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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?

  13. #13
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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.

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    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.

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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.

  20. #20
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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.

  25. #25
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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.

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