Snapped spindle

[wafter]

Are Hollowtech cranksets more or less likely to fail than square taper?

I've had one of each now in my personal experience.

Maybe Hollowtech are *less* prone to sudden failure?

That's an interesting question.

How did your ST crankset fail - I assume it was the arm failing at the interface with the spindle rather than the spindle itself...?

From this perspective I'd expect the hollowtech less likely to fail since the steel axle is a more fatigue-resistant material than the ally of a typical arm and doesn't have any obvious stress raisers like the corners of the axle holes on the ST crankset.

Again I'd expect the HT axle to be designed to last indefinitely, damage notwithstanding.

 

[roubaixtuesday]

How did your ST crankset fail

The crank itself snapped in half, presumably from a flaw in the casting.

But a more interesting question is what's the rate of failure for each system, not one person's individual experience.

 

[roubaixtuesday]

Once again, a lovely photo that perfectly illustrates the spiral failure of a torque tube. And to think, all that just from left leg power. A failure of true beauty. Engineer's porn.

Yes indeed. Reminded me of undergrad engineering test pieces.

 

[chriswoody]

What intrigues me is the fact that the two failures documented on this forum have been Shimano cranks, yet whilst they devised this standard, they aren't the only ones using it.

For example I have a Race Face Aeffect crankset on my Gravel Bike that also has a 24mm spindle running through standard outboard bearings and I know there are various others out there as well. SRAM decided to go their own way and whilst their system looks similar they run a 27mm Spindle for increased rigidity.

Now Shimano have undoubtedly sold many more of this style of cranks than anyone else, so statistically they undoubtedly will have more failures, but it does intrigue me whether this is a failure of the design or a Shimano specific failure. Though with such a small sample size, it may well just be one of those things, failures are bound to happen?

 

[Yellow Saddle]

What intrigues me is the fact that the two failures documented on this forum have been Shimano cranks, yet whilst they devised this standard, they aren't the only ones using it.

For example I have a Race Face Aeffect crankset on my Gravel Bike that also has a 24mm spindle running through standard outboard bearings and I know there are various others out there as well. SRAM decided to go their own way and whilst their system looks similar they run a 27mm Spindle for increased rigidity.

Now Shimano have undoubtedly sold many more of this style of cranks than anyone else, so statistically they undoubtedly will have more failures, but it does intrigue me whether this is a failure of the design or a Shimano specific failure. Though with such a small sample size, it may well just be one of those things, failures are bound to happen?

Stop buying lightweight components and buying by the gram and the problem will go away.

 

[chriswoody]

Stop buying lightweight components and buying by the gram and the problem will go away.

How on earth is this a reply to what I posted? The original post showed a Shimano crank set that had failed.

There are three possibilities here, it's a problem of design, i.e, a thin walled spindle. A Shimano manufacturing fault or just a statistically likely failure given how few faults are documented and how many there are.

You had already said you believed it was statistical failure and there was nothing to see here. I happened to concur.

My post was more a rhetorical question about the fact that the design itself is used by many different manufacturers, not just Shimano, so if it was a problem of poor design then surely we'd be seeing failures from them as well.

As for my cranks, they we're on the bike from the factory because they are a much better design than the equivalent SRAM cranks and after 20 odd thousand kilometres they are still going strong. I have no concerns or worries about them and would happily recommend Race Face cranks to anyone.

 

[Jameshow]

Once again, a lovely photo that perfectly illustrates the spiral failure of a torque tube. And to think, all that just from left leg power. A failure of true beauty. Engineer's porn.

Stop feeding the engineers......keep them back in the basement below the IT crew!!

They know exactly who to blame - the accountants!!

 

[Drago]

Stop buying lightweight components and buying by the gram and the problem will go away.

Indeed. I regularly chortle to myself when someone obsesses about grams off their bike while completely ignoring the kilograms on their waistline.

 

[Yellow Saddle]

How on earth is this a reply to what I posted? The original post showed a Shimano crank set that had failed.

There are three possibilities here, it's a problem of design, i.e, a thin walled spindle. A Shimano manufacturing fault or just a statistically likely failure given how few faults are documented and how many there are.

You had already said you believed it was statistical failure and there was nothing to see here. I happened to concur.

My post was more a rhetorical question about the fact that the design itself is used by many different manufacturers, not just Shimano, so if it was a problem of poor design then surely we'd be seeing failures from them as well.

As for my cranks, they we're on the bike from the factory because they are a much better design than the equivalent SRAM cranks and after 20 odd thousand kilometres they are still going strong. I have no concerns or worries about them and would happily recommend Race Face cranks to anyone.

Relax Max. I have no idea what you buy or don't buy. If your Race Face crank uses the 24mm design but with a thicker tube (I.e. wieghs more), then you did it for the right reason. My point is that the market wan't lighter components but simultaneously expect durability. As Keith Bontrager said, " light, cheap strong, choose two".

 

[wafter]

The crank itself snapped in half, presumably from a flaw in the casting.

But a more interesting question is what's the rate of failure for each system, not one person's individual experience.

That's interesting - did it actually fail in the middle of the arm or at the interface with the BB spindle?

Assuming it's made of ally then failure will be a case of "when" not "if" since the material has no lower fatigue limit so subject to enough cycles it will fail.

It would certainly be interesting to see failure figures for both types of system; unfortunately I don't know of any reliable way of getting such numbers.

Probably worth interrogating an old bike mechanic / shop owner if you know any!

 

[roubaixtuesday]

That's interesting - did it actually fail in the middle of the arm or at the interface with the BB spindle?

In the middle of the arm. It's a long time ago, but as I recall it was a classic fatigue failure; you could see the original flaw and then the crack having slowly propagated from it.

Google tells me that failures of either arm or spindle at the interface are a thing.

Happened literally right in front of a bike shop who I still suspect of having a crank death ray destroyer gun to boost business, taking aim at unsuspecting passing students.

 

[silva]

He would have been replying to your unedited post, you realise that?

He quoted this:

Hollowtech 2 has its bearings external - left and right OUTside the bottom bracket, so not protected by it, more exposed to dirt and water, whereas in the simple and durable square taper case, they sit INside. I'm sure you know so why ask?
This is even regardless seals. The bearings have additional protection.

... which wasn't edited:

Hollowtech 2 has its bearings external - left and right OUTside the bottom bracket, so not protected by it, more exposed to dirt and water, whereas in the simple and durable square taper case, they sit INside. I'm sure you know so why ask?
This is even regardless seals. The bearings have additional protection.

You claim here "outboard" as less in the way of front wheel spray, but that's even when riding straight a cone that is wide enough to reach the chain, again further than the external bearings.
Also, rain dripping from the riders coat drips on the bottom bracket location, in case external bearings outside the enclosure.

... I added a second remark, pointing out that bringing bearings "outboard" doesn't place them more away from rain/dirt, rather the contrary.

There is a difference between editing a post and editing what was already in the post, you realize?
The square taper design is a compact assembly with bearings/sealings/whatever fitting entirely within the frame shell, while the hollowtech 2 design brings it all outside it, more exposed to rain / dirt.

 

[silva]

Indeed.. the only factor governing the ID appears to be how thin Shimano think they can go on the wall thickness to save mass; which of course is a large selling point of the design.

Safety critical parts like this shouldn't "just fail" in normal use without some exacerbating factor like mechanical damage or corrosion.

Personally I'd take the penelty of a few extra grams for a thicker wall if it removed the possibility of breakages like this.

That's why I stated that the hollow technology is a leap forward for the racing part of mankind (until every1 is on hollow) that want to spend 2-3 times bucks, but a step backward for the rest of mankind that don't want to spend 2-3 times bucks with not any benefit from it.
Buy a default 2 kg bag apples in supermarket, put it in your panniers, the 130 grammes hollow benefit is less than the smallest official caliber (150 gram) apple.
The benefit of hollow technology is also achieved by filling your liter bidon 87% full. Or, a pee along the road. Or, nothing in the pocket(s) of your shirt, or wearing no shirt.
For all but the racing 1 sec on 1 km matters club, hollow technology is a lump sum bucks less on the short and the long term. Of course, if you say I wanna help bike industry to survive then it's charity, nothing wrong with that. A good nice chat with a salesman is also worth bucks. See you next time Fred!

 

[silva]

That's interesting - did it actually fail in the middle of the arm or at the interface with the BB spindle?

Assuming it's made of ally then failure will be a case of "when" not "if" since the material has no lower fatigue limit so subject to enough cycles it will fail.

It would certainly be interesting to see failure figures for both types of system; unfortunately I don't know of any reliable way of getting such numbers.

Probably worth interrogating an old bike mechanic / shop owner if you know any!

https://en.wikipedia.org/wiki/Torsion_(mechanics)

 

[Ming the Merciless]

that want to spend 2-3 times bucks

Replacement HT2 bottom brackets are typically £15. The OPs crankset has cost them approx 0.3p per mile. It is hardly mega bucks.