BB-UN55 vs BB-UN300; which is the better square taper bottom bracket?

In this video I’m going to delve into the BB-UN55 and what makes it one of the top choices if you’re looking for a new square taper bottom bracket.
And I’m also going to cover why, in a BB-UN55 vs BB-UN300 shoutout, the BB-UN55 comes out on top.
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[@kan708]

Thank you for producing this insightful and informative video.

[@xKillYourTVx]

Just got a brand new bb55 for 12$ ! Thanks for the video that lead me to it. Let's see how it is.

[@Autonomous_17]

Back in the olden days when I started biking at a young age, I would save up and upgrade components as I could but now that I can afford to own bikes and restore them I just go with whatever the bike originally had, obviously while trying to find the best option but I like to keep them as period correct as I can

[@stephenk0nig252]

I think you talk a lot of sense here. Totally agree.

[@Gromitdog1]

Shimano's cartridge bottom bracket was revolutionary, taking a component that required frequent servicing to a maintenance free reliable component that so long as you didn't blast water and degreaser into the seal and wash away the grease would last a very long time. Too bad nothing higher than the UN26 is readily available. The UN72 was amazing and silky smooth.

[@ianmangham4570]

I still use shimano sealed square taper, way stronger than external crap

[@SplendorSolis]

Suntour had the VX line of sealed bottom brackets in the early 80s.

[@valixt]

230903: about "Square Taper Bottom brackets need to go some day": Currently almost all ebikes I saw under 2000$ used this type of BB's because it is easier to install the cadence sensor for pedal assist on them.

[@restorationdotbike]

I feel that for something to be a bicycle, it needs to be human powered, so I never took e-bikes into consideration. You're right of course though. I feel the main reason square tapers are used on e-bikes has to do with a lower price, and things like stiffness and weight are non-issues.

[@kalveend]

thank you

[@DoNNiEdx77]

it's a pity that the BB-UN55 is now discontinued.

[@restorationdotbike]

Indeed it is

[@IronHorsey3]

@@restorationdotbike - based on your rec, I found a brand new BB UN-55 to replace an old UN-52 in a Trek 5200. Thanks for the video and am curious about more details on the UN-55's superiority over the readily available UN-300.

[@charlesfosterkane8034]

I have a BB-UN72 on my Surly Crosscheck

[@AB-eg3ei]

I have never opened a BB-UN55 but I´m pretty sure that internally it is a "cup and cone" type bearing. The correct technical description would be, that it has two angular contact bearings where the inner race is directly ground into the spindle, the outer races are fitted into the cartridge shell. The BB-UN300 is completely different. Two radial roller bearings ("industrial bearings") are pressed onto the spindle. One advantage of the first type is, that the balls are bigger. Another difference is that angular contact bearings can be fitted with quite some preload. Radial roller bearings can only be preloaded very lightly. You can feel that preload when you take a new UN55 out of the box, it`s smooth but a little bit stiff. What happens when you start riding is that the bearings will "set", it basically means that races and balls will grind against each other on a microscopic level until they fit perfectly, the UN55 will loose the initial stiffness within a couple of hundred kms and will typically last a very long time without any service. With the BB-UN300 I can´t tell. This type of construction is usually found on cheaper square taper bb. The fitting is probably not as tight, it can not be preloaded the same way, maybe the components are of a lesser quality, who knows? There are high quality versions of this type around (phil wood) as noted in the video and the "industrial bearings" can be replaced. But again these types also rely on a tight press fit between the bearings and the spindle, so for the average user it is not that easy to replace the bearings. Hollowtech 2 is much simpler to service in this regard, but comes with it´s own set of problems. HT2 relies on the frames BB shell for the alignment of the bearings. If the frame is not perfect, you might get problems with creaking and/or rapid wear of the bearings, a problem that was pretty much unheard of with the high quality shimano cartridge type BBs.

[@restorationdotbike]

In general, and this is based in part on personal experience, I would argue that "older is better". What I've seen is that same-type technology today versus decades ago is using cheaper materials. Technology has reached a level of minuteness and complexity which increases changes of failure. Technology has become non-mechanical and depends on batteries and/or software with a short lfiespan. And the ability to service products and replace components play second-fiddle to marketing and sales or don't play any role at all. Assuming that I'm correct the chances of the BB-UN300 being of equal or higher quality than the BB-UN55 is almost impossible. But you display more knowledge about bottom brackets than me so who knows.

[@AB-eg3ei]

@@restorationdotbike Yeah, sorry, I got a little bit carried away in my comment, but that is exactly what I was trying to say. If you look into the construction, these older style shimano components often scream "build to last". In the case of the UN55 it´s about how these angular contact bearings are neatly fitted into a comparably massive shell with very tight tolerances. The change from longlasting components to throwaway stuff is even more visible, if you look into shifters. There are some very nice videos of "atboy", who takes apart a lot of old tech. If you see the insights of a M739 XT shifter, these things are built like a tank. That kind of build quality is just not available anymore, sad... For BBs you can still buy the BB-UN26. It has the same basic construction like the UN55, only the cartridge is made of steel instead of aluminium, what makes it a bit heavier, but the quality should be there.

[@tocaamerillo431]

About UN300's construction being similar to cheaper brands' BBs, I find it interesting that UN300's bearings appear to be significantly narrower than in said cheaper products. Would that imply smaller bearing balls inside? The bearings being more delicate in general?

[@AB-eg3ei]

@@tocaamerillo431 Yes, a narrower bearing has smaller balls, but in terms of lifespan whats more important is a) the fit and finish b) the quality of the races and balls and most important lubrication and cleanliness. If you get water and dirt inside a ball bearing it will fail very fast, no matter the quality

[@V8_screw_electric_cars]

I've had UN 300 fail very quickly as water got into it and cartridge bearing was all rusty inside, those fancy seals are useless, at least the one the non drive side. I used to have old bike with plastic cup shimano bottom bracket and that one lasted a long time I think it was some cheapest model that they used to have. The UN 300 isn't even that cheap I wouldn't recommend unless you live in some nice place not a hellhole with 6 months of winter like I do.

[@MarshWaha]

Sucks the Shimano BB-UN55 is discontinued. It’s way, way better! I freaking love this Bottom Bracket it rocks. Very disappointed that square tapered BB’s are not as in demand, this model is the best on the market now it’s rare and hard to find.

[@lereveure]

Thanks for the video, but didn't see a lot of +s and -s comparing the two.. maybe next time outline those :)

[@peterpipe9015]

I just put a fsa powerpro bottom bracket in a mountain bike , i should of got a shimano but the sizes were limited

[@restorationdotbike]

Unfortunately they are indeed getting more rare with each passing day.

[@rangersmith4652]

Would a UN55 serve as a drop-in replacement for a Tange Seike unit of the same spec? I can't see why it would not, but I can't find confirmation anywhere.

[@restorationdotbike]

"same spec" = yes

[@47f0]

Does anyone know what the hard black plastic ring on the drive side spindle is on the UN 300? I see the same one in this video, so I wondered what the purpose of this odd ring is sitting in the middle of the spindle is for.

[@petesmitt]

The crankset butts up against it; basically for correct chain-line position.

[@paulywogtheburnin8r364]

Too bad they stopped making the un55 and now they are in limited supply, the un300 seems fine, but I’ve been reading about how they are more prone to failure. I guess Shimano is just shifting away from square taper. There are options from other brands which are affordable and seem solid such as the Tange LN-3922 and 3912 as well as the IRD QB55 which seem solid. IMO any sealed bb will be solid since loose ball/cage bearing bbs just don’t keep out the water great.

[@tocaamerillo431]

BB-UN26 has failed on my bike after a couple years, so I'm now looking for a replacement... What's left of Shimano's square taper lineup is frankly not very encouraging. I've narrowed my choice to be between UN300 and Neco B920AL (I don't care much for it being aluminium, but it comes with extra seals in the cups compared to steel Neco models). I'm veering towards Neco because of... well, just compare the sizes of the bearings! I haven't seen UN300 in person, but on all the photos I can see its bearings appear to be maybe 60-70% width of the bearings you can find in cheaper brand BBs. I understand this might not be telling the whole story, but surely for the part that has to bear such stresses size does matter.

[@restorationdotbike]

I've now used the BB for about 2 years on my daily driver without any issues except a cosmetic one of rust on the spindle. I do take very good care of my bikes, so I'm maybe not really representative of the average user. As far as bearing life is concerned. It's highly dependant not on frequency of use, but in what conditions the bearings are used. In general sealed bearings can last for years or even decades, unless their seals are compromised and dirt, grit and moisture gets to the bearings. I've known people who've ruined their very expensive, very large, high quality bearings, after a single very muddy, very wet ride. Riding in dry conditions simply makes an enormous difference versus riding in wet conditions.

[@coldcrush1]

I'm rebuilding a Cannondale R400. Would this bottom bracket work?

[@restorationdotbike]

yes

[@francissiu9549]

Have you tried the Token one?

[@restorationdotbike]

Not for lack of trying. But unfortunately it took ages to arrive using Ebay and was send back because I failed to pick it up from the post office :( But I have to say it was my first pick over the BB-UN55 initially.

[@markjmaxwell9819]

The BB-UN300 is pretty hard to beat for twenty dollars. My last bike had a non sealed caged bearing bottom bracket the BB-UN300 is a huge step up from my old bottom bracket... I hope my new bike has a BB-UN300 or a Hollowtech 2 bottom bracket...

[@arncj18]

got a 51, 122mm -68mm, ha!

[@fattahyourkaef7500]

bb shimano un-300 or bb neco b910? because bb shimano via japan is hard to find for size 122mm, help

[@restorationdotbike]

I'd settle for the Neco

[@magnumllama400]

Where did you find the neco one?

[@Goodman-4525]

Why exactly is the 300 inferior then? You didn't say anything apart from the fact that it's placed at a lower level than the 55. What technical specification led you to this conclusion?

[@restorationdotbike]

Shimano used to make the bottom bracket equivalent of a Volkswagen, Skoda, Audi, and Mercedes. With the BB-UN55 being a Mercedes and the BB-UN300 a Volkswagon. Shimano now only makes Volkswagons. There's no longer a large enough demand for Mercedes' equivalent of square taper bottom brackets for them to make them. In general a Volkswagon is deemed inferior to Mercedes.

[@DoNNiEdx77]

For example, the BB-UN 300 has smaller bearings (about half the size of the 55) and they are more "exposed", because the non-drive side seals are part of the cup (not the body) and it does not have a one-piece body with both bearings encapsulated inside of it.

[@DeiviZZZ]

hi, it would be awesome if you did a disassembly of both, and compared internal parts.

[@escgoogle3865]

Sadness the un55 no longer made. Price performance amazing. My oldest BB is an SKF but I don't ride that one in the rain. Hollow tech 2 is a no for me unless on a travel folder.

[@wildbikerbill6530]

HollowTech II is a No because?

[@escgoogle3865]

In yucky conditions HollowTech II stats: #1 south America averaging 55-65mi a day with four bags. ~4000mi. #2 Baja and the American SW + two immersions ~3000mi. My commuter un-55's last 10k-15kmiles. Note: With HollowTech It is incredibility easy to pull the cranks arms and/or replace the BB.

[@wildbikerbill6530]

@@escgoogle3865Thanks, much appreciated.

[@guitarfreakfalko]

My BB-UN300 failed after 4 month and about 1000km, but i believe i may have overtightened the nondriveside cup. If you find that after tightening the nondriveside cup the axle is difficult to turn, you might want to backup like an eighth of a turn until the axle is turning freely again.

[@restorationdotbike]

It's my experience you cannot tighten a non-drive side cup in such a matter that it impact the rotation of the BB. Just as you cannot tighten a skewer in such a way that it impact the rotation of the bearings in the hub. If my assumption is true it means something else was is going on with your BB.

[@guitarfreakfalko]

@@restorationdotbike Metal is hard but it can indeed move a little. I found that tightening a skewer does impact the bearing play, espacialy with aluminum axles.

[@V8_screw_electric_cars]

Mine failed too the bearing on the non drive side was completely rusted even despite those seals, very strange, in fact it was worse than unsealed tange bottom bracket that I used to have that had cartridge bearings exposed.

[@JohnDoe-zb7dz]

Another prominent bike mechanic says NO grease on the square tapers. Clean them very well and strip any signs of anything on them. So which is it?

[@restorationdotbike]

Do you have a URL I can look at? Would be very interested to learn why NOT to use the number one method in reducing risk of seized components because of corrosion.

[@JohnDoe-zb7dz]

@@restorationdotbike White Industries told me to stop this practice. I ruined my first Square Taper cranks from them because no matter how tight or how much blue lock tight on the threads they were working loose. The new set started walking as well. That's when they discovered I was using grease. They told me to clean the tapers very well. Boom. No problems now whats so ever. Typically you grease things like this but just not square taper parts. You can ruin a set of square taper cranks very easy.

[@V8_screw_electric_cars]

My crank was creaking like mad until I put some grease on it, I'd definitely put grease.

[@JohnDoe-zb7dz]

@@V8_screw_electric_cars I regrettably tried the same. Be prepared to replace them.

[@V8_screw_electric_cars]

@@JohnDoe-zb7dz Why would I, you always should put grease wherever metal meets metal, same with stem in steerer tube otherwise it will creak to no end.

[@cristiansantacruz9120]

bb-un100 and bb-un300, they were bad products for me.

[@Andfox13]

Shimano BB-UN55 or Neco B920HAL, which is better?

[@restorationdotbike]

I have a Neco lying around which I never used because I accidentally bought the incorrect spindle length for the particular bike it was meant for. The reason I bought a Neco was because it's readily available, came with an aluminium fixing cup, and seemed more premium compared to the BB-UN300. But that's as far as my experience goes. That being said the BB-UN55 was installed by many brands on many high-end bikes at the time. I doubt the Neco has this track record.

[@magnumllama400]

Where can I buy neco?

[@charlestaylor6898]

In my experience. UN 55 30000 miles UN300 5000 miles both on fixed wheel bike. No comparison.

[@restorationdotbike]

30000 miles, talk about a long term review ;)

[@hade8194]

Fett auf die vierkant aufnahme ist ganz schlecht. Alukurbeln können brechen da sich das fett in microrisse drückt

[@xKillYourTVx]

also einfach ohne alles den Kurbelarm anschrauben?

[@randy1817]

The UN-300 BBs are flat out junk!! I got one the other week. It was very rough right out of the box, I returned it asap!!

[@restorationdotbike]

My personal experience is a bit more nuanced than yours, but less than average as well for the UN-300. It hasn't survived a single season without keeping its smoothness.

[@ericdavis7532]

The bb un300 only has one side with a flange, looks like shit