asking this general question primarily for a touring bike build.

Ive toured for about 25 years and do all my bike maintenance, regreasing hubs etc, repairs, but have only ridden on ball bearing bbs and square taper. With my square taper bikes Ive had very good experience. On my commuter, its UN-55 quality shimano bb lasted probably 12 years with probably 25000km on it, so I use that as a reference to excellent life, and I ride as soon as snow is gone and into December here in Montreal. A few years before I replaced it, a creak started, and I removed the bb, cleaned out the threads, put liberal amounts of grease on the threads, reinstalled and it stayed quiet for another few years.

with my project for a new touring bike, I see that there are reasonably priced 44/32/22 shimano deore 590 level cranks using hollowtech ll external bb's, but coming from my lack of experience with them, and conflicting experiences from other riders of how long they last, I'd like to get your experienced views on real life bearing life with them.

The lighter weight is nice, and I do understand how they are a lot easier to work on, but I could go either way.

I don't weigh much, 140lbs, so don't put out much torque, and my knees and legs prefer a faster cadence now at over 50 as when I was 25, so I imagine this helps with bb's just like it does with all drivetrain wear/life.
Are there big differences in ext bb life from one type of ext to another? Just as there is with varying qualities of square tapers? Like I mentioned, this Hollowtech ll is used on those trekking cranksets.

I've been hoping for a few years to do a much longer touring trip in Latin America, so I'm ok with the slightly heavier square taper if it really is more reliable and longer lasting. I do keep my drivetrain clean, although from inexperience, I don't know how much this plays into ext bb's lifespan of stuff getting in, and a trip in Latin America is going to be more gungy overall than my city riding here.

thanks

I'd appreciate your experience and insights

I got 24,000km out of my first external bearing bottom bracket before it got a little rough; but it spent nearly its entire life with too much preload (FSA made some carbon cranks too narrow for the "correct" bottom brackets which come in several widths). For over half that time I weighed under 140 pounds, but was 205 at the beginning.

I don't think that was out of line with my last square taper bottom bracket, but wasn't using a bike computer at that time.

Some external bearing bottom brackets are sensitive to how the shell has been faced, wearing quickly when the left and right sides aren't parallel and co-axial.

I have Shimano BB6700 (Ultegra level) HTII bottom brackets on two bikes with over 10,000 miles (>16,000 km) on each and they are still in perfect shape. So, I don't know how long they are going to last but so far longevity has been absolutely no problem.

This isn't to say that external BBs don't or can't last, but my long term experience is that good quality classic cup/spindle BBs outlast their modern replacements by a large margin. It used to be rare to replace BBs or bearings due to wear, which has become a more common repair with the advent of new and improved BBs.

I suspect that the key difference is rigidity. Bearings are very sensitive to misalignment, and flex in many of the current BBs may be costing bearing life.

OTOH - modern BB systems are much lighter, and that , even at the cost of shorter life may be worth it as a trade off.

I think the emphasis here has to be on "good quality", say Campy or higher line Shimano cup-and-cone bottom bracket spindles and cups. Cheap spindles like some of the entry level SR and Suguino bb's did pit rather quickly even if lubed and adjusted properly.

If you're happy after all these years with your current set up OP, I'd just stick with it.

The alignment aspect is something I've read about and can see that it makes sense. Last summer I was on a week long tour and meet a guy who was touring and told me about his bad experiences with his bikes external bb. If I recall he had had them changed four times, and each time not losing more than something like 2 or 3000kms, at different shops. It didn't make any sense to me, but the possibility of poor facing and alignment could very well been the factor here, he was a tall guy who looked strong so this could have been a factor that played a part.
I will very much keep this in mind and make sure proper facing is done it I end up going with external.

As you say about it being lighter--I'm glad to hear these mentioned lifespans that are good. As for the weight, with fully loaded touring, I learned a long time ago to be careful of total weight, and so would welcome a reasonably priced crankset like that deore trekking one that will be lighter than square taper.

Yes. I'm comparing A and B line parts for both. Otherwise it's meaningless.

Like I said, I can very much see from my experience that a good quality square taper like a un55 in a good frame, properly installed, will most likely be forgotten for a long time, and that's great.
That said, I like the idea of learning more about external bb's, as they certainly are on lots of bikes, and I don't want to unaware of different external bb's if they indeed can have good longevity.
I really enjoy working on bikes too, so also want to learn more about what I don't know.

Sure, I can totally dig that.

Re quality/levels of external bb, for 48/36/26 44/32/22 type cranks, are there external bb types or models that are more recommended, less recommended?
I'm sorry but I'm still not familiar with the various ext bb, just somewhat familiar with haven seen some of the names like hollowtech.

Excuse the question, but how does one affect chainline with ext bb's? I know with square taper you choose the right length spindle, but how does one adjust it ext, I'm specifically thinking of mtn crank going onto a frame and needing a different chainline.
Is this why a crankset like that deore 44/32/22 is always sold with the bb included, so that the mtn bike chainline that is wider than a road chainline is going to be properly set up with that given bb?

One thing not mentioned is that the Shimano external BB's can be re-lubed. After removing the plastic sleeve just use a blade to pry off the seal and the bearings can be flushed and greased. Choose your maintenance intervals but I think even in the worst conditions every 5k miles would be safe and you may be OK with every 10k miles or more.

My external bb (ultegra) on my everything bike had about 5000km on it before it was run over, its now on my dedicated commuter (80s steel mtb dropbar conversion) and still going strong, neither of these bikes had the bb shell faced and personally I dont think its important the cups will follow the threads regardless, prior to that I ran cartridge style shimano bb's I've had to replace 2 of these(all weather cyclist) but I cant tell you the kms. If given the choice I would always plumb for the external bearing type they are hell cheap,durable and easy to install.

Square tapper is as good as it gets, unfortunately. I'm not a mechanical engineer, but ride a lot and service bikes and am not happy with any BB solution so far. However, the least problematic is the old square tapper. Lasts long and performs OK. If not racing, it is more than good enough. If longetivity and ease of maintenance are a priority (as well as low price), I'd recommend square tapper.

Thanks for mentioning that, I have seen a YouTube video of that, but do not recall which specific brand type of bb it was, but given my experience with keeping ball and cons hubs regularly regressed, this is something I would do.

Bringing up ball bearing hubs touches on quality connected with longer life. I've certainly noticed over 30 years how better quality hubs last longer, adjust better and have better seals to keep grease cleaner longer. I assume ext bb's are no different, just like square taper bb.

If I wanted a bomb proof bottom bracket for touring in parts unknown, I would get the SKF bearing bottom bracket square taper. It comes with a 10 year warranty. Its a cartridge type, so no fuss.

My experience with external BB has been dismal at best. I used a GXP BB on my daily commuter and the bearings last about a year if I am lucky and I even faced the BB shell. With that said, you can't beat the simplicity of installing or removing of this style of BB and the weight differences makes it worth while. Maybe the Chris King external bearings are better?

My commuter has over 20K miles on an ultegra external with maintenance basically every couple years pull the crank and clean things up down there with a rag. While not "hard core" I have ridden it in plenty of weather.
I've also had very good luck with UN-54/55 cartridges giving good service.

My concern on a tour would be the availability of spares; I would imagine that the square taper type with its long history and common use would be easier to source away from home.

interesting comments, this touches on cost, and I'm not keen on getting a $120 or more skf bearing when my real life experience has shown that a $40 shimano un55 gets great life, but this also touches on cost thing--the fact that I can get an entire Deore trekking type crank with the chainring sizes I know from experience I want plus the bb for about 100 bucks is a good deal. I could put my old mtn crank and un55 from my old mtn bike over to a new frame (Surly Troll type sort of thing) or just use the crank and put in a new bb, but for 100 bucks give or take, I can leave my mtn bike as is and still use it as the visually battered commuter it is, and I do have confidence in Shimano mid range stuff like Deore being a good bang for buck, especially for a touring application where I dont want to have too too much money in the bike in case of unlikely circumstances (theft, whatever)--yet still have perfectly well performing parts, ie "its the trip, not the fancy doodads" attitude.

thanks for your GXP experience. Being new to this, this is the sort of real life experience I would like to see here. Is your bb situation unique? Who knows, but I will certainly remember GXP with a bit of reserve now.

Would like to say thanks for all the comments.
re availability and durability, I would not be away for a year or something, probably a month or two tops, so within reason I wouldn't have durability concerns, and if I were to go ext bb, it would easy to put in new bearings before the trip, or to simply regrease. I would also want to get significant riding time in on the bike before a trip, and also to get experience doing work on the bb, plus I imagine taking along a spare set of bearings is not an issue, and would be rather light if real concerns about availability were there--this touches on another reason for sticking with mid level shimano stuff, in general, its found in most places, or at least the chances of finding a place with it nearby is a lot better than fancier stuff. Comes back to the "bang for buck" aspect, as availability and commonality is a factor here too.

Unless you are going to tour extensively "back of beyond", I wouldn't worry about bottom bracket failure. In the unlikely event of failure, any half decent bike shop will have Shimano Hollowtech II replacement bottom brackets at reasonable cost and installation is a matter of a few minutes. Don't use the GPX experience as a guide to external bottom brackets in general. Shimano's, particularly 105 level and above, are fine.

The chainline on HTII cranks is defined by the spindle built into the drive-side crank arm and is fixed. The bottom bracket is not a factor.

Old Grease guard Square taper BB seems to Keep working,

My Touring Rig was Built in Eugene, of 89~90 Burly tandem parts Its Oversize bearings

normally went in Auto clutch Throw-outs so the Bike is a low stress app.

(+ It's got a whole lot of grease between the bearings as the shell has no holes in it. other than the Zirk and the bearings in the ends of the Tube. )


But if the parts have to be the latest offering, 11 speed Etc. , External BB is what you get.. its part of the package.

your first comments are pretty much how I look at it, tks for the comments.
re chainline, afterwards I thought about it and of course the spindle is fixed, so the positioning of the cranks is determined by that. Thanks for clearing that up.

From experience I know I will go with a 44/32/22, taking into account regular touring load+plus possible extra weight of supplementary water, food if the situation requires it. If you have to be safe and carry lets say 10l of water, thats another 22.5lbs just there, so lower gearing is always going to be appreciated. Also, in Latin America gradients can be pretty darn steep. I've toured a fair amount and know what my old knees need for a given terrain/bike weight.

as I've said bob, I've had great experience with sq taper. I forgot to mention before, but I will be using 9 speed, and when I started looking at crank options--use my present mtn crank off the commuter (might have to replace a ring or two) , pick up a used mtn crank sq taper, it all comes down to options of cost, and seeing the 9 speed trekking deore crankset with bb for about 100 bucks is a good deal---but really I started the thread to get opinions on real world life of outboard stuff, as I've never owned a bike with it, haven't worked on it, and only have one friend who has a bike with it and she doesnt ride it that much, so have never looked at it or taken it apart.

Plus, I've heard opinions going both ways in terms of longevity, so didn't really know what to think.

re 9 speed, I've toured on 6, 7, 8, 9 speed, and I would go 10 for this bike, but given where I want to go, I figure sticking with 9 would be still best for any parts issues that could come up. I've lived and travelled in Latin America a bit, and my friends in Costa Rica who do mtn biking tell me that 10 stuff is avail there, but I still like the idea of sticking with 9, as I would love to travel in countries that may not have the same options as CR.
Same reason I want to stick with 26in wheels, a bit stronger also and I don't want to get into the 700 or 29er issues when travelling in Latin America, and can live with 26 easily as I continue to use it on my old mtn bike.

I do however want to use dropbars and mech disc brakes. Drops simply because they are still the most comfortable for me, and mech discs just because of being on dirt, rain, mud etc for rims, and I've never had a disc bike, so figure what the hell, try it out. Folks have been touring with them out in the boonies now for years, its not much of a gamble, lots of solid use touring.

so Im thinking of going wild, ext bb and discs! ;-)

I appreciate your comments though, thanks.

Shimano external BB (Hollowtech II) are probably the gold standard for reliability in BBs. Other press-fit designs have a significantly worse reputation, but when it comes to HT2 that's basically as bulletproof as you're ever going to get. I'll wager the average HT2 BB could go 5-10 years without the slightest bit of maintenance.