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  1. #1
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    Shimano Press Fit BB - for Pete (and anyone else)

    Quote Originally Posted by pvd
    No. Shimano will win. I blame the problem on the framebuilders that don't have the common sence to go BB92 instead of BB30. It's so painfully obvious that it's discusting. Wtf?
    1. sense
    2. I'm far from the smartest guy here but it's not obvious to me WTF you're writing about here
    3. disgusting

    I can seen an argument against BB30 from a MFG point of view but BB92 and PF30 are very similar from the builders perspective. They hold different bearings in different places for different cranks. Functionally, BB92 isn't any better than a standard BB. I wouldn't make the argument that PF30 is better than a standard BB either, it just facilitates the use of different cranks.

    Qualify your statements Pete.
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  2. #2
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    I think it's a case of for Steel and Ti at least, bigger BB's aren't doing us any favours. They're heavier, they don't make our frames any better or cleaner to manufacture, and few can see the benefit of having to spend an entire morning jigging up a frame on a mill so the BB can be bored to a ridiculous tolerance.

    I agree with you Sean, I don't see BB92 or PF30 being any different. I also don't see either bring to us Steel and Ti guys anything of real value aside from 'keeping up with the Giants'.

    With your 44mm headset for tapered forks, I see real-world benefits, but press-in BBs I don't functionally or aesthetically see any. Well actually I think the BB92 does look pretty cool, but BB30/PF30 looks out of place.
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  3. #3
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    I disagree Warwick. Many of these systems can simply be reamed (by hand) after construction and don't need to be put in a mill, although that is an alternative that would work. Some of the press fit options also use the ends of the BB to locate the bearing cups and don't rely solely on the ID. The wider BB, like BB92, can help with CS/tire clearance on certain bicycles, so they do have their place. From an engineering standpoint, the bearings are better supported than they are with external cups on a traditional BB.
    Too many bikes, not enough time.

  4. #4
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    Interesting discussion.

    BB92: thin plastic cup around bearing = never getting BB stuck in the BB shell again because you forget to service the bike (not sure if BB30 does this or not.) I've not used one (yet) but I would think this reduces creaking too compared to thread in?
    BB92: wider set chainstays. The non-drive side one is easy. The drive side can use things like a forked plate (can't remember the builder) and still retain small crank ring clearance.
    BB92: Snap to ream/face w/ hand tools (that aren't really avail yet since the US refuses to go metric)
    BB92: Not applicable to most of us: superior in carbon frames since there is a wider joint avail to distribute crank forces. Can either make bike lighter or stiffer (or combination)

    Warwick brings up an interesting point - weight. The shell diams are similar.
    BB92 92mm wide vs BB30 68 = 35.0% more matl
    Would need FEA to know how the width affects the forces to see if you could butt more and trim that difference.

  5. #5
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    BB30: blah blah blah
    BB92: blah blah blah
    pressfit 30: blah blah blah

    SQUARE TAPER: i aint going no where

  6. #6
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    For the record, the wider shells don't actually have a practical advantage when it comes to chainstay spacing and tire clearance/ring. You're still constrained by the location of the chainrings and the thickness of the drive side stay. Any problem you're going to have RE clearances, you're still going to have it if you choose to build to a BB92 vs a standard 73mm shell.

    You could argue that the larger diameter shells such as the PF30 allow you to build with slightly more chainring clearance if you miter the bottoms of the stays tangent to the BB shell.
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  7. #7
    pvd
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    BB92-

    Gives a wider separation of the stays at the BB. Better.

    Improves the stiffness of the rear end given the same stays.

    Presses directly into carbon BBs.

    Wider mount for suspension parts.

    The bend is reduced getting to the stays making things easier on the tube.

    The diameter of the shell is large giving a good platform for big down tubes.

    Easy to make via simple ream thru

    Really light shell



    BB30 -

    Post welding machining of a snap ring groove. HAhahahaha!

    Bearings pressed directly to metal frame. Can you say Fat City! The worst system ever.

    68mm wide. Dumb.

    Silly big spindle. Why? Nobody knows.

    Heavy a$$ shell

    Totally dead standard.



    PF30:

    Better than BB30. That's about it.






  8. #8
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    Quote Originally Posted by pvd
    Easy to make via simple ream thru
    The 9.3mm depth you have in your wiki, thats only the minimum depth? The plastic cups are what limit the bearing insertion?

    Lynskey is who I was thinking of. One of these + BB92 could give the ultimate in clearance.
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  9. #9
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    Quote Originally Posted by pvd
    BB92-

    Gives a wider separation of the stays at the BB. Better.
    Why? What's the benefit? Show your work.

    Quote Originally Posted by pvd
    Improves the stiffness of the rear end given the same stays.
    Making this statement, without proof, is in the same ballpark as the BB30 folk claiming stiffer cranks. Prove it. I not only want you to prove your statement with some relative stiffness numbers, but I'd love to hear your take on why it would be relevant if it is true. I own two bikes built for "BB92" shells and I can't tell a bit of difference, just like I can't tell the difference between my BB30 cranks and the XTR 960's I had before. Mind you, this is FAR from me stating that there's no difference, I just can't feel it.

    Quote Originally Posted by pvd
    Presses directly into carbon BBs.
    OK

    Quote Originally Posted by pvd
    Wider mount for suspension parts.
    OK

    Quote Originally Posted by pvd
    The bend is reduced getting to the stays making things easier on the tube.
    What's the benefit of the reduced bend? You can bend tubes all day. If done right and discounting material problems there's no issue.

    Quote Originally Posted by pvd
    The diameter of the shell is large giving a good platform for big down tubes.
    no argument here

    Quote Originally Posted by pvd
    Easy to make via simple ream thru
    BB30 and PF30 both require a post weld bore or ream if that's your style. Most BB30 shells already have the snap ring groove in place, no additional work. WRT process, it's a wash, there's no benefit to BB92

    Quote Originally Posted by pvd
    Really light shell
    "really light" isn't data. A 1.5 x 73mm Paragon shell weighs 102g. King cups weigh108g.
    I'll weigh the Shimano cups later today and will edit this post. What does your shell weigh?

    I know you're an intelligent guy, Pete, but spouting off a bunch of purposeless BS isn't doing anyone any good and someone out in interwebland is believing what you're writing.
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  10. #10
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    Quote Originally Posted by smudge
    Most BB30 shells already have the snap ring groove in place, no additional work.
    Can't face the shell if the snap ring grooves are already there. Do they make the shells a little extra wide to acct for that? If they make them on the +tol side, would have 0.4mm per side which is prob enough to account for the top of the shell shrinking from the welds. The snap ring grooves won't remain parallel though...

  11. #11
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    Quote Originally Posted by smdubovsky
    Can't face the shell if the snap ring grooves are already there. Do they make the shells a little extra wide to acct for that? If they make them on the +tol side, would have 0.4mm per side which is prob enough to account for the top of the shell shrinking from the welds. The snap ring grooves won't remain parallel though...
    No need to face a BB30 shell as the bearing has no contact at all with the face and relies solely on the ID of the shell and the snapring location as a stop. The shells are initially turned undersized with the snap ring bore sized to spec. That way, only a boring/reaming operation needs to be performed.You're right that the grooves don't remain parallel but you don't need to press the bearings far enough in to make full contact with the snap rings.

    That said, and I've written this before, now that PF30 is available, I'll never build another BB30 frame. They accomplish the same thing but PF30 shells are slightly less finicky to build with.
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  12. #12
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    Quote Originally Posted by smudge
    No need to face a BB30 shell as the bearing has no contact at all with the face
    Ahhhhh. (little lightbulb above head appears)

  13. #13
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    Quote Originally Posted by smudge
    For the record, the wider shells don't actually have a practical advantage when it comes to chainstay spacing and tire clearance/ring. You're still constrained by the location of the chainrings and the thickness of the drive side stay. Any problem you're going to have RE clearances, you're still going to have it if you choose to build to a BB92 vs a standard 73mm shell.
    Sean I agree with what you said for >99% of frames. However, I was purposely vague in what I posted above because it's possible to imagine a combination, albeit rare, of single chainring bike with super short CS where you can gain tire clearance with this combo. You are still correct that most frames will be limited by chainring clearance.

    Wider pivot mounting on full suspension bikes is likely to be one of the most tangible benefits of this wider shells.
    Too many bikes, not enough time.

  14. #14
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    "really light" isn't data. A 1.5 x 73mm Paragon shell weighs 102g. King cups weigh108g. I'll weigh the Shimano cups later today and will edit this post. What does your shell weigh?

    SM-FCM970 Shimano BB92 pressfit cups and sleeve 71g actual.

    The system might be 15-20g lighter than your standard external BB setup, which isn't exactly anything to write home about.
    No longer member of the bike industry nor society, so don't hassle me.

  15. #15
    DWF
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    Anecdotal evidence, but we've been selling more Shimano PF adapters than all the rest. Then PF30s. I can't give BB30's adapters away and I still have about 100 sets of them.
    A man must have enemies and places he is not welcome. In the end we are not only defined by our friends but those against us.

  16. #16
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    Quote Originally Posted by DWF
    Anecdotal evidence, but we've been selling more Shimano PF adapters than all the rest. Then PF30s. I can't give BB30's adapters away and I still have about 100 sets of them.
    Ah, that's the data I want. What other tidbits can you clue us in on?

  17. #17
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    Quote Originally Posted by HomeGrownSS
    BB30: blah blah blah
    BB92: blah blah blah
    pressfit 30: blah blah blah

    SQUARE TAPER: i aint going no where
    I've still got 2 square taper BB's I've had since the early to mid 90's that still work well. Yea they are a pain in the arse to pull, but they have stood the test of time. Where's ISIS, Octa Link v1 and v2??

  18. #18
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    It would be interesting to hear from Don in regards to any changes in the uptake pattern here.

    Truls

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