world experiences. I have never SSed with anything other than square taper, so that's why I'm asking. I know everyone's different and no one can speak for me, so just speak from your experience: Did it matter to you given your own personal riding style? If you switched from square to splined, could YOU feel the difference in stiffness out on the trail? Do you think it helped YOU ride faster or climb better? I'm especially interested in anyone's experience with this if they happen to have made the switch on the same bike, so that other variables are eliminated. C'mon, I know you're out there.

  9. #9
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    Quote Originally Posted by GlowBoy
    I have never SSed with anything other than square taper, so that's why I'm asking. I know everyone's different and no one can speak for me, so just speak from your experience: Did it matter to you given your own personal riding style? If you switched from square to splined, could YOU feel the difference in stiffness out on the trail? Do you think it helped YOU ride faster or climb better? I'm especially interested in anyone's experience with this if they happen to have made the switch on the same bike, so that other variables are eliminated. C'mon, I know you're out there.
    I've ridden square taper, octalink, and bmx 3 piece, sometimes trying 2 of the 3 on the same bike. I can't feel any difference between square taper and octalink. The bmx 3 piece cranks feel more solid (which I guess is stiffer). I don't believe any of them make me climb significantly better or worse. I'd put any of them on my bikes, but would go w/ the 3 piece setup all the time if there were no weight penalty. BTW, I'm 150lbs and ride xc.

    baker

  10. #10
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    Sorry, a more real-world example:

    My offroad single speed has XTR Octalink crank arms, my road fixie has a square taper Shimano Sora crank arms, and my beater has who knows what square taper 80s vintage crankset. I ride all of these bikes and often quite hard. The only one that I notice a perceptable difference is on my beater bike and honestly I attribute that to flexy crank arms.

    I cannot notice any difference between the octalink XTR cranks and the Sora cranks when used when a regular old Shimano square taper bottom bracket. Well I can, the square taper bottom bracket lasts longer . At any rate, I am not a racer but I have not noticed any pereptible difference between high quality square taper and high quality splined cranks. I would worry more about the quality of the cranks themselves than the interface.

  11. #11
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    stiffness-heh,heh...cool!

    Well, here's my $.02. I recently change to a 3-piece bmx crankset from shimano deore square taper arms. There is a definite difference in stiffness, as well as weight. I think the added stiffness might help very slightly with climbing . The biggest plus I noticed with the bmx setup, however, was that the 1 piece chainwheel is a lot better for getting even chain tension throughout the rotation of the crank. The bmx setup is noticeably heavier, also. BTW, 5'10", 180lb of rider here.
    "You know, the novelty kind of wears off after the first few times..."

  12. #12
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    I guess my post was about my experiences, though it didn't explicitly say as such. My fixie has DA splined track cranks. My other fixie has square taper ultegra. My SS has RF square taper with a XTR bb. I've used ISIS, new shimano XT. I can't tell the difference between them as far as stiffness goes. I can tell that my square taper XTR bb has lasted for 7 years now, and I go back to them after trying other setups. There is nothing wrong with the new setups, except for suspect bearing life and wider q-factors. When I believe that there is a setup that is actually better, not just newer, lighter and or stiffer, I'll make the switch. I suspect that won't be for a long time.
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  13. #13
    hispanic mechanic
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    I can feel a difference...

    I had a square taper crank/BB (Suntour XC-Pro, no cheap stuff) on the KM at first, then went to a Stylo SS crank/ ISIS BB. The only place I noticed the difference in stiffness was while coasting over rough stuff!
    I'd recommend sticking with square taper- I'll be using 'em on the Wily!

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  14. #14
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    Thanks for the feedback guys ...

    Thanks for your patience while I explained just exactly what I was looking for...

    And so far I'm not hearing any evidence of improved performance from the stiffer systems, and actually I'd meant to ask about the "ride" issue that sslos just mentioned.

    So unless someone comes along and gives a credible story of greatly improved performance from splined, I'll just put a nice dependable UN-72 in my new Vulture ... and forget about it for a few years. I should add that my KM's UN-52 in its third bike and hasn't needed any attention yet. Sorta goes along with the spirit of SSing anyway.

  15. #15
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    personally, as an SSer, BB/crank stiffness makes a big deal. since starting ssing, Ive used square taper race face setup, truvativ isis, and shin-man-o's octalink (I and II). i like the latter two and am sticking with them because I cant stand the '"noodly" feeling of a square taper system, reguardless of frame material (tried it with steel, alu and Ti).

    AS for the newest system, with the external/outboard bearings, I think it will be better, but im not sure how noticable...and upgrading all the bikes to this "new and improved" system would be costly. heck, I thought about going with the new saint DH SS crank for a while...untill i discovered the $ and the wait time turu QBP, so I ended up with the stylo 180mm isis SS cranks, which Im very happy with.

    my $0.04 new zeland doll hairs on the matter.

  16. #16
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    crank arm or BB

    When I first built up my 1x1 I went with Truvativ stylo SS because everyone else had them. I noticed alot of flex in the arms not so much the BB. I have since switched to a XT hollowteck I had laying in my bikebox and I've noticed conciderably less flex. Though I had to change the BB from ISIS Gigapipe to Shimano splined I'd have to say that the difference was very noticable and that was just cranks not so much BB.

    Also there ahs been considerably less noise on both my splined BB than on my old square taper.
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