Bottom Bracket Shells

Notice that the title of this section is not “bottom brackets”. Right now, bottom brackets (and the cranks they are compatible with) come in two dominate styles: Square Taper and External. There a bunch of variations and that kind of annoys me, sure. But the industry as a whole seems to keep coming back to square taper bottom brackets with 3 piece cranks (which I love) and 2 piece “hollow-tech” cranks with external bottom brackets (which I don’t love but I also don’t outright hate).

2 piece cranks were invented to modernize a couple of things about crank systems, but to understand what that means, we are gonna need a short history lesson. (WHEN WERE ONE PIECE CRANKS IN ALL OF THIS??) A long time ago, all bike cranks were “cotter and pin” style. These are held on by a little pin that is hammered into place. (ADD SOME MORE HISTORY/CONTEXT AND MAYBE A DIAGRAM) When I first learned how they worked, I was shocked they were even able to stay on the bike. After that, square taper bottom brackets became the standard. (HOW DID THEY LAND ON A SQUARE TAPER FOR THESE??) These are more secure, and are much easier to remove. They did introduce a new standard for bottom brackets and require special tools to remove (bad), but they became so widely adopted that I don’t really care.

The reason I am ok with this particular example of competing standards is because they are only kind of competing. They are both compatible with the same bottom bracket shell. If you really care about rigidity and weight, you can swap out a three piece crank for a two piece crank and you can keep literally everything else on the bike identical, including the chainrings and the pedals. Sure, you have to know what you are doing to make sure everything lines up, but it is technically possible. This is what I would call “non-invasive” innovation. It is innovation that focuses on improving as much as possible within the bounds of the current standards, introducing minimal compatibility issues to future users. 1 inch threadless headsets are another example of this (even though they are basically dead at this point for reasons I cant find a good answer to).

I do prefer square taper. Some two piece cranks can be taken off with just a allen key, which should entice me, but aftermarket self extracting crank caps can be added to any square taper crank set since like the 70s and boom now you just need an allen key for square taper as well. Plus the tools for removing square taper bottom brackets are much more standardized and easy to find in your local co-op.

No, what I mainly take issue with is bottom bracket shells. 68 BSA is great. I am not convinced 73 BSA was really needed but it has plenty of support so fine. 100 BSA makes sense for fatbikes, sure (still not entirely clear what the purpose of those are but whatever). Everything else is insane to me. I had a guy come into the bike shack looking for a tune up on his road bike and asking if we had the tools to remove his press in bottom bracket. I said no, I have never worked on a bike with a press fit bottom bracket before and he should go to licensed mechanic for that kind of work, and he responded, I shit you not, “Oh, so you guys dont work on bikes made in the last 20 years or so then, huh? Only old stuff?”

Now, he wasn’t mad at us, just kind of disappointed. And after some convincing he decided to go to gregs. In case you don’t know, what is crazy about this is that press in bottom brackets were only a thing for like 5 years in the late 2010s and early 2020s. And they were only available on high end carbon racing bikes. That’s it. As far as I’m aware, you cannot buy frames with press fit bottom brackets anymore, largely because people hated them.

Why were they invented? To save a unbelievable small amount of weight. I’m talking grams here. They also provided a wider diameter bottom bracket, which allowed for larger bearings and a stiffer frame. Two things that I’m sure made the bike a whopping 0.5% more efficient. What did they do for the average cyclist? Well it took the money from their wallet and turned that into a bike that was completely obsolete and unsupported in 3 years. Have fun finding 3rd party replacement parts and tools for your now niche retro racing bike.

What did bike companies do after press fit? A few moved back to 68 BSA (so based holy shit), but some moved onto the new big thing: T47. The innovation? It is the exact same dimensions as the press fit bottom bracket but (drum roll please) it is threaded. One of the reasons people hated the press fit standard was because press fit bottom brackets would come loose really easily and start creaking really loudly under load. Adding threads fixed the problem, sure, but left us with YET ANOTHER bottom bracket shell standard. T47 bottom brakets require a whole new frame, with a whole new bottom bracket and all new tooling to service. Great. Thanks guys. It is maddening to me to read articles about this invention citing the downsides of this new shell standard as “50-100 extra grams” rather than making other standards obsolete for absolutely no reason. Well, trying to make other standards obsolete. I’m convinced that 68 BSA will live on till the end of civilization at this point.

E-Bikes and Gearbox bikes take this problem and multiply it 10 fold. Most higher end e-bikes these days use mid-drive motors, which (trust me) feel great. However, EVERY SINGLE ONE comes with its own new bottom bracket standard. Fuck RIGHT off please. Oh Bosch decided to make a new standard for its mid drive motors? Guess your bike is just trash now the moment the motor fails. Have fun!

Weirdly enough, the most recommended after market mid drive motors are actually 68 BSA specific. So the new standards being made by the big players are clearly not-necessary. I’m sure it’s 3% more efficient or whatever, but its not worth boxing my $5000 purchase into a standard that can just go away one day. Stop letting companies get away with this shit.

And on that topic, Pinion gearboxes. The touring crowd loves these things, and I love the touring crowd, so what gives? Well, same problem as the mid-drive motor: new bottom bracket standards. Pinion goes out of business and now your frame is obsolete. Pinion is probably doing fine right now but that’s not the point. Pinion bikes are extremely expensive for what they are and, again, I’m not spending that kind of money on something that depends on 1 company to keep working. Especially when I can get essentially the same benefits from a Rohloff hub that is less expensive and goes out of it’s way to be as compatible with as many existing bike frames as possible. What a concept!

Anyway, please keep buying 68 BSA bike frames. Remember: incompatibility =/= innovation.