Going from a triple to a double – what don’t I know?

[Steve O]

@hozn 158946 wrote:

I have found rather little correlation between PRs and equipment.

Au contraire. I have never set a PR on my unicycle.
[emoji6]

[vvill]

After switching one of my bikes from square taper to external BB I ended up switching all of them (even the beater bikes). I much prefer them!

[hozn]

@EasyRider 158969 wrote:

Yeah, I get the compatibility with modern parts, and figured with larger bearings, durability should be better. But in practice, doesn’t having the bearings outside the frame expose them to grit and grime, especially off-pavement, and make them go kaput sooner? Kaput meaning rough and unpleasant feeling, not necessarily failure like the above picture?

Yeah, I generally replace external BB bearings around 6k miles, but that is because they start making noise. I’ve never had one fail catastrophically. The worst experience I had was a Chris King BB where it had sufficiently seized in the frame to destroy the threads when removing it. That was because it was in for a year thanks to using the grease injector gun. That was a waste of money, though, since it only lasted 1.5x as long as a $20 GXP BB, required frequent service, and cost 7x as much.

[EasyRider]

@vvill 158974 wrote:

After switching one of my bikes from square taper to external BB I ended up switching all of them (even the beater bikes). I much prefer them!

What is it that you prefer about them? I am curious about going external BB for an upcoming build but don’t yet have a rationale, except that despite having the tools and experience to install and remove square taper cranks, doing it still makes me a bit apprehensive.

[hozn]

@EasyRider 158977 wrote:

What is it that you prefer about them? I am curious about going external BB for an upcoming build but don’t yet have a rationale, except that despite having the tools and experience to install and remove square taper cranks, doing it still makes me a bit apprehensive.

I also prefer them even if the longevity may less clear-cut.

They are easier to install/remove IMO. And you can replace the cartridge bearings (with some equipment) making them cheaper. And they are lighter, generally. But mostly they are the standard for standard threaded BB shells now and any nicer modern crankset I can think of will use some form of external BB for threaded shell.

Aesthetically I also like the closer fit / tighter spacing of crankarms against frame when using external cups, but that isn’t a major consideration for me when it comes to the BB. I want one that is quiet for as long as possible and then is inexpensive and easy to replace when that is no longer true.

[Harry Meatmotor]

I don’t see why one would choose to run a square-taper BB when a stronger, cheaper, lighter alternative exists and is now commonplace in the industry.

[dkel]

@Harry Meatmotor 158991 wrote:

I don’t see why one would choose to run a square-taper BB when a stronger, cheaper, lighter alternative exists and is now commonplace in the industry.

Because not all cranksets are compatible with external BBs.

[vvill]

What hozn + HarryMm said. Additionally, in my experience external BBs also eliminate the futzing around with square taper BB spindle measurements (just look at this https://www.sheldonbrown.com/bbsize.html ) and also issues with having to tighten the cranks enough to stay on the square tapered part of the BB, whilst not having them too tight. Hollowtech II / GXP are just sooo much easier to deal with (and other systems too I assume – my bikes are all one of those two).

There might be a special crankset like a Rene Herse where you could justify a square taper but then I’d also want a quill stem and downtube shifters, I guess. And all brake cables protruding up and out of the hoods. And there’d better be some mighty fine lug work on the frame.

[dkel]

Dismal! Where are you when we need you?!?

[mstone]

@Harry Meatmotor 158991 wrote:

I don’t see why one would choose to run a square-taper BB when a stronger, cheaper, lighter alternative exists and is now commonplace in the industry.

And with so many standards to choose from!

[huskerdont]

I appreciate this discussion because I find the different standards/sizes really confusing and I always have trouble remembering which tool is needed or if I have the right tool. I think I’ve just about navigated them all successfully, although I did crimp a shell once by not including the needed spacer.

Tangential/OT question: is it abnormal for a BB30 on a new bike (260 miles) to be pushing out (clean) grease? I have never noticed this before on any other bike, but cleaning the rain gunk off last night, I noted a line of grease, with an occasional larger blob of it. I can remove the crank this weekend and take a look, but it’s a new bike so I could also take it back to the shop since it seems to me that the grease should remain inside the BB.

[drevil]

@Harry Meatmotor 158991 wrote:

I don’t see why one would choose to run a square-taper BB when a stronger, cheaper, lighter alternative exists and is now commonplace in the industry.

The reasons I can think of:

1. Cost – have a cheap bike, townie or fixie you don’t want to spend a lot of money on? You can get set up with a square taper crank and BB for <$60 with a square taper setup.
2. Custom(ization) – Six years ago, I had my custom fat bike designed to have the shortest chainstays up until then (415mm, but be able to clear a 4″ tire). This required a custom BB (it was the widest Phil Wood made ). ShRAManoFace* had no 2-piece cranks that would even be close to fitting at the time, and they still don’t AFAIK.
3. Need a crankarm length that isn’t 170mm-180mm – I use 165mm crankarms on most of my good bikes. I have never seen that length from ShRAMano in a configuration I wanted (I usually put on bash guards, which needs to be able to be mounted in the outer position).

All that said, if I ever have a custom bike made again, it will use a 2-piece crank and be off the shelf. For reasons already mentioned (bigger bearings, more durability, easier installation and removal), I will always choose 2-piece cranks.

*- Shimano, SRAM, RaceFace

[TwoWheelsDC]

@huskerdont 159002 wrote:

I appreciate this discussion because I find the different standards/sizes really confusing and I always have trouble remembering which tool is needed or if I have the right tool. I think I’ve just about navigated them all successfully, although I did crimp a shell once by not including the needed spacer.

Tangential/OT question: is it abnormal for a BB30 on a new bike (260 miles) to be pushing out (clean) grease? I have never noticed this before on any other bike, but cleaning the rain gunk off last night, I noted a line of grease, with an occasional larger blob of it. I can remove the crank this weekend and take a look, but it’s a new bike so I could also take it back to the shop since it seems to me that the grease should remain inside the BB.

Did a shop put it together? Maybe they just used a ton of grease to lube the shell and some has come out with pedaling pressure? I guess if it’s coming out of the bearing itself, that wouldn’t be a great sign…

[EasyRider]

@drevil 159005 wrote:

The reasons I can think of:

1. Cost – have a cheap bike, townie or fixie you don’t want to spend a lot of money on? You can get set up with a square taper crank and BB for <$60 with a square taper setup.
2. Custom(ization) – Six years ago, I had my custom fat bike designed to have the shortest chainstays up until then (415mm, but be able to clear a 4″ tire). This required a custom BB (it was the widest Phil Wood made ). ShRAManoFace* had no 2-piece cranks that would even be close to fitting at the time, and they still don’t AFAIK.
3. Need a crankarm length that isn’t 170mm-180mm – I use 165mm crankarms on most of my good bikes. I have never seen that length from ShRAMano in a configuration I wanted (I usually put on bash guards, which needs to be able to be mounted in the outer position).

All that said, if I ever have a custom bike made again, it will use a 2-piece crank and be off the shelf. For reasons already mentioned (bigger bearings, more durability, easier installation and removal), I will always choose 2-piece cranks.

*- Shimano, SRAM, RaceFace

Since drevil is my ask-questions-guy, does that mean that chainline on two-piece cranks/external BB is not at all adjustable? I do like that about square taper cartridge spindles … you can use them on all sorts of bikes. If the chainstays are wide or narrow, you just get a wide or narrow cartridge so they don’t hit the chainstay. Varying spindle length is also useful for fixed gear conversions.

[Harry Meatmotor]

@dkel 158993 wrote:

Because all modern cranksets are compatible with external BBs.

FTFY.

Aside from running track cranks (144BCD), or old school shiny stuff, or bargain-basement bikes, there really isn’t a good non-retro-grouchy reason.

And when you get down to brass tacks, there’s really only 3 major (and one minor) BB spindle standards nowadays: Shimano Hollowtech II (24mm), SRAM GXP (24/22mm), Cannondale BB/PF30 and derivatives (30mm), Campagnolo UltraTorque (25mm).

So, by running outboard bearings you can run just about any of the modern spindle sizes with only 3 different bottom bracket cup sets. I’d take that over futzing around with 107mm, 110mm, 113mm, 115mm, 118mm, 122.5mm, and 127mm spindle lengths in both 68mm and 73mm shell width (14+ choices, total), while using 1mm shell spacers in some cases to get specific crank/fder/frame spacing and chainline issues accommodated, just so I can keep a square taper JIS standard.

[Author]

Posts