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  1. #1
    pvd
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    BB86 is 30% stronger than BB30

    Simple leverage. Why would anyone choose BB30? Really?

    BB86 is 30% stronger than BB30 | Peter Verdone Designs

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    for the potentially narrower chainline and Q-factor. The latter was one of the reasons C-dale gave when they introduced it.
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    Offset to some extent by more balls in the bearings and a larger axle. But I've got better things to do than crunch those numbers.

    The increased friction in a BB30 is quite noticable in a new unit too.
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    more bad math by peter, too bad. you would only be correct assuming the material, wall thickness, heat treatment were the same.

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    Quote Originally Posted by bikeindustrydude View Post
    more bad math by peter, too bad. you would only be correct assuming the material, wall thickness, heat treatment were the same.
    I beleive Peter was working on bearing strength (as the drawings show) as in bearing loads will be 30% higher in a BB30 than a BB86. In this case bearing materials and heat-treatment have little variance. The ball count is likely different but I haven't stripped a 6806 to count.
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  6. #6
    pvd
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    Quote Originally Posted by shiggy View Post
    for the potentially narrower chainline and Q-factor.
    BB30 does nothing to change chainline or Q. How would that be possible?

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    The BB shell, bearings and crank axil are the last things that will flex under peddling load. The peddle spindles and crank arms will be more flexy than all above combined, to say the least. Just push down on your peddle with your foot and see where the bike flex is. Hint, not in the BB shell or crank spindle.

    How are some manufacturers saying that a BB30 is 38% stiffer than the typical 68/73? I'm confused with this one, unless their BB shell is made of plastic.

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    There will always be something stronger. That's great news for marketing guys. The question is, does it matter? You have to decide what is strong enough, and make parts that are strong enough. After that, you are done.

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    pvd
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    Another point to note here is the angle of the loads going through the bearing itself. The bearing will function far better the more the load is transferred perpendicular to the axis of rotation resulting in less fractional loss. I'll compare that later today, but its pretty obvious which system is better there. BB30 even goes so far as to specify very high angular bearings for use. Pretty lame.

  10. #10
    pvd
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    I also need to get some data on the PF30 bearings as they are smaller than BB30 the will produce a more compromised system.

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    Quote Originally Posted by pvd View Post
    BB30 does nothing to change chainline or Q. How would that be possible?
    A 68mm width shell vs an 86mm.

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    Quote Originally Posted by pvd View Post
    I also need to get some data on the PF30 bearings as they are smaller than BB30 the will produce a more compromised system.

    I thought they were the same bearings, but the bearings rest in a cup, so that the bottom bracket shell diameter goes up from 42mm to 46mm?

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    Quote Originally Posted by pvd View Post
    I also need to get some data on the PF30 bearings as they are smaller than BB30 the will produce a more compromised system.
    Pete, it's the exact same bearing dropped into a delrin cup.
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    Quote Originally Posted by Dougal View Post
    Offset to some extent by more balls in the bearings and a larger axle.
    Yeah, how do you make a claim like that without even factoring in the 24mm dia axle of the BB86 vs the 30mm of the BB 30??

    But I've got better things to do than crunch those numbers.
    Right, but Peter should do more crunching before making these bold proclamations.

    Its getting kind of funny.

  15. #15
    pvd
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    Quote Originally Posted by smilinsteve View Post
    A 68mm width shell vs an 86mm.

    Steve, just so you know pedal offset is limited by the front derailure and chainstay and crank thickness. The front derailure is limited by the chainrings. The chainrings are limited by the orientation of the chain line relating to the rear cassette. None of these factors are changed by the width of the BB or diameter of the axle. Again, just so you know.

  16. #16
    pvd
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    Quote Originally Posted by smilinsteve View Post
    I thought they were the same bearings, but the bearings rest in a cup, so that the bottom bracket shell diameter goes up from 42mm to 46mm?
    Hey there steve. You may have missed the memo that the other framebuilders got but PF30 and BB30 have the same BB dimentions other than the snap ring. It's too bad they didn't tell you.

  17. #17
    pvd
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    Quote Originally Posted by smudge View Post
    Pete, it's the exact same bearing dropped into a delrin cup.
    Sean, it can't be. The cup takes up a mm or two of diameter. The bore is the same on both PF30 and BB30.

  18. #18
    pvd
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    Just so folks know, the more balls in a bearing assembly, the more friction on the system. High end skate bearings use six instead of seven bearings in a 608 cartridge so that top speed will be faster. The increased number of bearings in the BB30 system will only produce much more drag than the BB86 system. That is combined on top of the increased angle of contact on BB30. Not cool.

  19. #19
    pvd
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    Just did the math on the working angle of the bearings.

    BB86 - 69.5 degrees
    BB30 - 57.7 degrees

    A difference of 11.8 degrees. That's substantial.

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    Quote Originally Posted by pvd View Post
    Hey there steve. You may have missed the memo that the other framebuilders got but PF30 and BB30 have the same BB dimentions other than the snap ring. It's too bad they didn't tell you.

    What do you call that attitude? Snobby? Sarcastic? Or just plain wrong?

    Now start reading:
    http://www.qbp.com/diagrams/TechInfo...bbfitchart.pdf

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    Quote Originally Posted by pvd View Post
    Just so folks know, the more balls in a bearing assembly, the more friction on the system. High end skate bearings use six instead of seven bearings in a 608 cartridge so that top speed will be faster. The increased number of bearings in the BB30 system will only produce much more drag than the BB86 system. That is combined on top of the increased angle of contact on BB30. Not cool.

    Hey its your thread, which started off by saying that BB86 is 30% stronger. Very precise proclamation, but didn't take into account the spindle diameters. Now you are talking about drag. That is a diversion.

  22. #22
    pvd
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    Quote Originally Posted by smilinsteve View Post
    What do you call that attitude? Snobby? Sarcastic? Or just plain wrong?
    Sonofa*****. I was wrong there. I was thinking back to a conversation with SRAM that the point of PF30 was to be backwards compatable. I guess things changed since they released it. Yes, 46mm bore vs 42mm bore. Still a stupid design but PF30 is slightly less stupid.

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    Quote Originally Posted by pvd View Post
    Sonofa*****. I was wrong there. I was thinking back to a conversation with SRAM that the point of PF30 was to be backwards compatable. I guess things changed since they released it. Yes, 46mm bore vs 42mm bore. Still a stupid design but PF30 is slightly less stupid.

  24. #24
    pvd
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    Quote Originally Posted by smilinsteve View Post
    Hey its your thread, which started off by saying that BB86 is 30% stronger. Very precise proclamation, but didn't take into account the spindle diameters. Now you are talking about drag. That is a diversion.
    Nothing of the kind. I'm talking about bottom bracket design and you are talking about crank design. It's a shame that I keep bringing real data, measurements, and summation to the table and you aren't bringing anything. Why don't you produce something and show it? Are you just a critic? I'm a critic too but I'm producing value with it and adding to the discussion. Are you just jabbing and not adding? That's easy.

    BB30 was invented so that manufactures could replace hollow steel spindles with hollow aluminum spindles and have them end up ligher with some sort of margin of safety and cheaper production. The proble is that the design produces a heavier frame, more drag on the bearings, higher bearing loads, and it makes no sence. Sure a mass manufacturer (Cannondale) can save a bunch of money when processing frames on a CNC machine but it doesn't elevate frame design at all. In the end, a consumer can point to a crank that weights 10g less than another to feel good but ignoring all the drawbacks.

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    Quote Originally Posted by pvd View Post
    Nothing of the kind. I'm talking about bottom bracket design and you are talking about crank design. It's a shame that I keep bringing real data, measurements, and summation to the table and you aren't bringing anything. Why don't you produce something and show it? Are you just a critic? I'm a critic too but I'm producing value with it and adding to the discussion. Are you just jabbing and not adding? That's easy.
    I'm not jabbing without adding. I brought up the point that your calculation neglected to consider spindle diameter. You say there is higher load on the bearing, and I'm saying the load is distributed over a larger area.

    BB30 was invented so that manufactures could replace hollow steel spindles with hollow aluminum spindles and have them end up ligher with some sort of margin of safety and cheaper production. The proble is that the design produces a heavier frame, more drag on the bearings, higher bearing loads, and it makes no sence. Sure a mass manufacturer (Cannondale) can save a bunch of money when processing frames on a CNC machine but it doesn't elevate frame design at all. In the end, a consumer can point to a crank that weights 10g less than another to feel good but ignoring all the drawbacks.
    The SRAM example above showed the BB30 to be 150g lighter than the X type BB. Not 10g. I have to admit, I'm having trouble believing it myself.

  26. #26
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    Quote Originally Posted by pvd View Post
    Sean, it can't be. The cup takes up a mm or two of diameter. The bore is the same on both PF30 and BB30.
    This is not correct. The BB30 shell ID is ~42mm. The PF30 bore is ~46mm.
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    Quote Originally Posted by DWF View Post
    This is not correct. The BB30 shell ID is ~42mm. The PF30 bore is ~46mm.
    Why can't they just make a BB that reams to 44mm so my headtube reamer will work in it? at 42 and 46 they have it surrounded.

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    Hey Pete,

    This is all in good fun, but I think you're missing what this all means to the consumer. Ultimately, it doesn't mean much.

    I would appear that you're looking at leverage points on a bearing. What does "stronger" mean to you in that context? How does it relate to axle material; diameter; crank system? What are the associated real-world impacts from a system that's uh...not "stronger". How important is "stronger" when the bearings have to be replaced "regularly" in **** conditions?

    Most importantly, how is your view of "stronger" different than any of the other marketing ******** that's tossed at consumers from manufacturers.

    BTW - I'm of the "if it works for you, ride it" opinion. I love Shimano cranks and I love them more now that King makes BB's that fit them. I love them because, for the most part, they've never let me down (though I have a partially crushed 950 BB spindle in my parts bin). I also love my Cannondale cranks because I can tweak the spider and make it work with my goofy drivetrain. I like options. Being able to change spiders gives them to me. I like to dick around with stuff and to be perfectly honest...I have yet to find a downside to the PF30 platform and my Cannondale cranks.

    P.S. does 30% stronger matter if no one can tell the f'ing difference?

    edit: aww crap...are you just doing this to get blog views? I'm a sucker...that may or may not be interested in arguing.
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    Total crap. A BB30 shell made frame steel is going to be stronger than a BB86 made of aluminium. Heavier as well. We don't ride BB shells, we ride the whole bike, and stiffness is more related to tubing size and material than the diameter of the BB shell.

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    I know! I know!

    Quote Originally Posted by smilinsteve View Post
    what do you call that attitude? Snobby? Sarcastic? Or just plain wrong?

    Now start reading:
    http://www.qbp.com/diagrams/techinfo...bbfitchart.pdf
    the answer is c, "just plain wrong."
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    I know! I know!

    Quote Originally Posted by DWF View Post
    This is not correct. The BB30 shell ID is ~42mm. The PF30 bore is ~46mm.
    The answer is, "PVD is plain wrong." AGAIN!
    "I can only assume chan slap is what happens when you get assaulted by Jackie Chan. I don't think anybody can prevent that."

  32. #32
    pvd
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    @thesenator.

    Thank you very much for pointing out the one mistake that I carelessly made and that has been explained and discussed. It is a constant problem for me, as one that creates a great deal of data and explains engineering and design for others not to mention produces real artifact, that from time to time a simple misspelled word or exact specification may slip through in all of the material I produce. I do my best, but sometimes I use poor grammar. It's a problem.

    Btw, It seems that you have posted on an anonyms profile. I was hoping to review some of YOUR work to get an idea of how I should be doing things. It sounds like you really know what you are talking about and I wanted to see some links to your work and some scientific explanations as to why you made your decisions. Please get back to me ASAP. I can't afford to make any more mistakes ever ever again.

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    Please, can we stay on topic?

    Quote Originally Posted by pvd View Post
    @thesenator.

    Thank you very much for pointing out the one mistake that I carelessly made and that has been explained and discussed. It is a constant problem for me, as one that creates a great deal of data and explains engineering and design for others not to mention produces real artifact, that from time to time a simple misspelled word or exact specification may slip through in all of the material I produce. I do my best, but sometimes I use poor grammar. It's a problem.

    Btw, It seems that you have posted on an anonyms profile. I was hoping to review some of YOUR work to get an idea of how I should be doing things. It sounds like you really know what you are talking about and I wanted to see some links to your work and some scientific explanations as to why you made your decisions. Please get back to me ASAP. I can't afford to make any more mistakes ever ever again.
    One mistake? You made TWO mistakes. Unless of course we count you saying that you made only one mistake (instead of two) as a mistake, then you made THREE!

    You were wrong, and then corrected, and still insisted you were right. Then, in your very same thread, did it again. Bravo! Grammer? I didn't say anything about grammer???

    I would not fault anyone for making a mistake. Ever. Although, it is quite different when someone pretends to be an authority on a subject, and then when they are corrected twice in their own thread, to stll insist they are correct before rechecking the facts.
    "I can only assume chan slap is what happens when you get assaulted by Jackie Chan. I don't think anybody can prevent that."

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    In light of the arguments in this thread PVD, I think you need to provide more support for your assertion.

    BB 30 has a bigger diameter axle which means it will flex less

    BB 30 bearings are closer together, which may put more stress on the bearings, but provides more support for the axle, again resulting in less flex.

    BB30 stress on the bearings is distributed over a larger area (more bearings) than BB 86.

    In light of all this, do you still stick by your original claim?

    BB86 is 30% stronger than BB30

  35. #35
    pvd
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    Quote Originally Posted by thesenator View Post
    One mistake? You made TWO mistakes. Unless of course we count you saying that you made only one mistake (instead of two) as a mistake, then you made THREE!

    You were wrong, and then corrected, and still insisted you were right. Then, in your very same thread, did it again. Bravo! Grammer? I didn't say anything about grammer???

    I would not fault anyone for making a mistake. Ever. Although, it is quite different when someone pretends to be an authority on a subject, and then when they are corrected twice in their own thread, to stll insist they are correct before rechecking the facts.
    Wow. Seriously. Wow.

  36. #36
    pvd
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    Quote Originally Posted by smilinsteve View Post
    In light of the arguments in this thread PVD, I think you need to provide more support for your assertion.

    BB 30 has a bigger diameter axle which means it will flex less

    BB 30 bearings are closer together, which may put more stress on the bearings, but provides more support for the axle, again resulting in less flex.

    BB30 stress on the bearings is distributed over a larger area (more bearings) than BB 86.

    In light of all this, do you still stick by your original claim?
    Steve, I have not seen any calculation showing that the axle is stiffer. It is larger in diameter, but that means nothing without math. I'm willing to bet that the steel axle is just as stiff, but a cyclist isn't going to twist or bend either really. Can you show me that this is true? The surface area at the bearing and axle may go up too, but does this change anything regarding the strength or stiffness of the system? I don't see that this is the case. Certainly with the higher bearing count and larger angle of contact fractional losses in the system are far greater. 11 degrees of difference is massive.

    Still mine is the only calculation of any kind that I've seen on these systems. That being the case, I will bet on it being right until I see some kind of math from anybody else.

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    A good precedent

    right or wrong, I think PVD is setting a good precedent -- one of doing the math and testing out the overarching/sweeping claims of manufacturers. When someone says that their new thing is inherently stiffer/better/lighter than what another company or another design provides, I would love to see how they came up with that claim. Just saying it's stiffer because it's a larger diameter axle is not true. It could be a thinner wall, etc. Unfortunately, I rely on others to do the math since I'm not an engineer, but I would love to see something like what happens in every other scientific discipline = peer reviewed published papers supporting their claims along with references and the whole 9 yards. It's stiffer? Prove it.

    But the biggest question to me is: even if these things are stiffer, will anyone even notice? Doing a "blind" ride-test, do you think the majority of riders would notice the difference between a square taper BB and a BB30...? (All other things held constant?) I'm just not so sure.

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    Quote Originally Posted by pvd View Post
    Steve, I have not seen any calculation showing that the axle is stiffer. It is larger in diameter, but that means nothing without math. I'm willing to bet that the steel axle is just as stiff, but a cyclist isn't going to twist or bend either really. Can you show me that this is true?
    Hey Pete, isn't this a major copout? Would you be satisfied if someone else put up a very simple drawing, made a pretty grandiose claim and then argued that claim holds up until someone else proves it wrong? "willing to bet" doesn't sound like a PVDism to me.

    Quote Originally Posted by pvd View Post
    The surface area at the bearing and axle may go up too, but does this change anything regarding the strength or stiffness of the system? I don't see that this is the case. Certainly with the higher bearing count and larger angle of contact fractional losses in the system are far greater. 11 degrees of difference is massive.
    Again, you provided an elementary drawing and conclusion based on one part of the system...I don't actually see any argument on the entire system. You'd have to account for crank arm twist, BB axle length, arm attachment point, bearing location, bearing size, axle stiffness...ultimately I don't think you (or anyone) can actually use math because the dataset is either incomplete or simply unavailable to most people. If you're really gung ho about this (and I assume you are since you've brought this up quite a few times) why not use your seemingly significant resources and make a test rig that tests crank stiffness at the axle - which is the only significant-to-consumer way to do it IMO
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    Quote Originally Posted by smudge View Post
    why not use your seemingly significant resources and make a test rig that tests crank stiffness at the axle - which is the only significant-to-consumer way to do it IMO
    This is exactly what industry engineers do while creating these types of standards. Just because the marketing folks are the ones presenting new products to the public does not mean those products were not based on sound engineering and testing.

    I don't know how many people here have been in the test labs for companies like C-dale or Spec, or run a servo hydraulic fatigue machine to test the BB stiffness of a frame, but there is a lot of testing done in this industry. I'm not saying that every new development is a good for all riders. Everyone in this forum should know that bike design is all about compromise. The engineers who came up with the BB30 had to compromise some attributes of the system in order to accentuate others. This balance doesn't seem to work for PVD, but to make an overarching claim about a system based on one characteristic is about as accurate as the way the aforementioned marketing folks present products to public.

    In my conversations with someone who was involved with the development of the BB30, I understood that they were trying to both improve the BB shell stiffness as well as the crank/axle interface. They were quite happy with the results of the complete system when tested in the lab as well as on the road. Personally, I'm happy with the threaded BB and I've never owned or ridden a BB30 so I can't comment to the ride or durability.

    Of course you still need to think through the claims of every manufacturer as they do tend to exaggerate when writing the copy for their products. I just get a little worked up when people talk as if all the bike industry is doing is hyping useless products. There are a lot of passionate people involved in the product development and some of them even have some good ideas every once in a while.

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    That, in a roundabout way, was my point.

    There's so much marketing drivel out there and as a result, there are some consumers who are constantly chasing their tail (and spending $$ to do so, WIN for the bike industry eh?) trying to figure out what's best. I don't assume it doesn't exist, but I haven't seen a comparative study done on cranks and more importantly, what the extra stiffness actually means from a performance standpoint. I'm not convinced that stiffer is actually better.

    So here we have Pete, who has some credibility essentially making a headline without presenting a good argument let alone a complete dataset with any meaningful information and it feels like hype. I assume that most of the contributors to this board and a good number of consumers roll their eyes and pass it off as a Peteism but others won't...they'll see that he "uses math" and provides a couple of pro looking drawings and will completely buy it. And well...I guess I don't get it. What's the point? Is Pete trying to draw views to his site? Does he have connections to Shimano and is he doing his version of guerrilla marketing for them?

    I'll write this again in case it was missed earlier...I LOVE Shimano cranks, they're fantastic. But there's a lot of other great stuff out there too.
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  41. #41
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    Quote Originally Posted by whydomylegshurt? View Post
    In my conversations with someone who was involved with the development of the BB30, I understood that they were trying to both improve the BB shell stiffness as well as the crank/axle interface.
    Is BB shell stiffness really an issue?
    Has anyone ever felt the difference in BB shell stiffness?

    Has anyone ever had a BB shell break as a result of it not being stiff enough?

    I can understand the drive to improve the robustness of the drivetrain, but what's really the concern with BB shell stiffness?

    After my experience with my Specialized Roubaix S-Works and its BB30, I'm a little tainted. Sure, that was a simple manufacturing problem (bearing bore slightly too big, causing the bearing to move and creak) not a BB30 conceptual problem. I just see how it's another possibility of something going bad in production.
    May the air be filled with tires!

  42. #42
    pvd
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    @ Sean,

    This is a forum. We talk about things. I presented an argument using math and geometry. I show that the bearing structure, which I consider very important on a bicycle, is weaker in terms of loading (by 30%) and produces more friction in terms of angle of load (by almost 12 degrees in the bearing) on BB30 compared to BB86. It's NOBODY has corrected any of my math there. People have mentioned other parts of the crank system, but they have all failed to produce any math or numbers or testing data to support their claims.

    I did make a bold statement. I'm happy to look at REAL MATH or DATA that shows that I am wrong or that I am off track but all I have seen is conjecture and marketing hype. I have not prevented anyone from pulling out a calculator and checking my work. I INVITE them to. Remember, I did real work to show what I have shown (actually, not much but something). Others have only brought argument based on pure assumption.

    Also, I really have no reason to need to boost traffic to my site. I have a habit of putting my work on a web page as I learned long long ago that message boards are no place to reposit information. Typicially I develop a page with a fully elaborated argument to support my cases. In this case I haven't had the time or energy to fully develope this page as much as I'd like.

  43. #43
    pvd
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    Quote Originally Posted by whydomylegshurt? View Post
    I don't know how many people here have been in the test labs for companies like C-dale or Spec, or run a servo hydraulic fatigue machine to test the BB stiffness of a frame, but there is a lot of testing done in this industry.
    I've visited and worked in many environments that you mention in the bicycle, motorcycle, and general industry. This past July I was given a full tour of Time Bicycle (yes, France). Engineering, testing, and production. Very nice.

  44. #44
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    Quote Originally Posted by Meriwether View Post
    But the biggest question to me is: even if these things are stiffer, will anyone even notice? Doing a "blind" ride-test, do you think the majority of riders would notice the difference between a square taper BB and a BB30...? (All other things held constant?) I'm just not so sure.
    From square taper, certainly. But from ISIS onwards I doubt it.
    I've recently migrated from ISIS to GXP. I can't tell the difference stiffness-wise when riding. Going from Square Taper to ISIS way back in 2003 I felt a big difference.
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    Hi

    ok let me reply on that. I just made some simple drawings and feed ANSYS with them. Both are the same outer diameter and (48mm), the diameter for the bearings refer to the standard (41,96mm for BB30 and 41mm for BB86). Axel length is 150mm for both.

    The first test was a fixed support at the one side of the axel and on the other side I add a movement of 1 mm for both BBīs. So in theory the one resulting in a higher stress should be the stiffer one.
    The second run was adding a Seattube with about 300mm length and moving the fixed support from the one side of the axle to the top surface of the tube.

    If somebody wants to make som changes please post a drawing of the BB and Axle specs. As I didnīt had them when drawing it was mor guessing...

    results:
    1. BB30
    2. BB86
    3. BB30 with seat tube
    4. BB86 wih seat tube
    Attached Thumbnails Attached Thumbnails BB86 is 30% stronger than BB30-bb86.jpg  

    BB86 is 30% stronger than BB30-bb30.jpg  

    BB86 is 30% stronger than BB30-bb30_seattube.jpg  

    BB86 is 30% stronger than BB30-bb86_seattube.jpg  


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    Ahh sorry made a mistake the relevant picture for the BB30 with seat tube is this one. Hope that are enough numbers and facts to discuss
    Attached Thumbnails Attached Thumbnails BB86 is 30% stronger than BB30-bb30_seattube.jpg  


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    I would think that the seat tube test should be done as a whole frame as I can see were the down tube and chain stays would give it some support. And how about comparing it to a threaded eruo 68/73 BB for a base line.

    Tim

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    Quote Originally Posted by TimT View Post
    I would think that the seat tube test should be done as a whole frame as I can see were the down tube and chain stays would give it some support. And how about comparing it to a threaded eruo 68/73 BB for a base line.

    Tim
    Would nice to know. you are right. Maybe I will draw a Frame and feed ansys with that. but right now my time is limited and I can use ANSYS only at work. Maybe I will give it a try and tes Autodesk Multi Physics at home. but ANSYS is a little better sofware; Ithink.

    If somebody has CAD drawing of a whole frame I can run it through the program otherwise you have to wait. (I can handle Inventor, Solid Works files and step files) to the seat tub I think its OK to show the main point. You are rigth you should do it with the whole frame but just to compare two standards its OK when having the same setup in the environment.

    But as I said if somebody has a frame (or other CAD modles) he want to get analysed send me a message.

    Felix

  49. #49
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    @Felix,

    That's awesome. Thanks for bringing that to the table.

    From what I'm seeing, Neither shell is really different from the other, which I figured. BB shells aren't the most flexible tube on the frame.

    Also, it's clear that the seat tube is flexing far before anything happens to the BB. This is clear enough.

    Basically, BB shell flex is not an issue.

  50. #50
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    Quote Originally Posted by pvd View Post
    @Felix,

    That's awesome. Thanks for bringing that to the table.

    From what I'm seeing, Neither shell is really different from the other, which I figured. BB shells aren't the most flexible tube on the frame.

    Also, it's clear that the seat tube is flexing far before anything happens to the BB. This is clear enough.

    Basically, BB shell flex is not an issue.
    yeah, I think its clear. even if the BB30 BB get about double the stiffnes then a BB86 BB but in the end its just 0.4MPa what is about 0.05% of the strength of 4130.

    but anyway can somebody explain to me how this forim is working or why I donīt always see the newest post at the end? That confuse me all the time...

    Felix

    But still looking for a 3D frame to analyse it if possible with all the standar butting to maybe get a feeling about thickness and diameter compared to rider wight

  51. #51
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    Before we get all crazy in the analysis, maybe we should clarify what "stronger" means?

  52. #52
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    Quote Originally Posted by dr.welby View Post
    maybe we should clarify what "stronger" means?
    An improvement on the durability and efficiency of the defined system. My focus here is the function of the rotation and the support of that system.

  53. #53
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    Quote Originally Posted by felixv View Post

    but anyway can somebody explain to me how this forim is working or why I donīt always see the newest post at the end? That confuse me all the time...

    Felix


    At the upper right hand corner of the page there is a drop down box that say's "Display Modes", click on that and select "Linear Mode".

  54. #54
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    You guys are trying to isolate one variable but you have to consider the bike as a whole. The tubes twist too, esp the DT when pedaling. Want to stiffen up the structure beef up the DT & CS's.

    The "Industry" likes to get people to concentrate on one allegedly digestable thing which goes awry like shorter is better CS's for everything, or stiffer is better for everything. how stiff do you want a bike to be? Some flex is good! - Steve Garro, Coconino Cycles.
    steve garro el jefe/el solo. coconino cycles www.coconinocycles.com www.coconinocycles.blogspot.com

  55. #55
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    Quote Originally Posted by AZ.MTNS View Post
    At the upper right hand corner of the page there is a drop down box that say's "Display Modes", click on that and select "Linear Mode".
    my hero, Thank YOU.

    I'm german native so I really wasn't looking up there

    What does "stronger" means? In my opinion as an engineer its a system what is resisting a higher stress, what cause a higher durability and longer lifetime...
    Anyway I didn't want to analyze a bike frame. It was just my part to the "30% stiffer".

    But as i said: give me a CAD model of a frame and I'm going to analyze it. I even would analyze it on your specs...
    Ok if I find some time to make some drawings I will post the results as I know constructing a bike frame is a pain in the ass and close to no one is going to do it if its just about a geometry.

    Felix

  56. #56
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    Quote Originally Posted by pvd View Post
    Another point to note here is the angle of the loads going through the bearing itself. The bearing will function far better the more the load is transferred perpendicular to the axis of rotation resulting in less fractional loss. I'll compare that later today, but its pretty obvious which system is better there. BB30 even goes so far as to specify very high angular bearings for use. Pretty lame.
    Can you please explain what you are talking about here? From what I can tell, the bearings used for both systems are deep groove type:

    http://www.bb30standard.com/tech_ima...30standard.pdf

    And wouldn't rotation around a smaller diameter shell result in more friction?

    And as far as strength, the BB 30 bearings (6806)have a higher load rating than the 6805:

    Basic load ratings(Lbf) Weight

    6805 (25 37 7)

    Dynamic(Cr) = 967
    Static(Cor) =663


    6806 (30 42 7)


    Dynamic(Cr) = 1057
    Static(Cor) =821

    Bearing Works :: Bearing Sizes

  57. #57
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    @Steve,

    Now that's what I'm talking about!!! OK. I was waiting for someone to argue the load rating of the bearings using cited data. The thin is that the difference is only 8.5%. It does show that the bearings are capable of a larger load, but not enough to make up for the 30% leverage difference working against them.

    Also, remember that these bearings are working with a tilting moment.

  58. #58
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    I have a simple CAD model of a HT frame. It's not accurate regarding tube size or thickness to any real bike, but it's a good starting point. No problem to send you an IGES file or similar.
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  59. #59
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    Here's a good one:

    SMB Bearing Load Rating

    "Axial load rating
    Thin-section deep groove ball bearings can support axial loads of approximately 25 percent of the bearing's static radial load rating. Larger series such as 6200, 6300 can take axial loads of about 50 percent of the static radial load rating. To exceed the recommended limits will have a detrimental effect on bearing life."

    Given that the BB86 bearings are working at 69.5 degrees when working in a tilting moment, 35% of the load will be axial. The BB30 at 57.7 will be loading 53% axial. Gralnted we may not see the maximum load ratings of these bearings, but we do know that if that happens, the BB30 will exceed 50% in the axial. Not good, especially given that the higher loads will be seen on that system.

  60. #60
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    I don't see the large side loading in these Peter. Draw a FBD, it's a simple cantilever arrangement.

    The main forces are applied and resolved vertically front the pedals and roughly horizontally from the chain. Side loading is only secondary from these forces not being exactly vertical or horizontal.
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  61. #61
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    Quote Originally Posted by pvd View Post
    Here's a good one:

    SMB Bearing Load Rating

    "Axial load rating
    Thin-section deep groove ball bearings can support axial loads of approximately 25 percent of the bearing's static radial load rating. Larger series such as 6200, 6300 can take axial loads of about 50 percent of the static radial load rating. To exceed the recommended limits will have a detrimental effect on bearing life."

    Given that the BB86 bearings are working at 69.5 degrees when working in a tilting moment, 35% of the load will be axial. The BB30 at 57.7 will be loading 53% axial. Gralnted we may not see the maximum load ratings of these bearings, but we do know that if that happens, the BB30 will exceed 50% in the axial. Not good, especially given that the higher loads will be seen on that system.
    Where are you getting these angles from?

  62. #62
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    Take a look at my initial drawing. You will see the angle that the load take through the bearing.

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    Quote Originally Posted by pvd View Post
    Take a look at my initial drawing. You will see the angle that the load take through the bearing.
    Yes I saw that drawing in the original posts. But I don't agree with the load angles you are taking from that.

    To get loads at those angles would require a loose fit axle pivoting around the centre of the drawn circle. But that's a long way from the real situation. The real situation is a cantilever, pivoting off one bearing and the resulting moment resisted by the other bearing. The prime consideration with this is seperation between the bearings.
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  64. #64
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    I'm not a mechanical engineer, but I don't understand the angles either.

    Actually, I don't understand the point of the thread. I'd think either BB is plenty strong or stiff enough in and of itself. The point of both BBs is to have more realestate to lay up more carbon fiber around the BB area instead of being limited with external bearing cups.

    Also, isn't BB30 proprietary to Cannondale? So, BB86 probably wasn't designed to be stronger, but just a way to get around a patent. Having both in the market, you can get a Cannondale, or some other brand using internal BB bearings, and have a frame built up around the BB to be stiff there. Personally, if I was bike shopping, I wouldn't be concerned with which internal BB bearing system a bike had, as long as it had internal instead of the external cup style. :shrug:

    EDIT- Oh, for a new bike, I'd also gravitate towards the one with a smaller q-factor. I'm not really liking the wide q-factor of my XT crankset using external bb cups.
    Have fun!

  65. #65
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    Quote Originally Posted by pvd View Post
    Just did the math on the working angle of the bearings.

    BB86 - 69.5 degrees
    BB30 - 57.7 degrees

    A difference of 11.8 degrees. That's substantial.
    Is "working angle" the right term? I can't find anything in Google when I search for that phrase.

    And let's say you made the BB30 bearing 30% smaller than the BB86. Then you'd have the same "working angle". But I think we'd all say that the BB 86, with a comparatively larger bearing and wider spacing than our hypothetical miniBB30 would be superior. So what does "working angle" tell us?

  66. #66
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    Quote Originally Posted by Wheelspeed View Post
    I'm not a mechanical engineer, but I don't understand the angles either.

    Actually, I don't understand the point of the thread. I'd think either BB is plenty strong or stiff enough in and of itself. The point of both BBs is to have more realestate to lay up more carbon fiber around the BB area instead of being limited with external bearing cups.

    Also, isn't BB30 proprietary to Cannondale? So, BB86 probably wasn't designed to be stronger, but just a way to get around a patent. Having both in the market, you can get a Cannondale, or some other brand using internal BB bearings, and have a frame built up around the BB to be stiff there. Personally, if I was bike shopping, I wouldn't be concerned with which internal BB bearing system a bike had, as long as it had internal instead of the external cup style. :shrug:

    EDIT- Oh, for a new bike, I'd also gravitate towards the one with a smaller q-factor. I'm not really liking the wide q-factor of my XT crankset using external bb cups.
    BB30 is open source and is free to use by anybody. Originally designed by C'dale for road frames and to be stiffer than standard internal splined BBs. Can keep a narrow Q-factor.

    BB86/92 is the direct frame fit bearing version of Shimano's external bearing crank/BB.
    Last edited by shiggy; 08-25-2011 at 09:23 PM.
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    see the deal here Peter is that nobody believes you because you were so insistent when obviously wrong. sure, it was a small thing to make a mistake on, but you insisted three times that you were right, when you were not. leaves us wondering what other crap you are screwing up too.

    you made the claim that BB86 was stronger than BB30. you didnt say from the start that you meant the bearing spacing was stiffer, blah, blah. You made a statement about the whole system, which you need to take into account all the peices, such as the bb86 spacing has to be better in order to make up for the flexier spindle. in the end, both systems are probably similar in overall.

    and you got a TOUR of TIME! holy bees knees, we better start worshipping you.

  68. #68
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    @ bikeindustrydude.

    Who are you? Not many people here feel the need to remain anonomys. You toss out a bunch of conjecture with no real data or math. At least back up your lame drivel by showing what you've done and how you got there.

    BTW, there is a kid at my local bike shop. Not the smartest kid. He sweeps the floor. He's a bike industry dude too. Kinda like you?

  69. #69
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    @Wheelspeed

    BB30 does not produce a different 'Q-factor' than any other system. That is marketing lies.

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    Hey PVD, you would be smart to let this thread die. Attacking posters here isn't going to change the fact that your "analysis" is a joke.

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    I don't see the term "working angle" in either document. Is this a bearing specification you looked up or is it derived from the angle relative to the axle centerline of the line tangent to the circles you drew?

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    You do appreciate the difference between angular contact and deep groove ball bearings? Right?

    Your drawings and angles are attempting to apply angular contact bearing analysis to bearings that are not angular contact and do not carry loads in the way you have shown.
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  74. #74
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    Quote Originally Posted by Dougal View Post
    You do appreciate the difference between angular contact and deep groove ball bearings? Right?
    Not sure if it matters, considering the first link he offered me completely contradicts his "analysis".

    I was hoping to carry out a bit more of a Socratic dialog, but this could flame out at any minute...

  75. #75
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    This thread is a solution looking for a problem.

    I also find it laughable when people insist new standards are engineering driven. Engineering doesn't sell bikes, the 'appearance' of engineering-lite sells bikes.

    The Driver for BB30 is cheaper, easier mass production, all wrapped up in the over-simplified message of 'bigger is better'. It's not because of some irrefutable engineering excellence.

    I think for steel bikes especially, BB90 / BB86 has some pretty good attributes as part of the crank system as a whole, even if you take away Pete's singular argument.

    Who suggested a 44mm ID bottom bracket? Now THAT makes some big sense.
    No longer member of the bike industry nor society, so don't hassle me.

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    You guys rock, but please compare to the standard.

    IMO the BB30 was produced for volume frame manufacturing, especially with the carbon craze. If you look at a hand built Ti frame manufacture, they have no problems with the real estate available for welding a 2" bottom tube to a Standard English BB.

    Mojo

  77. #77
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    Just my two cents... PVD is kind of right. You can use BB30 Cranks in a BSA, there are BB Cups that can do that, so you can get the axle diameter out of the ecuation. On the other hand there are a few bikes using a new standar called BB386, yep BB30 size with BB86 Width, the best of both words.

  78. #78
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    Quote Originally Posted by pvd View Post
    Just so folks know, the more balls in a bearing assembly, the more friction on the system.
    It that why avid bb7's are better than avid bb5's?
    Keep trying to do the awesomest thing you've ever done.

  79. #79
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    I read the 2 pages, and I concluded that analyzing a single part is not the correct way to do things.
    A weekend rider, won't be able to "see" any advantages, other than: "OHHH... I have a XXXX BB!"
    A racer, will be see more flex on wheels and rear part of the frame, rather than cranks.

    A big BB shell permits a good stress flow - from BB to DT and ST. Basically forces are distributed evenly (or more evenly) at the junction.
    This is more thru with composite materials - more area - more strength.

    I haven't done the calculations with the Inertia and E values (both stell and Al.) but it is my belief that a spindle bigger in diameter (and thickness) made from Al, will be more rigid that a steel one. I will calculate and see.... nothing like maths.

    All are talking about Q-factor, etc, but on MTB I think the major factor is tire space so that no mud will accumulate in the stays. This will lead to a wider BB shell and a significant greater Q-Factor.
    Yes this can mitigate by 3 finger chainstays, and elevated chainstays, and everything, but design around that are will always be a balance and a compromise (like all mechanical things!)

    What I find great about BB30 is the fact that it isn't need a thread and in carbon frames, this is a great thing! On metal frames, this is not an issue, but tubes could be joined in a larger area (comparing BB30 BB shell and a "normal" BB shell.

    Regarding Q-Factor, I think in the real world, people don't care about it! They place the cleats where they find it more confortable, and sometimes that location is not the best one... people don't look for those small details.
    Because after Q-Factor, they should look at saddle position and angle/ center line and improving it with shims (improving the gears that they use more), cleat placement, and pedal methodology (yes... there a LOOOT of folks that just smash the pedals).

    Personally I find really annoying the fact that "standards" appear almost every week, and don't carry any REAL improvement other than the fact that it can bring real problems in maintain the bike, or finding parts on remote areas (outside cities).

    I really like the square cranks (call me retro...) and even with some problems that they would have.
    ISIS it was a real SH"#$%"#$!!!!
    And outside bearings - FOR ME, it's one good design that after installing can almost be forgotten!

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    I am a mechanical engineer someone may need to do a course in first principles (maybe the OP)
    My apologies to everyone on here for not adding anything to the thread but it would be a diatribe to nowhere

  81. #81
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    Quote Originally Posted by Tkul View Post
    I read the 2 pages, and I concluded that analyzing a single part is not the correct way to do things.
    A weekend rider, won't be able to "see" any advantages, other than: "OHHH... I have a XXXX BB!"
    A racer, will be see more flex on wheels and rear part of the frame, rather than cranks.

    A big BB shell permits a good stress flow - from BB to DT and ST. Basically forces are distributed evenly (or more evenly) at the junction.
    This is more thru with composite materials - more area - more strength.

    I haven't done the calculations with the Inertia and E values (both stell and Al.) but it is my belief that a spindle bigger in diameter (and thickness) made from Al, will be more rigid that a steel one. I will calculate and see.... nothing like maths.

    All are talking about Q-factor, etc, but on MTB I think the major factor is tire space so that no mud will accumulate in the stays. This will lead to a wider BB shell and a significant greater Q-Factor.
    Yes this can mitigate by 3 finger chainstays, and elevated chainstays, and everything, but design around that are will always be a balance and a compromise (like all mechanical things!)

    What I find great about BB30 is the fact that it isn't need a thread and in carbon frames, this is a great thing! On metal frames, this is not an issue, but tubes could be joined in a larger area (comparing BB30 BB shell and a "normal" BB shell.

    Regarding Q-Factor, I think in the real world, people don't care about it! They place the cleats where they find it more confortable, and sometimes that location is not the best one... people don't look for those small details.
    Because after Q-Factor, they should look at saddle position and angle/ center line and improving it with shims (improving the gears that they use more), cleat placement, and pedal methodology (yes... there a LOOOT of folks that just smash the pedals).

    Personally I find really annoying the fact that "standards" appear almost every week, and don't carry any REAL improvement other than the fact that it can bring real problems in maintain the bike, or finding parts on remote areas (outside cities).

    I really like the square cranks (call me retro...) and even with some problems that they would have.
    ISIS it was a real SH"#$%"#$!!!!
    And outside bearings - FOR ME, it's one good design that after installing can almost be forgotten!
    In a more simplified version of your statement: Bike designers/engineers will almost do anything, change anything and say anything to sell more bikes. Just can't leave well enough alone such as the tried and true BB68/73 outboard system.

    Mojo

  82. #82
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    no....
    If they can really prove that the design is better - then I'll buy it... when I break mine!
    If i have doubts... like in this mambojambo BS about bearing dimensions, I really don't bother even to start thinking in buying! I really like the external bearings, and find the crank rigid enough to not upgrade.

    Regarding weight... LOL! I have +3kg than what I suppose... so 200/300/400 grm in a bike is peanuts! Bike=15kg (16%), rider=80kg (84%)!
    This little differences (200/300/400grm) in "weekend racer" are peanuts...

    I look at something outside the normal BB68/73 and I see:

    Bigger diameter spindle and Bearings and BB shell
    Bigger BB shell --- >> Better interception and forms to attach the Seat Tube/Down Tube and chainstays

    Having this BB30 in steel, really don't make any sense!
    Steel wants slim tubes to make it lighter and more forgiven. Steel can handle some stress without breaking after 3/4 years of use.

    BB30 (and all others), make sense in Aluminium frames, where some down tubes are really enormous, or carbon where you have space (physical space) to place plies to attach all, or even use some square type downtube section in the interection area with the BB.

    Engineers normally don't sell anything! That's more with Commercials and Marketing departments... and sometimes they use the words that engineers talk during coffee!!!!

  83. #83
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    I was browsing the framebuilding forum for kicks and I stumbled across this thread. All I can say is wow. There is an incredible amount of disinformation in here.

    Here are some suggestions:

    Please start by drawing a valid FBD (free body diagram), this will start to point you in the right direction. There will be more than one load case you'll want to evaluate, so you'll have a few of them. This will define your bearing loads. They will be different for the different bearing configurations, in this case BB86 and BB30.

    L10 calcs and such will predict bearing fatigue life. There's also static load considerations too. You'll notice the two bearings have completely different capacities based on their parameters: ball size, count, and other factors etc. This will at least provide you an idea relative performance between the different bearings. The different configurations will have different loads applied to these different bearings that have different capacities. You need to normalize this all into expected life. A bearing that may have less capacity might be able to make up for it with different placement in the system where the loads might be lower.

    None of these simplified calculations take into account manufacturing variability that can affect proper fit of the bearings in the frames, sealing/external contamination or other potential failure modes to the bearings.

    As for the "stiffest". If stiffness is the goal, you need to look at the entire system: the frame, BB, spindle, crankset, wheel, etc - everything in the load path from the rider to the ground. The different bearing configurations of BB86 or BB30 might afford varying degrees of stiffness opportunities in the design of frame, crankset, spindle, etc that you aren't realizing. They are all essentially springs in series so in order to obtain on optimized solution the goal should be to balance all of their effective stiffnesses. If you're trying to stiffen up the one "spring" in the system that is already way stiffer than the others then it will have very minimal effect on the overall system stiffness and you are dealing with diminishing returns. You can also very easily cater the design to be optimized to stiffening one of those springs at the cost of adding flexibility to the others and you might end up in a wash or even more flexible. Don't get tunnel vision.

    Packaging constraints are another consideration, i.e. suspension linkages, tire clearance, chainrings. Different BB designs allow room in different ways.

    Cost is also a consideration. Cost is no object design constraints are easy.

    Weight is usually another, of course.

    Strength of course.

    It's an optimization problem trying to balance all of these targets and not every bike is designed for the same purpose nor does every manufacturer take the same approach.

    Some more disinformation regarding Q factor. Q factor being defined as where the pedals lie relative to frame centerline. The BB design is not the limiting factor here. It is the tire width and rear axle width which usually defines what the target chainline will be, then the chain itself (on a road bike try 53-11 and see how close your chain gets to the end of your crankarm, then account for deflection), the thickness of the crank on top of this and that all results in your Q-factor. Some frame designs might be more limited by the chainstay though. BB shell width has quite a bit of room to vary within this envelope and not affect Q factor. Just take a look for yourself. You will find most BB30 and other systems provide near identical Q factors. What BB30 will provide is allowance for a crankarm with more offset that provides more ankle clearance, which prevents heel rub on your crankarm. (Perhaps Q factor is getting confused with this, but they are different things) More important you get a shorter spindle which provides some stiffness benefits for left crankarm driving load cases, but remember consider the other "springs" in the system and how they might be affected by the narrower BB shell of the frame, could be better, could be worse. Would take some analysis.

    OK, that's my MTBR post for the year.

  84. #84
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    Press in BB's in steel bum me out...but then...Hmmm how about American BB shells and one piece cranks. There are lots of old bikes with 5/16 balls. I guess from a frame builder perspective a 44 mm Id would kick ass, Using the same bearings as headsets and 1.5 crank spindles??? Then we could devolve and start threading our head tubes....

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    Could someone explain what the difference between the BB30 you mention and the new External Press Fit (EPF). They seem to be the same as I can't find any data details on the EPF system.

    Kind Regards,

    Adam

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    The bearing will function far better the more the load is transferred perpendicular to the axis of rotation resulting in less fractional loss. I'll compare that later today, but its pretty obvious which system is better there. BB30 even goes so far as to specify very high angular bearings for use. Pretty lame.

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    Quote Originally Posted by flylyy
    The bearing will function far better the more the load is transferred perpendicular to the axis of rotation resulting in less fractional loss. I'll compare that later today, but its pretty obvious which system is better there. BB30 even goes so far as to specify very high angular bearings for use. Pretty lame.

    Quote Originally Posted by pvd View Post
    The bearing will function far better the more the load is transferred perpendicular to the axis of rotation resulting in less fractional loss. I'll compare that later today, but its pretty obvious which system is better there. BB30 even goes so far as to specify very high angular bearings for use. Pretty lame.
    Wierd

  88. #88
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    Sock meet puppet.

  89. #89
    pvd
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    Totally weird.

  90. #90
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    I think it's time for a ride!

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