Building up a cross check as a commuter. Want to buy a BB that'll last me for a long time and possibly is serviceable?

I've read a few things.

1. Buy an expensive external BB that's fully serviceable aka King
2. Buy a much cheaper Shimano XT BB and just replace it in a dozen years or so.

Anybody have opinions for external vs. internal BB bearings on a commuter? Technically the external ones are "tougher" while being lighter due to using bigger bearings and a hollow shaft, but are they good for long term? Do I really need external ones? All of my other bikes have internal bearings on the BB.

What is your goal? King might last you longer than shimano, but you will pay an order of magnitude more. As long as you're not buying a $5 Chinese/used ebay special (or powerspline) then with respect to intenal vs external, take your pick. Internal sealed square taper setups can save you more money relative to an external bearing setup. I've used several internal and external bb setups and have never had issues with any.

The cheapest, most durable setup will be serviceable, non-sealed bearing units. Notice I said cheapest and most durable. Otherwise, just buy what you can afford, build it, and ride it. If the winter kills your bb then buy a new one or overhaul it if possible.

If you want cheap and durable get a square taper bottom bracket. Even the lower end ones will last forever. A Shimano UN55 can be bought for about 20 bucks and will last decades. I'm pretty sure that's what I have on my 1x1 and that thing has seen a lot of miles and crappy conditions. If you want something fancier, buy a Phil Wood and then you can even replace the bearings in the unlikely event they fail (the Phil Wood on my Fatback has been on for eight years and thousands of miles in conditions including mud, slush, even volcanic ash mixed with the snow. Thing still spins like the first day)

External BB usually fail earlier than square taper. But they give you the option to use modern cranks. The selection for square taper is getting limited.

There exists no dataset to back that claim up. The rest is solid advice.

You need to decide what crank you are going to use before the BB, as the crank will decide which BB type your going to use.

For serviceability vs longevity, how may XT BB's can you buy for the price of one CK? also if a Shimano MTB HT2 crank, they often come shipped with a BB included.

While no, there is no scientific study to back it up, my personal experience (and that of everybody I know) is my dataset. Couple that with the fact that people regularly service and replace external BB while servicing and replacing internal BBs used to be pretty much unheard of and I think my comment is substantiated. Mind you, I should probably clarify I'm talking about threaded bottom brackets. Press fit one's are all over the place right now in terms of durability.

My own personal experience, as well as that of two buddies, one of whom races, is completely opposite of yours (with exception, as mentioned, to powerspline) in that no problems have surfaced with either external or interal BBs. That's the problem with anecdote, the sample size is 1 and often contradicted by some other bloke's experience. Ie it's useless as an extrapolated statistic.

Some brands of sealed square taper BBs appear to use stock bearings. For example IRD.

So, in theory, you could rebuild your BB with new cartridge bearings. In reality, it probably won't be much of a savings, unless you are using something like French or Swiss bottom brackets.

Explain why a cottage industry of external bottom bracket bearing replacement sprouted as soon as external bottom brackets became popular. That isn't anecdotal, that is a fact. While external bottom brackets have improved a lot, the fact remains that a low end internal BB will last 20+ years with no maintenance. I'd like to see a external BB do that.

Okay...I will pose the same question: what can you offer to substantiate this claim? All I'm reading is anecdote and opinion. I am in agreement with most of what you are saying but let's be real, it's all just hearsay.

So you can't explain why a cottage industry of bearing replacement suppliers developed. Nor can you explain why CK provides replaceable bearings. Why Phil Wood does the same. But hey, since I already told you that there isn't a scientific study about it you keep asking for it.

For the OP if they want low maintenance and durability go with square taper. If they don't want square taper, use whatever comes with the cranks they buy and replace as needed with the cheapest option available. One nice thing about external BB is that they are easy to replace and cheap.

I didn't ask for a study, I asked for a substantiation. You answered with opinion.

I will not pretend to analyze the market forces which motivated your cottage industry - you are more then welcome to school me though. My area of expertise is medical biology, perhaps yours is economics.

I'm unclear why this is so upsetting to you; it's your opinion that internal BBs last longer than external. That's great, but it's an opinion, and your opinion is not a rationally verifiable claim for anyone on this forum. If it was then we could figure the statistics and determine the logical answer, but this is not the case.

Again, I agree with most of what you are saying; let's call a spade a spade here. Ie, an opinion is an opinion.

Whatever. You want to ignore information, go to town.

What information? I keep asking you - feel free to answer with said information.

Platique - C4 or fertilizer and Diesel ?


Nicest BB I had was a square taper the bearing cartridge was behind Shaft packing in each Cup

so the sealed bearings were behind another set of seals .

But this was the German Sachs , they were Bought out By Sram , and the company No Longer exists .

WTB grease Guard is what I Fit as a Replacement for the 1st UN xx that needed replacement

Sun Tour made them, theyre Gone Too.

Actually the externals use smaller bearings , but there are More of them surrounding the big 24mm tube spindle.

Starting with a clean sheet of paper?

I'd begin with the gearing and decide on whether 1x, 2x or 3x crankset. Is this an internal gear hub setup in the rear, or something else exotic versus just a derailleur system? Then select the BCD that gives you the chainring options that you need.

Now to the rear, assuming a derailleur. Then choose the cassette that sets the upper and lower GIs that you'll need for your commute. Iterate to make sure that the shifting combinations make sense.

Now, shop for cranksets that meet your budget and whatever you decided for requirements. The crankset will inform your bottom bracket bearing choice. There's likely no wrong answer, is there?

There are no guarantees that the bike or you will still be alive in a dozen years, or that you'll still be digging this bike by then.

Just pick out the crankset you want most, buy the matching BB, and if you manage to wear it out, pat yourself on the back for all that enjoyable riding and treat the bike to a new BB.

My external bb's are failing now after 4 years. For me that is just not good enough. Looking online I've found that this is normal and many people get even less time out of their external BB. I have yet to find someone complaining that their square taper BB has failed after 4 years or less. I would convert my external to square taper if only I knew how.

Even cheap (Shimano UN-XX) bottom brackets usually last several years (IME), enough that the two I had replaced within 6 weeks on two different bikes were both frozen to the frame. It's a hassle to get them out, and if it takes a month of soaking (as the last one did) to remove it, you're without a commuting bike for that long. (Which is a great argument for N+1, but I digress.) After discussing with a few mechanics, I re-installed both new BBs with Teflon plumbers tape. You could also do annual maintenance on the BB, and grease them annually. (That's more hassle than I put up with.)

Or you could get one of the SKF bottom brackets. They're expensive, but sealed, and likely to last a very long time. I'd still install with Teflon tape.

Did you use grease at all? I like to smear a fresh coat onto both sets of threads whenever I install one.

SKF make excellent ST cartridge units cheaper than Phil Woods or ChrisKing.
I still trust Shimano UN52 to deliver years of service in all weathers with no maintenance.

I'd go with the cartridge. Ride it 'til it dies, then get another. I like to ride more than I like to work on 'em...

A great bang for the buck and perfect for a commuter.

Shimano UN55 Square Taper Bottom Bracket | Chain Reaction Cycles

Velo-Orange Grand Cru. Inexpensive, well-made, serviceable.
Bottom Brackets - Components

Shimano UN-55.