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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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    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.

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    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.

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    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.

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    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.
    Owner of www.shockcraft.co.nz and NZ Manitou Agent.
    www.dougal.co.nz Suspension setup & tuning.
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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

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