# Some Inherent Weaknesses of External Bottom Brackets



## aka brad (Dec 24, 2003)

Recently there has been some discussion about bottom brackets and specifically the superiority of external bottom brackets (bb). While researching why Shimano and Campagnolo did not have external bb in their Track/Pista gruppo, some interesting facts came up regarding the weaknesses of external bb. The first is the fact that external bb are not supported by the inside of the bb shell. External bb bearing are in cups outside the bb shell. This causes the spindle to wobble, reducing smooth pedaling and bearing life. Further, the whole point of external bb are larger bearings for larger dia spindles. Unfortunately larger bearing also mean there are less points supporting the spindle; this also increases the tendency of the spindle to wobble. My take on this is there is a point of diminishing returns with bearing size and the old square taper seemed to have gotten right. Another issue with external bb is the tightness of the seals, which causes more drag on the spindle of internal bb. Keirin racers are known to still use loose ball bb, even though Octalink is NJS certified. They do this because the loose ball are not sealed and they can use oil instead of grease when they race, both reducing bb drag. I have said this before, that I believe that the BB30 will probably replace external bb, as it still supports the bb bearings inside the shell and still allows for a larger dia spindle. If there is a weakness with square taper, it might be its inability to withstand some 10'+ drops. Yes, the larger dia spindle will withstand the drop, but it's only a matter of time before the poorly supported bearings fail. So you might want to think twice before you upgrade to to external bb. The only reason I can think of is to use the uber cool Forward Components EBB converter.


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## Tone No Balone (Dec 11, 2004)

yes.....after years of using external BB's on my geared bikes I recently switched back to square taper (WI ENO Crank) on my 29er SS and was wondering why I ever switched in the first place! No drag, smooth pedaling, virtually no mantainence.....sweeeeet!


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## DiDaDunlop (Oct 22, 2005)

aka brad said:


> ..... The first is the fact that external bb are not supported by the inside of the bb shell. External bb bearing are in cups outside the bb shell. This causes the spindle to wobble, reducing smooth pedaling and bearing life. Further, the whole point of external bb are larger bearings for larger dia spindles. Unfortunately larger bearing also mean there are less points supporting the spindle; this also increases the tendency of the spindle to wobble. .....


How do you mean "less points supporting the spindle? Lager bearings have a larger internal circumference which, in theory, should mean more contact points. I may be inclined to think that square taper bearings are wider and therefore less prone to wobble. But they are closer to eachother so wobble is a bit more exaggerated. Tits for tats. But I would love some more info.

My main gripes about external bearings are the seals and the tiny bearings compared to square taper. The spindle is bigger and therefore less flexier. But hey I think that those differences and neglible compared to possible frame flex and lower body flex. Also modern square taper BB are pretty bomber and need zero maintenance (except for those 10' drops). Compare that to the multitude of extra parts/setup for a External BB.

BB30/90 should solve a lot of the above mentioned problems. But I anxiously await the first damaged frames from not perpendicular axles/bearings. HS cups are also pressed in but the bearings are supported bij the cups not the frame. Which is also my main gripe about some of those internal HS.


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## DiDaDunlop (Oct 22, 2005)

Ah found your reasoning in another post. 

"This raised questions about durability and stability, but also a couple teams observed that under track conditions the axle tended to ride up and down a bit on each bearing and wasn't supported as well as with an internal bottom bracket."

Which is understandable because the spindle of external BB's simply does not has a good press fit in the bearings. Square taper/octalink and the like have pressed on bearings and the crank is bolted (removable press fit) to the spindle.


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## b1umb0y (Feb 28, 2005)

That is always the entertaining part of theory vs. reality... Your reasoning is very cogent with regard to why an OBB would fail prematurely, but in reality, I haven't seen the lower life span on OBBs*. 

*I know certain brands have failed miserably in this realm (of OBB), but those brands did not have a well designed method for pre-loading the bearing. Those designs that did address this issue are exhibiting respectable life spans. 

In the end, I have had great experiences with taper-, Octalink, ISIS, and OBB bottom brackets. Likewise, I have had horrible experiences with all of the above. 

There is no single truth... no panacea.


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## forwardcomponents (Dec 2, 2008)

aka brad said:


> Recently there has been some discussion about bottom brackets and specifically the superiority of external bottom brackets (bb). While researching why Shimano and Campagnolo did not have external bb in their Track/Pista gruppo, some interesting facts came up regarding the weaknesses of external bb. The first is the fact that external bb are not supported by the inside of the bb shell. External bb bearing are in cups outside the bb shell. This causes the spindle to wobble, reducing smooth pedaling and bearing life. Further, the whole point of external bb are larger bearings for larger dia spindles. Unfortunately larger bearing also mean there are less points supporting the spindle; this also increases the tendency of the spindle to wobble. My take on this is there is a point of diminishing returns with bearing size and the old square taper seemed to have gotten right. Another issue with external bb is the tightness of the seals, which causes more drag on the spindle of internal bb. Keirin racers are known to still use loose ball bb, even though Octalink is NJS certified. They do this because the loose ball are not sealed and they can use oil instead of grease when they race, both reducing bb drag. I have said this before, that I believe that the BB30 will probably replace external bb, as it still supports the bb bearings inside the shell and still allows for a larger dia spindle. If there is a weakness with square taper, it might be its inability to withstand some 10'+ drops. Yes, the larger dia spindle will withstand the drop, but it's only a matter of time before the poorly supported bearings fail. So you might want to think twice before you upgrade to to external bb. The only reason I can think of is to use the uber cool Forward Components EBB converter.


I am glad that somebody initiated this discussion. I have been thinking about this issue as well.

While looking at the Phil Wood site, I noticed something very interesting. As everyone knows, Phil Wood is noted for two things: very high quality bearings and seals, and square taper bottom brackets. What many people do not know is that Phil Wood also makes outboard bearing bottom brackets, as well as the bearings and seals for them.

https://www.aspirevelotech.com/images/Phil_Wood/OutboardBearingCupsWW.jpg

It is interesting to note that the Phil Wood outboard threaded cups are made from stainless steel, not aluminum. No doubt these are heavier, but one can only speculate that they are much less flexible, and provide a more stable housing for the bearings. Phil Wood obviously feels that it is possible to make an outboard bearing bottom bracket that is up to his high standards for bearing durability. The industry people I have spoken with have all told me that his outboard bottom bracket replacement bearings outlast all the others. Obviously it is possible to make a bearing for this system with exceptionally good life expectancy. The difference is in the details, as usual.

As for bearing size, both of Phil Wood's systems use balls that must be almost exactly the same size. The dimensions of their square taper cartridge bearings are 17mm x 30mm x 7mm. The dimensions for their outboard system cartridge bearings are 25mm x 37mm x 7mm. Do the math, and you will see that the difference in ball diameter is probably 0.5mm, assuming that the races are equally thick. It is possible that both systems use identiacl ball sizes. Tha fact that both systems use cartridges that are the same 7mm width suggests that this is probably true.

Phil Wood is obviously confident that outboard bearing systems can have the durabilty that his customers expect, and experience seems to be proving him right. I think that the issues associated with currently available outboard bearings have more to do with failures in bearing cup, bearing, and seal design rather than any inherent flaws in the system itself.

Are external seals absolutely necessary on outboard bearings? Since the introduction of cartridge bearings and cartridge bottom brackets, one lip seal has been the design standard. All of these designs, including good examples such as Phil Wood, or the venerable Shimano UN-72 square taper cartridge bottom bracket, use one lip seal on the bearing, with no external seal. The bearing industry has always claimed that external seals are preferable, be they lip seals, dust seals, or labyrinth seals. They are better than one seal if designed properly. Despite this, excellent products have been made without them, as the two examples show.

Phil Wood
https://www.cambriabike.com/Images/product/phil_wood_steel_bottombracket.jpg

UN72
https://farm1.static.flickr.com/4/3937021_609d2ab488.jpg?v=0


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## j e SS e (Dec 24, 2007)

I've been saying since I've had to work on them; it's unfixing something that works beautifully in the first place. 

Externals, IMO, have more to do with marketing, business and R&D guys keeping their jobs than an improvement to an existing system, which it clearly is not.


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## EBasil (Jan 30, 2004)

Both of those bottom brackets are fine examples of square-taper specimens, but this discussion is comical in the manner of scientific "proof" that the world is flat. I bet we can find another thread (or nine) about how rigid bikes are far more efficient, faster, smarter, better, whatever, than suspension bikes. C'mon, who was around for all that? 

I've been to the edge, from there I stood and looked down. I've ridden square tapers, built bikes with square tapers and broken square tapers. I've ridden external, since 1995 on my main ride, built with external and worn out bearings in external. The earth may be flat where you are, and that's GREAT -- I am stoked for you. But despite all your Creation Science and various apocrypha, things are not as you think. Cute, charming and even quaint, but for those of you getting all worked into a froth trying to convince us, also silly.

If you like square taper, if it makes you feel core or fast or happy, by all means: use it in good health! Get yourself a qualtiy product with a short spindle and some strong cranks. The only thing you'll be flexing is your bottom bracket shell, and it will last a good long time. There's no need to leave the valley, all you need is here.


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## bikeny (Feb 26, 2004)

aka brad said:


> Recently there has been some discussion about bottom brackets and specifically the superiority of external bottom brackets (bb). While researching why Shimano and Campagnolo did not have external bb in their Track/Pista gruppo, some interesting facts came up regarding the weaknesses of external bb. The first is the fact that external bb are not supported by the inside of the bb shell. External bb bearing are in cups outside the bb shell. This causes the spindle to wobble, reducing smooth pedaling and bearing life. Further, the whole point of external bb are larger bearings for larger dia spindles. Unfortunately larger bearing also mean there are less points supporting the spindle; this also increases the tendency of the spindle to wobble. My take on this is there is a point of diminishing returns with bearing size and the old square taper seemed to have gotten right. Another issue with external bb is the tightness of the seals, which causes more drag on the spindle of internal bb. Keirin racers are known to still use loose ball bb, even though Octalink is NJS certified. They do this because the loose ball are not sealed and they can use oil instead of grease when they race, both reducing bb drag. I have said this before, that I believe that the BB30 will probably replace external bb, as it still supports the bb bearings inside the shell and still allows for a larger dia spindle. If there is a weakness with square taper, it might be its inability to withstand some 10'+ drops. Yes, the larger dia spindle will withstand the drop, but it's only a matter of time before the poorly supported bearings fail. So you might want to think twice before you upgrade to to external bb. The only reason I can think of is to use the uber cool Forward Components EBB converter.


I think you have some good points and some that are not so good. First, on a mountainbike, you cannot use a square taper BB with loose bearings, no seals, and oil. It just won't last long. Sure, it will feel great for the first ride, but after that it will get gunked up. But it does bring up one of the main complaints about external BBs, namely the drag associated with the bearing and seals. This is definately noticable when spinning the cranks by hand, but I am not sure how much of a difference it actually makes will riding. I am not sure what you mean by less points of contact, I assume you mean less balls in the bearing? I don't think that is correct. I would think the external BB, because it uses larger I.D. and O.D. would have more balls, or at least larger balls which can support more load. As far as spindle wobble, I would think you would get less with the external BB system. Basically because the spindle is supported further out and because the spindle itself is much stiffer. Now I agree that if the BB shell was wider to the point that the bearings ended up in the same place as an external BB system, that would be better than everything else. I am not familiar with the BB30 system, maybe that is what it does.

I think the needs of Keirin racers are drastically different than that of MTB riders. A little extra drag is perfectly acceptable if it results in longer lasting bearings and a stiffer system.

Mark


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## j e SS e (Dec 24, 2007)

bikeny said:


> I think you have some good points and some that are not so good. First, on a mountainbike, you cannot use a square taper BB with loose bearings, no seals, and oil. It just won't last long. Sure, it will feel great for the first ride, but after that it will get gunked up. But it does bring up one of the main complaints about external BBs, namely the drag associated with the bearing and seals. This is definately noticable when spinning the cranks by hand, but I am not sure how much of a difference it actually makes will riding. I am not sure what you mean by less points of contact, I assume you mean less balls in the bearing? I don't think that is correct. I would think the external BB, because it uses larger I.D. and O.D. would have more balls, or at least larger balls which can support more load. As far as spindle wobble, I would think you would get less with the external BB system. Basically because the spindle is supported further out and because the spindle itself is much stiffer. Now I agree that if the BB shell was wider to the point that the bearings ended up in the same place as an external BB system, that would be better than everything else. I am not familiar with the BB30 system, maybe that is what it does.
> 
> I think the needs of Keirin racers are drastically different than that of MTB riders. A little extra drag is perfectly acceptable if it results in longer lasting bearings and a stiffer system.
> 
> Mark


Enough with all the "balls" and "loads", we're talking bike parts here.....

One problem is everyone's obsession with q-factor. It seems like everyone wants their feet tied together rather than spread apart a bit for better balance and power.

The other problem is everyone's obsession with stiffness. Whatever doesn't bend will break. There needs to be some flex to help bear the load. Bridges flex. Skyscrapers flex. If they didn't they would fail prematurely. Crank/BB/Spindles need to have some flex in there somewhere, too. Especially with increasingly "laterally stiff, vertically compliant" frame designs.

Narrower and stiffer but lasts as long or longer ain't gonna happen.

Internals are much better supported and the bearings, typically, last much longer.

The industry is loving it though, think how many more BB they sell now than when everything was square tapers that last forever.

When things work too well, in any industry, the tendancy is to "improve" the design, which results in something that requires more maintenance and/or replacement. It's how they make more money. Manufacturers don't make as much money with product designs that don't need maintenance or replacement.


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## Norris_Hanna (Apr 7, 2009)

Tone No Balone said:


> yes.....after years of using external BB's on my geared bikes I recently switched back to square taper (WI ENO Crank) on my 29er SS and was wondering why I ever switched in the first place! No drag, smooth pedaling, virtually no mantainence.....sweeeeet!


I have been working on bikes since 1980 and then got out altogether for a period of time when the external BB rose up. I have an external on one of my bikes and don't see it to be any better than square taper BB's and certainly not an advantage. The Sq.Ta BB's were simple (especially the cartridge style), relatively lightweight, strong enough for most purposes, and they work.... what more do you want? I too still prefer the square taper style, newer is not always better. I may be teetering on "retro-grouch" status but I believe most of the new products and new product hype are based soley on selling people more junk that they really don't need and keeping the bike business lucrative.


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## wv_bob (Sep 12, 2005)

EBasil said:


> The earth may be flat where you are, and that's GREAT -- I am stoked for you. But despite all your Creation Science and various apocrypha, things are not as you think.


I knew it was going to be a good post when you quoted some Van Halen lyrics.

Yes, the choice between square taper and external BBs is very much like the choice between being a flat earther or a scientist, or having to choose between believing in evolution or intelligent design. I don't know why I didn't see it sooner.

Someone oughta come up with the equivalent of the Flying Spaghetti Monster for square taperists to worship. I suggest an image of Jobst Brandt be included in it somewhere.


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## aka brad (Dec 24, 2003)

bikeny said:


> I think you have some good points and some that are not so good. First, on a mountainbike, you cannot use a square taper BB with loose bearings, no seals, and oil. It just won't last long. Sure, it will feel great for the first ride, but after that it will get gunked up. But it does bring up one of the main complaints about external BBs, namely the drag associated with the bearing and seals. This is definitely noticeable when spinning the cranks by hand, but I am not sure how much of a difference it actually makes will riding. I am not sure what you mean by less points of contact, I assume you mean less balls in the bearing? I don't think that is correct. I would think the external BB, because it uses larger I.D. and O.D. would have more balls, or at least larger balls which can support more load. As far as spindle wobble, I would think you would get less with the external BB system. Basically because the spindle is supported further out and because the spindle itself is much stiffer. Now I agree that if the BB shell was wider to the point that the bearings ended up in the same place as an external BB system, that would be better than everything else. I am not familiar with the BB30 system, maybe that is what it does.
> 
> I think the needs of Keirin racers are drastically different than that of MTB riders. A little extra drag is perfectly acceptable if it results in longer lasting bearings and a stiffer system.
> 
> Mark


A few clarifications. 1)I errored when I said fewer contact points. What I meant was the contact points were father apart. 2)The problem with the idea of the spindle being supported by points father apart is the poor support of the bearings. In this case it is an aluminum cup outside the shell threaded into the shell. With an internal bb, the side loading forces on the bearings are mitigate by the beairngs being supported inside the shell. With an external bb, there is no outside rigid shell holding the bearings in line. The interior bottom bracket bearings are held perpendicular to the spindle to prevent side loading and premature wear or failure of the bearings. The external bb cups are screwed into the ends of the shell and therefore not are held into place by a surrounding rigid steel housing. Therefore the bearings simply cannot be held as secure, creating more side loading and wobble.3) Finally, I did not bring up the Keirin racers to suggest that we should be using unsealed bearings. I simply wanted to demonstrate that seal drag does count for something. The nature of an external bb means both bearings need to be sealed on both sides. And while you may not feel it when you are riding, it does slow you down; so why have more of it is not necessary?


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## DiDaDunlop (Oct 22, 2005)

> In this case it is an aluminum cup outside the shell threaded into the shell


Aren't HS cups made in the same way? Also supported outside the shell by an alu cup.

main difference in my opinion is that HS bearings have much better clamping and preloading system. Also HS bearings get a much bigger beating in my opinion. But because of the large cups and better preload system HS bearings are much more able to withstand the abuse.


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## bikeny (Feb 26, 2004)

aka brad said:


> A few clarifications. 1)I errored when I said fewer contact points. What I meant was the contact points were father apart. 2)The problem with the idea of the spindle being supported by points father apart is the poor support of the bearings. In this case it is an aluminum cup outside the shell threaded into the shell. With an internal bb, the side loading forces on the bearings are mitigate by the beairngs being supported inside the shell. With an external bb, there is no outside rigid shell holding the bearings in line. The interior bottom bracket bearings are held perpendicular to the spindle to prevent side loading and premature wear or failure of the bearings. The external bb cups are screwed into the ends of the shell and therefore not are held into place by a surrounding rigid steel housing. Therefore the bearings simply cannot be held as secure, creating more side loading and wobble.3) Finally, I did not bring up the Keirin racers to suggest that we should be using unsealed bearings. I simply wanted to demonstrate that seal drag does count for something. The nature of an external bb means both bearings need to be sealed on both sides. And while you may not feel it when you are riding, it does slow you down; so why have more of it is not necessary?


OK, you make some good points again. You may be correct that contact points are further apart, I have not looked at the actual bearings being used, but there are definately more of them in and external BB, so that should increase the load carrying capacity. Although, if the same size ball is being used, the distance would be the same. I have very limited experience riding an outboard bearing system, but here is my take: The external BB system is stronger than a sqaure taper system. I believe it is also a stiffer system overall. I also think there is more drag than on a square taper system. This can certainly be felt when turning the cranks by hand. BUT, I don't think this is noticeable at all while riding, and probably has a negligeable effect. If you have tests that show otherwise I would love to see them. And the bearings also seem to not last nearly as long. I'm not sure if this has to do with the quality of the bearings, the sealing being used, or the added movement you are referring to. Maybe a combination of them? And again, I think using the Keirin racers as an example just has no relevance. Of course they will use the system with the least friction, because the other factors don't matter to them. They are also not allowed to use any other system!

So let's get theoretical here for a minute. If you were to design the ultimate BB system, what would it be? Here is what I think:

Wider BB shell, maybe 90mm.
Slightly larger diameter BB shell.
Still use threaded BB shell, as pressed in bearings is just asking for trouble.
Use bearing similar to those used on a square taper BB, just bigger I.D. and O.D, using the same size balls and seals.
Use a spindle size similar to that of the external BBs.
I also like the idea of using a splined interface that is preloaded and then clamped to the spindle.

I think that is it!

Mark


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## aka brad (Dec 24, 2003)

DiDaDunlop said:


> Aren't HS cups made in the same way? Also supported outside the shell by an alu cup.
> 
> main difference in my opinion is that HS bearings have much better clamping and preloading system. Also HS bearings get a much bigger beating in my opinion. But because of the large cups and better preload system HS bearings are much more able to withstand the abuse.


 The loads on HS bearings are usually much greater that bb bearings; especially the lower bearing. Interesting I think the length of the head tube plays a big part in spreading out the forces; that and more and smaller bearings around a larger diameter spindle, aka steerer (ISIS showed the same does not work with a bb). One problem that is starting to crop up is on 29 er frame headset/tubes. Because by their nature they have shorter head tubes and longer forks then there 26 " brothers, the loads on the headsets are greater. 29ers are finding headset failure and ovalization is becoming a problem.


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## aka brad (Dec 24, 2003)

bikeny said:


> So let's get theoretical here for a minute. If you were to design the ultimate BB system, what would it be? Here is what I think:
> 
> Wider BB shell, maybe 90mm.
> Slightly larger diameter BB shell.
> ...


 So a wider ISIS bb with a larger shell and bigger bearings, such as the FSA Megatech standard but with a threaded cartridge. You could probably thread a BB30 shell and make a cartridge bb to fit,

Of course many would say the ultimate bb system already exsists; it's called square taper..


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## forwardcomponents (Dec 2, 2008)

aka brad said:


> The loads on HS bearings are usually much greater that bb bearings; especially the lower bearing. Interesting I think the length of the head tube plays a big part in spreading out the forces; that and more and smaller bearings around a larger diameter spindle, aka steerer (ISIS showed the same does not work with a bb). One problem that is starting to crop up is on 29 er frame headset/tubes. Because by their nature they have shorter head tubes and longer forks then there 26 " brothers, the loads on the headsets are greater. 29ers are finding headset failure and ovalization is becoming a problem.


Headset problems on 29ers may be due to the fact that they use longer fork legs. The fork acts a moment arm on the headtube. No surprise that you might find more ovalizing of the headtube with the increased leverage acting on it.


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## bikeny (Feb 26, 2004)

aka brad said:


> Of course many would say the ultimate bb system already exsists; it's called square taper..


I bet if you ask a bunch of downhillers and freeriders, you woudn't get that answer! But for basic cross country riding, may be right.


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## aka brad (Dec 24, 2003)

forwardcomponents said:


> Headset problems on 29ers may be due to the fact that they use longer fork legs. The fork acts a moment arm on the headtube. No surprise that you might find more ovalizing of the headtube with the increased leverage acting on it.


 I thought about that, but there are 140mm suspension forks on 26" wheel bikes and I haven't heard that they were causing the same level of headset problems as 29ers. Although 1.5 headsets are available, 1 1/8 is still remains standard.


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## aka brad (Dec 24, 2003)

bikeny said:


> I bet if you ask a bunch of downhillers and freeriders, you woudn't get that answer! But for basic cross country riding, may be right.


 So, since that vast majority of single speeders are not freeride/ downhillers, square taper does seem to be the standard for the Single Speed Forum.


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## Slurry (Dec 23, 2008)

External bbs are really easy to manufacture (compared to any other bb). Two identical aluminum cups that just have to be threaded different ways (compared to a cartridge bb). Kinda like threadless headsets vs threaded headsets, regardless of which you think is better, its just easier for manufacturers to make/use threadless headsets (which is why they've been the 'standard' for years).


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## bikeny (Feb 26, 2004)

Slurry said:


> External bbs are really easy to manufacture (compared to any other bb). Two identical aluminum cups that just have to be threaded different ways (compared to a cartridge bb). Kinda like threadless headsets vs threaded headsets, regardless of which you think is better, its just easier for manufacturers to make/use threadless headsets (which is why they've been the 'standard' for years).


Yeah, but threadless headesets are actually a superior design compared to a threaded headset.


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## bikeny (Feb 26, 2004)

aka brad said:


> So, since that vast majority of single speeders are not freeride/ downhillers, square taper does seem to be the standard for the Single Speed Forum.


You never mentioned that you were talking about BBs for singlespeeds, I thought you were just talking MTBs in general. Even among the SS riders on this forum, there are plenty of people that swear by each system, be it square taper, Octolink, ISIS, or external BB. I personally still use Octolink V1 on my singlespeed, and it has proven to be very reliable for me. I'm sure there will be others who have had bad experiences with it. In the end, choices are good, and just be happy you can still get quality square taper cranks and bottom brackets. You should actually be a happy camper, as there are more quality square taper offerings right now than there were 5 years ago, so obviously there are more people that think like you.

Mark


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## boomn (Jul 6, 2007)

aka brad said:


> The loads on HS bearings are usually much greater that bb bearings; especially the lower bearing. Interesting I think the length of the head tube plays a big part in spreading out the forces; that and more and smaller bearings around a larger diameter spindle, aka steerer (ISIS showed the same does not work with a bb). One problem that is starting to crop up is on 29 er frame headset/tubes. Because by their nature they have shorter head tubes and longer forks then there 26 " brothers, the loads on the headsets are greater. 29ers are finding headset failure and ovalization is becoming a problem.


Please don't throw around ridiculous exaggerations like that; silly biases get stuck in people's heads after it gets passed around second and third hand. It isn't a problem at all; probably happens just as often as it does with 26ers. To back up my retort, I just searched the 29er board for any instances of "ovalized" or "ovalization" and found *one* person who mentioned an ovalized headtube on a custom 29er frame over two years ago. Since then we have had more aggressive 29ers with longer forks becoming much more common and yet the problem hasn't grown. I have definitely heard of many people having their King's start to creak when they moved it to a rigid 29er, but that is related to a design weakness and the same people had zero problems after switching to a Cane Creek or something else

I'm not saying there isn't more stress on the average 29er headset, just saying it isn't a problem so please don't yell fire.

Now back to your regularly scheduled programming....


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## Schmucker (Aug 23, 2007)

forwardcomponents said:


> Headset problems on 29ers may be due to the fact that they use longer fork legs. The fork acts a moment arm on the headtube. No surprise that you might find more ovalizing of the headtube with the increased leverage acting on it.


And that coupled with the short headtubes only increases it further

Anyways... bigger spindle, bigger ID for the bearings, more bearings, more surface area support of the spindle. If the bearings are larger, they'll spin slower, thus wear less. Threading the cups into the frame and torque them to spec produces at most a teeny tiny bit of play completely unable to be felt by the rider. Perhaps if the threads were poorly manufactured and did not have a tight fit it could be an issue. But with the quantity of the threads and the pitch and considering the relatively low load of a cyclist it would basically completely transfer all force to the shell.


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## forwardcomponents (Dec 2, 2008)

Schmucker said:


> ...it would basically completely transfer all force to the shell.


Not quite all. The majority of the force on the bottom bracket is vertical. What is supporting vertical loads on a standard outboard bearing cup? A thin aluminum shell. It has to flex and deform under all that load, especially under off road conditions. The bearing races themselves are thin, so if their supporting shell is thin as well, then you are going to experience some deformation of the bearing geometry under severe vertical loading. The bearing as a whole is kept reasonably round by the large spindle that it is supporting, but it must be deforming more than a bearing that is supported within a thick bottom bracket shell. Again, I find it interesting that a Phil Wood outboard bottom bracket is made from stainless steel rather than aluminum. The material supporting the bearing looks to be about as thick as the aluminum found on most bearing cups, but is presumably far stronger. I doubt that Phil Wood's customers are willing to pay a premium for that weight penalty if there is no gain to be made in terms of performance and longevity.


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## aka brad (Dec 24, 2003)

boomn said:


> Please don't throw around ridiculous exaggerations like that; silly biases get stuck in people's heads after it gets passed around second and third hand. It isn't a problem at all; probably happens just as often as it does with 26ers. To back up my retort, I just searched the 29er board for any instances of "ovalized" or "ovalization" and found *one* person who mentioned an ovalized headtube on a custom 29er frame over two years ago. Since then we have had more aggressive 29ers with longer forks becoming much more common and yet the problem hasn't grown. I have definitely heard of many people having their King's start to creak when they moved it to a rigid 29er, but that is related to a design weakness and the same people had zero problems after switching to a Cane Creek or something else
> 
> I'm not saying there isn't more stress on the average 29er headset, just saying it isn't a problem so please don't yell fire.
> 
> Now back to your regularly scheduled programming....


 You are right; my bad. I was remembering the King Creaking Thread and had a senor moment. *To all reading this thread, 29ers do not have an issues with ovalising head tubes, some just don't play well with King headsets.* Now back to your regularly scheduled programming....


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## KeylessChuck (Apr 15, 2006)

I like most of the ideas for the ultimate bb thrown out there by Bikeny. As a singlespeeder, and freerider who has destroyed sq, taper, Isis and external bbs, I have always thought the ultimate would be an oversized bb shell and sqaure taper style bb (possibly splined). Sort of a cross between square taper and American/BMX.

I have a ss 29er with an eccentric bb that I'm dabbling in hardtail downhilling with, and after destroying the external bb bearings (can barely turn them, I think some of the balls are broken) I tried to come up with an American bb system that would fit in the eccentric shell and still take up chain slack. It's a full 3.25" wide (83mm outside to outside) and uses 6004 bearings.









So far so good. Obviously, the weight wouldn't sit well with most , but I'm liking the big ol' cheap, off the shelf bearings that probably won't have to be replaced for years. The other nice thing was to make the bb a press fit into the shell, so the shell wouldn't get ovalized (but that's another subject all together).


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## forwardcomponents (Dec 2, 2008)

KeylessChuck said:


> I like most of the ideas for the ultimate bb thrown out there by Bikeny. As a singlespeeder, and freerider who has destroyed sq, taper, Isis and external bbs, I have always thought the ultimate would be an oversized bb shell and sqaure taper style bb (possibly splined). Sort of a cross between square taper and American/BMX.
> 
> I have a ss 29er with an eccentric bb that I'm dabbling in hardtail downhilling with, and after destroying the external bb bearings (can barely turn them, I think some of the balls are broken) I tried to come up with an American bb system that would fit in the eccentric shell and still take up chain slack. It's a full 3.25" wide (83mm outside to outside) and uses 6004 bearings.
> 
> ...


That looks like a fairly indestructable bearing system and housing. You could probably get the weight down by removing more material from the center. The core is basically hollow, so it is probably lighter than it looks.


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## ShadowsCast (Mar 23, 2008)

j e SS e said:


> There needs to be some flex to help bear the load. Bridges flex. Skyscrapers flex. If they didn't they would fail prematurely Crank/BB/Spindles need to have some flex in there somewhere, too.


Terrible connection. Terrible logic.


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## KeylessChuck (Apr 15, 2006)

forwardcomponents said:


> That looks like a fairly indestructable bearing system and housing. You could probably get the weight down by removing more material from the center. The core is basically hollow, so it is probably lighter than it looks.


Yeah, I could have taken quite a bit more material off of this thing, but by the time I got to that phase, I was getting tired of standing at the mill (rotary table) and weight isn't a big concern with this bike.


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## bad mechanic (Jun 21, 2006)

I've used square taper, ISIS, Octalink, and now Octalink II in a mix of XC and DH. My favorite so far is Octalink II, and I plan to stay with it for one simple reason: the crank arm to spindle interface is by far the best of all the systems (excluding the new XTR system). It's simple, foolproof, and doesn't need adjustment and checking once set. When's the last time you heard of someone rounding out a Octalink II crank arm?

At first my cranks didn't spin as easily as with my cartridge BBs, but after switching to Enduro bearings they're nearly as good. I'll take that trade off for the more robust design.


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## Natedogz (Apr 4, 2008)

KeylessChuck said:


> I like most of the ideas for the ultimate bb thrown out there by Bikeny. As a singlespeeder, and freerider who has destroyed sq, taper, Isis and external bbs, I have always thought the ultimate would be an oversized bb shell and sqaure taper style bb (possibly splined). Sort of a cross between square taper and American/BMX.
> 
> I have a ss 29er with an eccentric bb that I'm dabbling in hardtail downhilling with, and after destroying the external bb bearings (can barely turn them, I think some of the balls are broken) I tried to come up with an American bb system that would fit in the eccentric shell and still take up chain slack. It's a full 3.25" wide (83mm outside to outside) and uses 6004 bearings.
> 
> So far so good. Obviously, the weight wouldn't sit well with most , but I'm liking the big ol' cheap, off the shelf bearings that probably won't have to be replaced for years. The other nice thing was to make the bb a press fit into the shell, so the shell wouldn't get ovalized (but that's another subject all together).


That looks sweet!


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## RSW42 (Aug 22, 2006)

DISCLAMER: The following opinion(s) are that of RSW42 and RSW42 alone, and do no reflect those of this network of it's affiliates.





External Bottom Brackets are monuments to the occasional stupidity of mankind.


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## thefuzzbl (Jul 5, 2006)

from a geared standpoint, all the cool shifting advances are coming in the external form. such as the new xt. also not all externals are created equally. ive had nothing but problems with race face and truvativ. i suspect that is because of the lack of bearing preloading. with the shimano and a few of the fsa cranks there is a separate preload adjustment. IVE only had external bb success stories when using that system. i believe companies like phil wood and chris king acknowledge that because they only support the shimano cranks. the only reason i sometimes use a bontrager(truvativ) crank is because i got it for free and working in a shop i can buy the bb's on closeout for around $2 a piece.


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## ISuckAtRiding (Jul 7, 2006)

Sorry, but you're a bit off.
External bearings use a larger diameter bearings, meaning that there are more balls, and more contact area. Also, the bearings are farther apart, giving more support. 
As an Engineer, external bearing cranks are a far superior concept, but they need a bit of work in the seal department. That's their downfall.
You will never catch me on square taper as i've destroyed more crank arms than i could count, even when i was 140lbs. And yes, they were properly torqued.
I'd rather replace a $20 set of bearings than a crank arm.


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## BEEZLEBOSS (Jun 16, 2009)

Well I like square taper for my Keirin track bike only because that is what it takes. but for all intensive purposes the external bb is fine TRUST ME! smooth as butter if installed correctly. Frame facing ECT.ECT. 
I'm a very large dude (300lbs 6.1) that can break any bike part you want
Bottom brackets are going to fail in time it's kinda the nature of the beast unless you have one that can be maintained in some sort of fashion. ( This is also why All Keirin NJS track bikes use loose ball because they can be maintained quickly. Do that with any other bottom bracket. Also nihon jitensha shikokoai (njs) is a sanctioning body to keep the bikes the same for betting purposes as the Japanese people bet well over a million Yen on these races per year. 

I've worked on bikes for most of my life and I can tell you the only parts i've seen that were worn out or broken are the one's that were on bikes that were A. doing things they weren't designed to do. Or B. poorly maintained. There are also manufacturer blunders no doubt but for the most part A&B are the main reasons these parts fail.


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## boomn (Jul 6, 2007)

thefuzzbl said:


> from a geared standpoint, all the cool shifting advances are coming in the external form. such as the new xt. also not all externals are created equally. ive had nothing but problems with race face and truvativ. i suspect that is because of the lack of bearing preloading. with the shimano and a few of the fsa cranks there is a separate preload adjustment. IVE only had external bb success stories when using that system. i believe companies like phil wood and chris king acknowledge that because they only support the shimano cranks. the only reason i sometimes use a bontrager(truvativ) crank is because i got it for free and working in a shop i can buy the bb's on closeout for around $2 a piece.


No, those fancy BB's support Race Face (and FSA) too. All three of those companies share the same BB specs. And I thought Race Face did have some sort of preload system through shimming it with different washers?


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## ShadowsCast (Mar 23, 2008)

BEEZLEBOSS said:


> Also nihon jitensha shikokoai (njs) is a sanctioning body to keep the bikes the same for betting purposes as the Japanese people bet well over a million Yen on these races per year.


1,000,000 yen = 10,000 dollars.


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## j e SS e (Dec 24, 2007)

ShadowsCast said:


> Terrible connection. Terrible logic.


Not really, the point is what doesn't bend will break. Bridges and bicycle drive trains are very similar in that they have forces exerted on them which have to be transferred. If the force is greater than what can be transferred and absorbed you have increased material fatigue and failure.

It's pretty basic, really.

How long to you think a rigid bike would hold up in a DH race?

Same principles apply, the energy has to go somewhere....in this case it's absorbed rather than sent through the bike and rider where it would inflict some damage.

Another oxymoron is that everyone wants stiffer frames and parts, but a smoother ride.

Problem is, all that impact energy has to go somewhere...and I see an awful lot of premature failures on these boards, especially frames.

I've explained my reasoning, can you explain yours, re: "terrible logic" ?


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## scooter2468 (Aug 5, 2008)

bikeny said:


> I think you have some good points and some that are not so good. First, on a mountainbike, you cannot use a square taper BB with loose bearings, no seals, and oil. It just won't last long. Sure, it will feel great for the first ride, but after that it will get gunked up. But it does bring up one of the main complaints about external BBs, namely the drag associated with the bearing and seals. This is definately noticable when spinning the cranks by hand, but I am not sure how much of a difference it actually makes will riding. I am not sure what you mean by less points of contact, I assume you mean less balls in the bearing? I don't think that is correct. I would think the external BB, because it uses larger I.D. and O.D. would have more balls, or at least larger balls which can support more load. As far as spindle wobble, I would think you would get less with the external BB system. Basically because the spindle is supported further out and because the spindle itself is much stiffer. Now I agree that if the BB shell was wider to the point that the bearings ended up in the same place as an external BB system, that would be better than everything else. I am not familiar with the BB30 system, maybe that is what it does.
> 
> I think the needs of Keirin racers are drastically different than that of MTB riders. A little extra drag is perfectly acceptable if it results in longer lasting bearings and a stiffer system.
> 
> Mark


Let's not also forget that just because keirin racers do something, it doesn't necessarily mean it's better. They are as subject to myth and tradition as anyone. Besides, even if replacing the grease with oil for one event does reduce drag, by how much? I bet not enough to be significant.


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## j e SS e (Dec 24, 2007)

aka brad said:


> I thought about that, but there are 140mm suspension forks on 26" wheel bikes and I haven't heard that they were causing the same level of headset problems as 29ers. Although 1.5 headsets are available, 1 1/8 is still remains standard.


That 140mm is absorbing most of the energy before it gets to the HS.....

Most 29ers are run either rigid or with relatively little travel, so more energy goes straight to the HS with less buffer, this is compounded by the fact that it is a longer lever.


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## gibbed (May 7, 2007)

One thing you may not have thought of. Because an external BB spindle is larger in diameter and stiffer, it will flex less under load. Because it flexes less, the bearing's inner races do not have to tolerate as much angular misalignment under load. This will lead to lower friction under load and better power transfer.

Even though the external BB has higher friction losses from the larger seals on the larger bearings, I feel the increase in stiffness is worth it for grinding out slow starts on a SS or taking big drops to flat.


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## bad mechanic (Jun 21, 2006)

j e SS e said:


> Especially with increasingly "laterally stiff, vertically compliant" frame designs.
> 
> Narrower and stiffer but lasts as long or longer ain't gonna happen.
> 
> The industry is loving it though, think how many more BB they sell now than when everything was square tapers that last forever.


You can go narrower and stiffer and still last as long provided it's properly engineered. The one thing narrower, stiffer, and long lasting might not be is lighter.

Square taper bottom brackets may have lasted a long time, but a lot more crank arms died with square taper than with external bottom brackets. I prefer replacing cheap bearings compared to expensive crank arms.


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## Roasted (Feb 8, 2009)

I have yet to understand how external bottom brackets are getting the rave they have. I've been on square tapers since the beginning of time. A while ago I acquired my first Octalink bike, which so far the stock Octalink cartridge that came with it already outlasted the square tapered replacement I recently put in my other bike. I definitely think I'll be sticking with Octalink for quite some time.

As it was said before, I too believe that BB30 will replace the external bottom brackets. However, I don't see BB30 taking off for quite some time. It's had some decent exposure yet not as many people have picked up on it as I thought they would by now.

I've ridden several external bikes and, yeah, they're nice... but them being nice doesn't seem to fill in the big shoe of why some people swear by them. Maybe I'm just naive, I just don't see the rush in it.

I didn't even have a reason to go from squared taper to octalink in the first place. It just so happened the bike I liked had one, however, I'm happy with my purchase. In the future, as I build onto this bike, if there ever comes a time where I'm in need of a new frame and BB30 is taking off with a solid reputation, I may jump on that bandwagon. Till then, I'll pass on the externals.


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## ISuckAtRiding (Jul 7, 2006)

bad mechanic said:


> You can go narrower and stiffer and still last as long provided it's properly engineered. The one thing narrower, stiffer, and long lasting might not be is lighter.
> 
> Square taper bottom brackets may have lasted a long time, but a lot more crank arms died with square taper than with external bottom brackets. I prefer replacing cheap bearings compared to expensive crank arms.


amen to that. i've replaced my own square taper crank arms well into the double digits (and yes, they were torqued properly).
Couldnt get them to not round out.


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## KeylessChuck (Apr 15, 2006)

gibbed said:


> One thing you may not have thought of. Because an external BB spindle is larger in diameter and stiffer, it will flex less under load. Because it flexes less, the bearing's inner races do not have to tolerate as much angular misalignment under load. This will lead to lower friction under load and better power transfer.
> 
> Even though the external BB has higher friction losses from the larger seals on the larger bearings, I feel the increase in stiffness is worth it for grinding out slow starts on a SS or taking big drops to flat.


See some of the original discussion above. It's not really the bearings that are in question, but the flimsy cups they ride in.


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## ShadowsCast (Mar 23, 2008)

j e SS e said:


> Not really, the point is what doesn't bend will break. Bridges and bicycle drive trains are very similar in that they have forces exerted on them which have to be transferred. If the force is greater than what can be transferred and absorbed you have increased material fatigue and failure.
> 
> It's pretty basic, really.
> 
> ...


Crank arms have a fatigue limit; crank arms that are flexing/bending/absorbing or whatever else you'd seem to think they do end up breaking. By your logic cranks would always be breaking at their least flexible, or thickest point. Time has shown that to be false. If you ever looked through pardo.net you would have seen nearly every time the crank broke at a thinner more flexible part, usually at the "vanity groove," a spot they had machined material away so the logos would not be rubbed off by use.










The only time something needs to bend to absorb the energy is when it isn't strong enough (or can't be made strong enough) to absorb it without bending. Given the relatively low forces cranks need to handle, in comparison with skyscrapers and bridges, they don't need to flex, and aren't built to flex; they are designed to transfer all the energy into the drive train and the frame without bending to dissipate it.


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## ShadowsCast (Mar 23, 2008)

Roasted said:


> I've ridden several external bikes and, yeah, they're nice... but them being nice doesn't seem to fill in the big shoe of why some people swear by them. Maybe I'm just naive, I just don't see the rush in it.


Some people swear by them because of the situations most everyone has agreed they excel. Downhill, large jumps, drops to flat... On square taper the spindle and interface become the weak link, not bearings, seals or longevity. With a spindle that large it is a lot stronger, and able to handle those kind of forces.

I agree with you that I can't believe BB30 hasn't at least spread a little bit more than it has... It seems like it's still just Cannondale's few high end models and that's it.


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## aka brad (Dec 24, 2003)

bikeny said:


> I am not sure what you mean by less points of contact, I assume you mean less balls in the bearing? I don't think that is correct. I would think the external BB, because it uses larger I.D. and O.D. would have more balls, or at least larger balls which can support more load. As far as spindle wobble, I would think you would get less with the external BB system. Basically because the spindle is supported further out and because the spindle itself is much stiffer.
> 
> Mark





aka Brad said:


> 1)I errored when I said fewer contact points. What I meant was the contact points were father apart.


Let me clarify my clarification. Most external BB have fewer (larger) bearing held in a cage, therefore, there are less bearings and less contact points. I don't know if this is true of Chris King, but it is true of Shimano and Race Face, with the Race Face DH BB having the full compliment of ball bearings; twice as many as their XC BB.



gibbed said:


> One thing you may not have thought of. Because an external BB spindle is larger in diameter and stiffer, it will flex less under load. Because it flexes less, the bearing's inner races do not have to tolerate as much angular misalignment under load. This will lead to lower friction under load and better power transfer


.

The problem is the external BB cups are much less support then the cartridge housed inside a BB shell. Therefore, the exterior BB will flex much more than the bearing being housed inside the BB shell. This causes more angular misalignment, which is why external BB bearings have such a short life; Chris King will only warranty their BB bearings for 5 years normal wear and tear not covered, and you have to grease them every 3 months or so; this compared to their headsets, which are warrantied for 10 years.


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## ISuckAtRiding (Jul 7, 2006)

aka brad said:


> Let me clarify my clarification. Most external BB have fewer (larger) bearing held in a cage, therefore, there are less bearings and less contact points. I don't know if this is true of Chris King, but it is true of Shimano and Race Face, with the Race Face DH BB having the full compliment of ball bearings; twice as many as their XC BB.
> 
> .
> 
> The problem is the external BB cups are much less support then the cartridge housed inside a BB shell. Therefore, the exterior BB will flex much more than the bearing being housed inside the BB shell. This causes more angular misalignment, which is why external BB bearings have such a short life; Chris King will only warranty their BB bearings for 5 years normal wear and tear not covered, and you have to grease them every 3 months or so; this compared to their headsets, which are warrantied for 10 years.


every external bearing bottom bracket i've worked on did not have a cage. They have sealed cartdrige bearings. The balls are nut to butt to eachother, meaning there are far more balls needed to fill the circumfrence of the bearing race as compared to any other type of bottom bracket. They probably have smaller balls, if anything, because the wall thickness of the bearing needs to be a bit more compact.


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## Miker J (Nov 4, 2003)

Octalink worked very well for me. Still does. Only problem I've had is the BB drive side loosening. Not many threads on that side. I must have a dozen of the BBs and 5 cranksets l still use. Got'm cheap when friends move onto "other" designs.

Still like square tapers for xc riding. Burned through my PW BB bearings in less than a year - go figure. My Shimano square tape is still going strong after years of abuse.


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## aka brad (Dec 24, 2003)

ISuckAtRiding said:


> every external bearing bottom bracket i've worked on did not have a cage. They have sealed cartdrige bearings. The balls are nut to butt to eachother, meaning there are far more balls needed to fill the circumfrence of the bearing race as compared to any other type of bottom bracket. They probably have smaller balls, if anything, because the wall thickness of the bearing needs to be a bit more compact.


 "The balls are nut to butt to eachother" ? I don't know what this means. Also the ball bearings are 35% larger than an ISIS internal BB. What make exterior BB did you work on. Most the sealed cartridge bearings I have seen are caged on the inside. Kinda looks like this.

Brad


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## ShadowsCast (Mar 23, 2008)

That means the balls are touching, with nothing between them.


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## bad mechanic (Jun 21, 2006)

aka brad said:


> Also the ball bearings are 35% larger than an ISIS internal BB.


From what I understand, this was the big problem with ISIS, that the bearings in it were too small, and therefore prone to failure. I saw this with my own eyes as my friends' ISIS bottom brackets kept failing. Generally, bigger bearings are a good thing as they handle large loads betters.

I have to wonder if part of the problem people are having with external bottom brackets isn't the fact they're not facing their bottom bracket shell before installation.

I also have a hard time believing there's any appreciable flex in an external BB's cups since they're of such a large diameter.


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## aka brad (Dec 24, 2003)

bad mechanic said:


> From what I understand, this was the big problem with ISIS, that the bearings in it were too small, and therefore prone to failure. I saw this with my own eyes as my friends' ISIS bottom brackets kept failing. Generally, bigger bearings are a good thing as they handle large loads betters.
> 
> I have to wonder if part of the problem people are having with external bottom brackets isn't the fact they're not facing their bottom bracket shell before installation.
> 
> I also have a hard time believing there's any appreciable flex in an external BB's cups since they're of such a large diameter.


 Again my take is that the bearings are hanging outside the BB shell. When pressures are exerted against the bearings, rather than being surrounded by a structural housing, they must rely on the rigidity of cups that are simply screwed into the shell. Therefore, rather than the fulcrum of the axle exerting its weight through the bearings and races that are contained by shell, the fulcrum becomes the interface between the cup and shell; specifically the interface between the bearing cup and shell. Even if the BB shell has been properly surfaced, it only means the bearings start out aligned. With an internal BB, the part most likely to flex is the crank arm, with an external BB the weakest point is the BB bearing cup.


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## bikeny (Feb 26, 2004)

forwardcomponents said:


> I am glad that somebody initiated this discussion. I have been thinking about this issue as well.
> 
> While looking at the Phil Wood site, I noticed something very interesting. As everyone knows, Phil Wood is noted for two things: very high quality bearings and seals, and square taper bottom brackets. What many people do not know is that Phil Wood also makes outboard bearing bottom brackets, as well as the bearings and seals for them.
> 
> ...


Where did you find any reference that the Phil cups are made of steel? I have been searching for info on this, but have not found any. The Phil Wood site does not have any info at all.

Mark

Edit: Nevermind, I found a bunch of store listings that say steel. Interesting that the Phil site has no info, though.


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## EBasil (Jan 30, 2004)

aka brad said:


> Again my take is that the bearings are hanging outside the BB shell. When pressures are exerted against the bearings, rather than being surrounded by a structural housing, they must rely on the rigidity of cups that are simply screwed into the shell. Therefore, rather than the fulcrum of the axle exerting its weight through the bearings and races that are contained by shell, the fulcrum becomes the interface between the cup and shell; specifically the interface between the bearing cup and shell. Even if the BB shell has been properly surfaced, it only means the bearings start out aligned. With an internal BB, the part most likely to flex is the crank arm, with an external BB the weakest point is the BB bearong cup.


With so much esoteric analysis, it seems that we Luddites have forgotten that external BB cranksets perform as apparently less flexy than internal sets, be they square taper or not. While it's true that many have ground through the cheapass bearings used in many ExBB cranksets, there's not an apparent issue of FLEX at the BB.

Either way, Shimano announced today that they're returning to BioPace, cantilever brakes and the UN-72, based on the illuminating exposure of their craven marketing, in this very thread. We've done our job fellas! :thumbsup:


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## boomn (Jul 6, 2007)

bikeny said:


> Where did you find any reference that the Phil cups are made of steel? I have been searching for info on this, but have not found any. The Phil Wood site does not have any info at all.
> 
> Mark
> 
> Edit: Nevermind, I found a bunch of store listings that say steel. Interesting that the Phil site has no info, though.


link 1
link 2


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## ISuckAtRiding (Jul 7, 2006)

EBasil said:


> With so much esoteric analysis, it seems that we Luddites have forgotten that external BB cranksets perform as apparently less flexy than internal sets, be they square taper or not. While it's true that many have ground through the cheapass bearings used in many ExBB cranksets, there's not an apparent issue of FLEX at the BB.
> 
> Either way, Shimano announced today that they're returning to BioPace, cantilever brakes and the UN-72, based on the illuminating exposure of their craven marketing, in this very thread. We've done our job fellas! :thumbsup:


i lol'ed a little.


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## aka brad (Dec 24, 2003)

EBasil said:


> With so much esoteric analysis, it seems that we Luddites have forgotten that external BB cranksets perform as apparently less flexy than internal sets, be they square taper or not. While it's true that many have ground through the cheapass bearings used in many ExBB cranksets, there's not an apparent issue of FLEX at the BB.
> 
> Either way, Shimano announced today that they're returning to BioPace, cantilever brakes and the UN-72, based on the illuminating exposure of their craven marketing, in this very thread. We've done our job fellas! :thumbsup:


 External Bottom Brackets do have less flex and stronger axles. The mis-alignment of the axle and bearing is not felt, it just decreases the life of the bearings. Square Taper BB are cheap, last 10 times longer and 90% of us riders wouldn't be able to tell the difference. I agree, it's all about marketing.


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## bad mechanic (Jun 21, 2006)

aka brad said:


> The mis-alignment of the axle and bearing is not felt, it just decreases the life of the bearings. Square Taper BB are cheap, last 10 times longer and 90% of us riders wouldn't be able to tell the difference. I agree, it's all about marketing.


- My external BB with properly faced BB shell and Enduro bearings is heading into it's second season on my primary ride (SS). I feel it might be an issue with cheap bearings, not an inherent system flaw.

- Like I said before, the bottom brackets might last longer, but square taper kills more crank arms, and I'd much rather kill bottom brackets than crank arm.

- I notice not having to constantly check my crank arms are tight. I enjoy having a crankset I simply don't have to worry about.


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## FruitaGuy (Jun 11, 2009)

bikeny said:


> So let's get theoretical here for a minute. If you were to design the ultimate BB system, what would it be? Here is what I think:
> 
> Wider BB shell, maybe 90mm.
> Slightly larger diameter BB shell.
> ...


Mark, you have some good points. So good in fact, that most of those ideas are in the works at a certain large bicycle manufacturer. I was able to see some "BB90" prototypes a few weeks ago. A 90mm wide shell and highly manipulated junction of the chainstay/seat tube/down tube area. Bearing replacement will be as easy as on an integrated headset. Saw a couple of cool designs for some of the new cranks coming out too, although I don't know about the model year release coming up.

For those discussing the differences between external bearings vs. cartridge type BB's, I think those who hit on the quality of the component are the most spot on. I've certainly trashed plenty of square taper, cartridge BB's in my time. And I've seen lot's of them as my years as a mechanic.

Finally, when it comes to Q-factor, it's a bigger picture than just a wider platform for support and control. Q-factor plays into shifting efficiency, lateral load on your chain and also, and sometimes most importantly, ergonomics when it comes to knee alignment. The latter is quite important for those who use clipless pedal systems, ride higher miles and/or have knee/hip problems.


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## aka brad (Dec 24, 2003)

bad mechanic said:


> - My external BB with properly faced BB shell and Enduro bearings is heading into it's second season on my primary ride (SS). I feel it might be an issue with cheap bearings, not an inherent system flaw.
> 
> - Like I said before, the bottom brackets might last longer, but square taper kills more crank arms, and I'd much rather kill bottom brackets than crank arm.
> 
> - I notice not having to constantly check my crank arms are tight. I enjoy having a crankset I simply don't have to worry about.


 I really have no argument with anything you say. Certainly if I had a problem with one type of a component I would look to another. OTOH, as I said before, for 90% of riders, Square Taper gives the same level of performance and lasts longer. I also like things that work. How long did your OEM bearings hold up? Or did you start off with Enduro bearings?


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