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PostPosted: Tue Nov 26, 2013 8:30 pm 
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Location: Santa Cruz, California, USA
The various press-in bearing BBs can be lighter for the same stiffness, or stiffer for the same weight, than BSA threaded BBs. The cranks they allow can also be lighter for the same stiffness or stiffer for the same weight as BSA cranks.

BSA has serious problems- from an engineering standpoint external bearing threaded BB cups are silly, and the BSA standard is sized for tiny square taper spindles which are heavy, flexy and break. You can't fit both decent bearings and a reasonable diameter hollow spindle in the BSA shell.

There are a lot of theoretical advantages of press-in bearing BBs over BSA.

However press-in bearing BBs on bicycles tend to have a lot of practical problems (i.e. creaking). I'm not sure why because pressed in bearings work just fine in motorcycles and for bicycle wheel hub bearings. It could be that the torque loads are high for the bearing size or there are production problems (although non stepped standards like BB30 ought to be dead easy to manufacture accurately). Or maybe it's the bearings press fit into CF.

So while I'll argue that the pressed-in bearing BB is theoretically superior, right now GXP in a BSA BB is guaranteed to work right and is dead simple to install correctly. The GXP crank in my 2009 Cervelo is as free spinning as I have ever experienced and the preload never needs adjustment.


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PostPosted: Tue Nov 26, 2013 8:36 pm 
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Quote:
and the BSA standard is sized for tiny square taper spindles which are heavy, flexy and break. You can't fit both decent bearings and a reasonable diameter hollow spindle in the BSA shell.


My Campy square taper bikes would like to disagree with you!

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Posted: Tue Nov 26, 2013 8:36 pm 


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PostPosted: Tue Nov 26, 2013 10:04 pm 
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I just bought a new frame. Ridley Excalibur. I'm glad it has a British threaded bottom bracket shell. It will accept my 7900 Dura Ace threaded bearing cups from the prior frame. Maybe if I was buying a new crankset, an ultra light one, I would opt for one of these press in type bottom brackets. But for all of my existing cranks, give me British threaded. I have several Campagnolo ISO tapered bottom brackets that have been spinning smoothly for over 10 years. Silent and smooth. Yes heavy, but...


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PostPosted: Tue Nov 26, 2013 11:09 pm 
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eric wrote:
BSA has serious problems .... and the BSA standard is sized for tiny square taper spindles which are heavy, flexy and break.


'The Industry' is now giving traditional road brakes the same treatment as 'old fashioned' bottom brackets because it wants to sell us bikes with discs. Only that same industry has created a Mickey Mouse array of competing bottom bracket 'standards' in a pathetic game of marketing and mis-information.


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PostPosted: Tue Nov 26, 2013 11:18 pm 
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So true.... I hate having to knock PF30 bearings out with a puller when they need to be replaced or maintained. Also, having to use a head set press to install a BB bearing stinks (even though I own one). Used to be a 5min job you could easily do anywhere with HT II/GXP BB's.

I also now have several frames with internal cable or di2 routing that goes through the BB shell area... any time I need access to that area on my PF30 frames, everything has to come apart. Less than ideal.


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PostPosted: Tue Nov 26, 2013 11:55 pm 
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My verdict is threaded BSA- nothing wrong with this setup. Never was, never will.
I have used various PF30 setups with mixed success. Carbon bikes tend to be better, but occasionally the bb shell is not perfectly round and they make noise or eat bearings. I would never own a metal (steel or ti) bike with a PF30 bb. I do not trust that one can be made that does not make noise.
I wish a bike company would make a road version of what Santa Cruz does on the dirt (with bikes like the 5010). Threaded bb, press-in taper headset, external cables. Then the bike would shift great, bearing would turn smoothly, and it would not make noise.


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PostPosted: Wed Nov 27, 2013 12:02 am 
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bikerjulio wrote:
My Campy square taper bikes would like to disagree with you!


I'm sure they'd like to but they'd be wrong. I weighed the Campy road spindle I keep in the tool box to club intruders over the head with. It's 143g. The closest modern equivalent (just a spindle) would be the Cannondale BB30 spindle. The one weight I can find is 105g for a 132mm long model, which I think is for MTB and thus heavier than a road spindle.

Its much larger diameter is stiffer than the steel Campy spindle even though it is lighter, made from aluminium and is hollow. And it has much larger crank arm to spindle mating surfaces making a more secure interface than the tiny square taper. Square taper is like toe clips and straps- old tech that I don't miss at all.


Discs do have some advantages over rim brakes, most notably wet weather braking. There is a reason why XC MTB racers run discs even though they are heavier than rim brakes. If I were building a dedicated rain bike rather than using my oldest road bike, I'd get discs (and fender mounts). But to me it's not worth building a new bike.

Of course with all new tech there's marketing hype- that's what marketing people do. But just because something is marketed doesn't mean that it doesn't have an advantage of some sort. You have to decide if the real advantage is worth it to you.


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PostPosted: Wed Nov 27, 2013 12:20 am 
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one more advantage for some pressfit BBs - wider shells allow room for substantial chainstays, yet also allow more room for tires, which seem to be growing. Specialized's SL4 can't take a Zipp 303 rear wheel, likely because they had stiffness targets in a space constrained package.


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PostPosted: Wed Nov 27, 2013 12:52 am 
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Calnago wrote:
None of the new "standards" work as well and are as trouble free as BSA standard threaded.


+1

I've ridden and wrenched seven standards over the years (and know how to wrench properly). The newer standards have some adavntages, but BSA is the only consistently set and forget option.


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PostPosted: Wed Nov 27, 2013 1:02 am 
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I'm just wondering how many people above ridden different bb shell frames?
Having said this, by any means I'm not the expert, but for me there is a significant difference between canyon clx bsa and cervelo bbright, both frames I was riding for a quite long time. And if the feeling is due to bb shell, I vote for bb30 ish and more :wink:

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PostPosted: Wed Nov 27, 2013 1:08 am 
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Location: New Zero Kanada 43° 40' 0" N, 79° 25' 0" W
I'm pleased that most people - and people who are generally willing to try new stuff - agree and understand that BSA is better than the various press fit options.

Of course, no one has brought to market the better option of an oversized threaded BB system. This would blend the superior threaded interface with the materials' advantages offered by OS. Sadly, this isn't likely to happen because companies would lose the manufacturing and assembly efficiency advantatages of a no-thread system. Sad.


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PostPosted: Wed Nov 27, 2013 1:11 am 
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eric wrote:
bikerjulio wrote:
My Campy square taper bikes would like to disagree with you!


I'm sure they'd like to but they'd be wrong. I weighed the Campy road spindle I keep in the tool box to club intruders over the head with. It's 143g. The closest modern equivalent (just a spindle) would be the Cannondale BB30 spindle. The one weight I can find is 105g for a 132mm long model, which I think is for MTB and thus heavier than a road spindle.


Yes there is a difference in weight - but incrementally so, not massive.

In say 2004 or thereabouts a Record BB was 190g and Carbon crankset 580g for a total of 770g.

More recently a Record UT setup is 55g for the cups and around 650g for the crankset or a total of 705g.

So, about a 9% improvement.

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PostPosted: Wed Nov 27, 2013 3:27 am 
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I back myself to have a reasonable amount of power on a road bike, yet to find noticeable flex from a Ti bike with an English BB and 7800 cranks.

Funnily enough, can feel the stiffness difference between my GXP carbon cranks and the Rival GXP cranks.

But lets keep blaming spindle and BB size for flex...


#stickwithBSA

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PostPosted: Wed Nov 27, 2013 3:55 am 
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One question very few people cared to spell out was WHAT STIFFNESS are we trying to improve? Spindle stiffness? or down tube/bb shell/chainstay stiffness? The 30 camp is focused on the former, and the (3)86/90 camp focuses on the latter.

I'd be interested in seeing some separate data on spindle deflection versus frame deflection.

Another very important feature of BSA is the self centering effect of threads, which give you much greater tolerance than press-fit.

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PostPosted: Wed Nov 27, 2013 4:21 am 
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elviento wrote:
One question very few people cared to spell out was WHAT STIFFNESS are we trying to improve? Spindle stiffness? or down tube/bb shell/chainstay stiffness? The 30 camp is focused on the former, and the (3)86/90 camp focuses on the latter.

I'd be interested in seeing some separate data on spindle deflection versus frame deflection.

Another very important feature of BSA is the self centering effect of threads, which give you much greater tolerance than press-fit.


Valid points Elviento... but I still think the whole stiffness issue, or whatever the marketing people want to come up with to try to sell this, is a red herring. I think you realize, since you probably have more experience seeing the actual process in manufacture than anyone on this thread at this point, that building a molded frame around a perfectly aligned threaded bottom bracket shell presents manufacturing challenges and cost that are so easily avoided by, well... just leaving a big hole there and trying to make it round enough so that the end user can press some cups in after the fact and call it good. Plus, without that big heavy shell in there, our frames will weigh less too... and that sells. Oh, and for those frames that are bit out of tolerance, just tell them to Loctite the hell out of it till it stops. Not our problem.

As to the threads, they do provide some self centering by design, and with the introduction of outboard bearings in threaded bottom bracket, I can't stress enough how important it is to properly face the BB shell once again, just like the old days. Install a Campy Super Record Cult crank into a properly faced threaded BB shell, and that thing spins like nothing else. Don't face it, and well... you get what you put into it.

Campy's attempt at adapting to the pressfit bb shells had some issues, largely due to the finely machined alloy cups which might seem like a good thing. Until you try to press them into frames that have been manufactured to tolerances much less than the matching cups. Creak creak creak. We'll see how Campy's new cranks for the new "standards" fare in the coming year I suppose.

But given the choice, I would still opt for the only "standard" that we still have and that can be legitimately labeled a "standard",... the BSA 68mm threaded shell. Widening everything down there presents some challenges too, with crank profiles, Q-factors, and I'm sure some other stuff. The whole affair has just created a minefield of confusion and problems that just simply weren't there before all of these "innovations" started.

Let's be clear, the move towards pressed in bottom brackets has much more to do with ease of manufacture and cost to produce than providing any real benefit to the rider. I suppose if they eventually get it right, and really do solve all the tolerance and compatibility issues then it won't really matter, but so far... they haven't.

Is that more than 2 cents worth... I wasn't counting.

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Posted: Wed Nov 27, 2013 4:21 am 


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