Square taper BB not lasting

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 The Potato 30 Nov 2022

My understanding was that the old type sealed internal BBs like the square taper would last for many years, so I fitted one to my converted SS commuting bike last year.

In that time I've been through 3, the first was a cheap £11 jobbie lasted 4m, so I though fair enough, I'll get a better one, so basic Shimano, lasted 3m, ok ill pay a bit more (£24) for a better Shimano one, 2 months!

Now I'm not heavy at 70kg, it's moderately hilly where I am, it's stored in a dry place, I don't know if it's because it's a singlespeed, but this just seems wrong.

Any thoughts?

 Jon Greengrass 30 Nov 2022
In reply to The Potato:

How did the BB fail?

How often do you clean the bike and how?

You say its a singlespeed, how is the chain tensioned, its too tight would be my guess.

OP The Potato 30 Nov 2022

Rarely needs cleaning, low pressure garden hose and a sponge.

Chain tension is by a spring loaded chain tensioner device, about the same or less than a derailleur

Failing as in a loud click that can eventually be felt through the cranks (defo not pedals etc).

Post edited at 17:07
 artif 30 Nov 2022
In reply to The Potato:

Personally I've done thousands of miles on Shimano ones without fault, even when abused on dh bikes, but that was a "few" years back. Broke a few crank arms, but never a BB.

These still seem happy with them

https://www.renehersecycles.com/why-square-taper-bottom-brackets/

 Jon Greengrass 30 Nov 2022
In reply to The Potato:

Sounds like you've done everything right. In my experience Shimano cartridge bottom brackets last for 1000s of miles. The only possible thing could be tightening the non-drive side cup too much but that would only be a problem for the style of BB that use actual cartridge bearing separated by a spacer rather than the classic Shimano cartridge style where both bearing are integrated into a complete assembly, which has the advantage of removing the possibility of the user altering the bearing pre-load.

Perhaps they've just learned the lesson from HT-II that there is a lot of money to be made in bad bottom bracket design, I noticed that the old design BB-UN55 and BB-UN72 are hard to get hold of and there is a new cheaper BB-UN300 design?

 nniff 30 Nov 2022
In reply to The Potato:

Are you sure it's the BB and not the square taper that's clicking?  If you take the chain off, hold the seat post and spin the crank, a failed BB will be detectable as a rumble though the seat post.  A click on the other hand rather suggests that the square taper is working loose, which is an old problem and why you don't see them much these days.

Changing the BB won't affect the likely culprit, which is most likely the square taper

 DaveHK 30 Nov 2022
In reply to The Potato:

> Failing as in a loud click that can eventually be felt through the cranks (defo not pedals etc).

You say defo not pedals etc but clicks can be notoriously difficult to diagnose, it could be pedal, pedal/crank thread, crank/BB interface, saddle, seatpost, frame,... Also, click does not necessarily mean replace the bb, it depends on how bad it is.

OP The Potato 30 Nov 2022
In reply to DaveHK:

I've got a cheap set of pedals used only for diagnosis of clicks

I always grease the spindle well before fitting the crank arms and I've checked they're still tight and the fitting is still square no rounding off.

Post edited at 17:59
 afx22 30 Nov 2022
In reply to The Potato:

> I've got a cheap set of pedals used only for diagnosis of clicks

> I always grease the spindle well before fitting the crank arms and I've checked they're still tight and the fitting is still square no rounding off.

That sounds like the problem then.  You’re not supposed to grease the interface between the square taper axle and the crank arms.  That allows them to go on too tight and typically deforms the square taper interface in the crank arm.  

I’ve seen this done wrongly many times (I used to run a bike shop).  The over tightening deforms the cranks, leading to more over tightening and so on.  First you get clicks and eventually the crank can fall off.

The correct thing used to be that the axle and crank should be cleaned, fitted, tightened to 45nm, ridden for 50 miles or so, then re-torqued.

Modern splined designs are way better.

 Dave B 30 Nov 2022
In reply to The Potato:

As afc says,  no grease. Or, I was once told, nose grease only... Anyone what told that? I don't grease. 

Yes, my old un72s from 2004 is still fine! 

 Wimlands 30 Nov 2022
In reply to DaveHK:

Agreed…I had to swap out the LH crank on my bike to stop the incessant creaking…

The creak followed the crank to the other bike I tested it on.

 artif 30 Nov 2022
In reply to afx22:

Might want to read the comments in the link I posted earlier. 

 elsewhere 30 Nov 2022
In reply to Wimlands:

> The creak followed the crank to the other bike I tested it on.

That's you knee clicking then

OP The Potato 01 Dec 2022
In reply to The Potato:

I'm still not convinced it's the axle/crankarm interface.

If it was 'too tight' and deformed the crank hole, why would the noise disappear with a new BB?

Reading what Artif linked to, they seem to agree about reforming the taper by tightening 

Post edited at 08:44
 Jon Greengrass 01 Dec 2022
In reply to The Potato:

If the BB is knackered you should still be able to feel the click and or roughness when you turn the axle by hand after its removed was this the case?

 Jon Greengrass 01 Dec 2022
In reply to Dave B:

no need to grease the interface with a steel crank, but with alloy cranks on steel axle I always use a little bit of copaslip, then I'm able to get it off again when the time comes, without resorting to scaffolding poles on the extractor tool.

 Prof. Outdoors 01 Dec 2022
In reply to Jon Greengrass:

Interesting point. In a reply to a public comment in the reneherse article linked above Rene suggests;

"Also lightly grease the tapers to get a good seat of the cranks and prevent galvanic corrosion between (aluminum) crank and (steel) spindle…"

To the OP - Does the click always happen at the same point in the revolution of the crank? Loose crank arms tend to click on the power stroke after coming over top dead centre. ie circa 1-3pm on a clockface. I find that a worn BB tends to rumble all the way round upon rotation.

If the click is heard at the same point each time on each failed BB I would definited be thinking of alternative sources. Rene Herse suggest checking chainring bolts as a potential source of the click. If all the teeth are not straight on the chainring it could be catching on the cage of the front derailleur.

 wbo2 01 Dec 2022
In reply to The Potato: I don't mind the bottom bracket that's linked to above but I'm roundly unconvinced by the merits of artisan Al crankarms - I'm still burnt by memories of Cooks Brothers and Middleburns offering.  Very pretty, very rubbish

 magma 01 Dec 2022
In reply to The Potato:

> I'm still not convinced it's the axle/crankarm interface.

> If it was 'too tight' and deformed the crank hole, why would the noise disappear with a new BB?

could be going loose over time which would also cause clicking/deform crank hole?... do you use a torque wrench?

Post edited at 14:19
OP The Potato 01 Dec 2022
In reply to The Potato:

Thanks all, ive checked all the things mentioned and am still at a loss.

Yes the click occurs in the same position (for now) which is as mentioned when the crank arm passes the 1 o clock position. From experience of the previous 2 BBs, this will deteriorate to a more sustained clicking / rumble.

Never mind, Ill go back to using HTII

 jkarran 01 Dec 2022
In reply to The Potato:

> I'm still not convinced it's the axle/crankarm interface. If it was 'too tight' and deformed the crank hole, why would the noise disappear with a new BB?

I'd guess with a repetitively loaded greased square taper you'll gradually work the thin film of grease which remained after you torqued it down out of the interface loosening the fit.

jk

 afx22 01 Dec 2022
In reply to The Potato:

> I'm still not convinced it's the axle/crankarm interface.

> If it was 'too tight' and deformed the crank hole, why would the noise disappear with a new BB?

if you were to fit the new BB, with grease, then that might quieten things for a few miles.  But the grease would move and the crank would start moving again (in relation the the axle) and your creaking would come back

btw, it was Madison UK (long time main importer of Shimano) who taught me not the grease the axle on square taper BBs.

You should clean and grade the threaded interface between the BB and the BB threads in the frame.  Water can get down the seat tube from above.  Regularly cleaning and regressing the seatpost and frame interface can help reduce water getting down to the BB shell.

 afx22 01 Dec 2022
In reply to Jon Greengrass:

> no need to grease the interface with a steel crank, but with alloy cranks on steel axle I always use a little bit of copaslip, then I'm able to get it off again when the time comes, without resorting to scaffolding poles on the extractor tool.

I used to find Copaslip was fine but just not necessary.  I can’t remember a crank extractor tool not doing the job.  Now getting a BB off a frame could be a challenge!

OP The Potato 01 Dec 2022
In reply to afx22:

> I used to find Copaslip was fine but just not necessary.  I can’t remember a crank extractor tool not doing the job.  

I can, and stripping the thread, and using a pipe and lump hammer...

 Jon Greengrass 01 Dec 2022
In reply to The Potato:

Did you use a torque wrench to install the cranks?

OP The Potato 02 Dec 2022
In reply to Jon Greengrass:

ive not used a torque wrench to fit any bike part, and ive built 11 in the last 20 years

2
 nniff 02 Dec 2022
In reply to The Potato:

> I'm still not convinced it's the axle/crankarm interface.

> If it was 'too tight' and deformed the crank hole, why would the noise disappear with a new BB?

>

Because you've taken the thing off and refitted it, and it will be seated well until it isn't and starts clicking again...

OP The Potato 02 Dec 2022
In reply to nniff:

That's plausible, so would need new crank arms then

 gravy 02 Dec 2022
In reply to The Potato:

In-board BB cartridges tend to be rubbish. 

If your bike will take outboard ones like Shimano Hollowtech II then consider changing your chainset and going for these instead. Most bikes that take a cartridge will take these.

I just went through cartridge after cartridge before moving to outboard bearings - they are much much better (for good reason). They are cheap, they last well, they ride well and they are cheap and easy to replace.

Cartridge bearings have to have the opposite bearings close together and in a small diameter race because everything is confined within the BB. Consequently the forces on them are high (because of the torque applied across the frame).  The outboard bearings are much wider apart and can run in larger diameter races and the stresses are much lower.  Coupled with that, the crank-shaft fixture is much better (making for a stiffer drive chain) and the whole lot weighs less.

Downside is the new crankset and a special spanner to fit them.  I reckoned this was cost neutral after two cartridges or about 6 months and a significant upgrade to boot.

Post edited at 18:44
2
OP The Potato 02 Dec 2022
In reply to gravy:

Aye thanks, I've got a ht2 crankset spare, i just thought square taper was meant to be longer lasting so tried that. 

Never mind.

 gethin_allen 02 Dec 2022
In reply to The Potato:

I've been told that one of the reasons why hollow tech BBs fail prematurely is because the BB shell faces aren't parallel and that getting the shell faced precisely will sort many issues. 

I can believe this in the case of carbon frames with press fit BB shells or threaded shells that are fitted independently but, in the case of metal frames and carbon frames with a full metal bb shell insert the faces should really be square and parallel.

 mattsccm 31 Jan 2023
In reply to gethin_allen:

Bear in mind that Gravy is very much going against conventional wisdom. Decent cartridge square tapers will last tens of thousands of miles. None of the newer Shimano Bbs can be classed as decent. 

Externals generally have exposed bearings, smaller balls and need the BB shell to be faced perfectly to allow perfect alinement. They tend to be more expensive if comparing like for like quality. Eg a basic SRAM GPX is somewhere qualitywise down there with a piece of Chinese junk that fetches maybe a third of its price. If you really want more info go and look at the CUK forum. 

 Hooo 31 Jan 2023
In reply to gravy:

I've never had a problem with square taper BBs. I think I've replaced one in my life. They just work. My current bike has Hollowtech II. The bearings have been fine, but yesterday the left crank fell off without warning. No obvious reason why. I've never heard of that happening with a square taper crank.

OP The Potato 01 Feb 2023
In reply to Hooo:

I have! Happened to me about 2003 on the path from greenfield to Manchester, didn't have the right size hex key on my multi tool but just managed to tighten it enough to get home

In reply to The Potato:

As Gethin mentioned, if it *is* the bearings going and not the crank arm / interface *and* you've had issues in the past with HTII going quicker than expected, have you had the bottom bracket shell on your frame accurately faced? Less common that this causes issues on square taper, but it's still possible.

You could always get one of those expensive ones of that annoying guy on youtube - Search for Hambini.

I wrecked 10s of square taper cranks as a kid on various bikes, but it was always the crank interface and for years I had no idea you weren't meant to grease them. The only BBs I've had the bearing actually fail in are HTII...  (oh, no, maybe I wore out the one on my city bike which gets zero maintenance and has been hammered for 17 years.)

I think I replaced it more than 10 years ago square taper, alu cranks. Regularly bunny hop up and down kerbs, winter, summer etc.


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