Lowering stem, carbon steerer, bung length.

imposter2.0

masjer said:

I'll try and explain in a way you'll understand. The bung is fitted with about 8nm. This imparts a considerable outward force on the internal walls of the tube. The stem uses pinch bolts, causing an inward force on the tube walls. Both inward and outward pressures cancel each other making for a stronger tube. Simple.
An analagy- think of an unopened coke can. You can't crush it because the walls are being pushed outward. Open can, pressure is released, you'll probably be able to crush the can.
In terms of weight saving a bung is very heavy since people spend vast sums to save just a few grams.Simple.
Anyway think of Gorilla Greipel sprinting, he'll be wanting a strong stem/steerer combo ie with a bung in it.

I see you've reach the 'patronising' stage...

I've never seen a steerer bung with a recommended torque setting, so I'm guessing you made that up. The required torque is only that which is needed to stop the bung from pulling up as you tighten the headset - nothing more. Why do you think the outside of the sleeve is knurled? What other reason would there be for the sleeve to be ale to 'grip' the inside of the steerer. If the purpose is to provide an opposing outward force, then no knurling would be required.

Your Greipel analogy is a poor attempt at confirmation bias and completely misunderstands the forces that are applied during that kind of effort - and none of them relate to the risk of the steerer not being resistant to a crushing force.

MattFalle

why oh why oh why oh why would someone pulling on a set of handlebars affect compression on a disconnected tube?

what is he on abaht?

masjer

You have a constant patronising tone, probably why many have left the forum.
Now you're bringing knurling to the table. Of course the knurling is there to provide grip. It goes without saying.
About the recommended torque- have you seen how many people's (on here) bungs pull up because they are inadequately torqued.
The analogy makes perfect sense, if you've weakened the steerer by not using a bung, the ENORMOUS forces from sprinting (on the steerer) might end in a face plant.
If it wasn't for your ego we could move on.
Why did you describe your initial statement as "controversial" if it's common knowledge that bungs (according to you) don't impart strength? Still zero evidence from you.

lesfirth

pblakeney said:

lesfirth said:

Ben6899 said:

And there’s a reason that underground tunnels are tubular in section…

The reason is that it is the easiest shape to make them.

Only it isn't.
On either front.

Ok ,if you say so, but I do not remember seeing any tunnel boring machines that made anything other than round holes. Maybe you have.

masjer

"I've never seen a steerer bung with a recommended torque setting, so I'm guessing you made that up. The required torque is only that which is needed to stop the bung from pulling up as you tighten the headset - nothing more. Why do you think the outside of the sleeve is knurled? What other reason would there be for the sleeve to be ale to 'grip' the inside of the steerer. If the purpose is to provide an opposing outward force, then no knurling would be required.

Your Greipel analogy is a poor attempt at confirmation bias and completely misunderstands the forces that are applied during that kind of effort - and none of them relate to the risk of the steerer not being resistant to a crushing force. "

Bung with 8NM printed on it. You haven't seen enough bungs

imposter2.0

masjer said:

You have a constant patronising tone, probably why many have left the forum.
Now you're bringing knurling to the table. Of course the knurling is there to provide grip. It goes without saying.
About the recommended torque- have you seen how many people's (on here) bungs pull up because they are inadequately torqued.
The analogy makes perfect sense, if you've weakened the steerer by not using a bung, the ENORMOUS forces from sprinting (on the steerer) might end in a face plant.
If it wasn't for your ego we could move on.
Why did you describe your initial statement as "controversial" if it's common knowledge that bungs (according to you) don't impart strength? Still zero evidence from you.

Patronising, and now an ad hominem

I hardly post on here anymore (today is an exception thanks to you ), so if people are leaving the forum, I'm guessing it's more to do with the complete absence of any effective forum management and the associated terrible functionality.

If you think your analogy makes perfect sense, then there's not much else to discuss, unfortunately.

My initial post was controversial (as I have already told you) - because there are still people like you out there that think the bung provides some kind of structural assistance to the steerer. And here you are - rocking up to basically prove my point, with your logical fallacies and cr@p analogies.

As for evidence - what do you need? All that should be necessary is to look at a bung, look at how it is made and how it expands. Only a complete dunce would fail to see that something like that cannot provide adequate structural assistance. And yet, here you are.

Here's a test for you. If steerer bungs are so critical to the structural integrity of carbon steerers - why is it that no aftermarket carbon fork comes with its own proprietary steerer bung? Finally, presumably you also have some kind of reinforcing bung inside your carbon seatpost and also inside your carbon handlebars (if you have them) as clearly they clamp in the same/similar way. Looking forward to your answers...

orraloon

If anyone wants to give me a bung, bring it on. Cash of course.

MidlandsGrimpeur2

@johngti

Like others on the thread, I think the question of whether the longer bung aids structural strength is open to debate.

What I would say is check the frame warranty. I had a cracked fork steerer last year. Similar to your setup, the bung did not reach far enough down the steerer tube to exceed the lower stem clamp bolt. As a result, the warranty claim was denied as it was argued the fork and bung had been incorrectly fitted against manufactuers instructions. Regardless of whether the longer bung does make a structural difference it may still be worth it should any future warranty issue occur.

masjer

Yet again you are being condescending.
You're so blatantly ignorant, every time you ask me to explain something i do. You make the initial statement, then come up with zero.
Again because seatposts are engineered to do their job they are made strong enough to do their job, unsurprisingly.
Both seaposts and handlebars are clamped more centrally, totally different.
Ever seen a seatpost installed at the end (fully extended) it would break when someone sat on the saddle. Stems/bungs are installed at the end of a tube NOT in the middle. Wake up dunce!!
You said bungs don't have a torque figure (and I made it up) , the first one I look has it clearly stamped on it -photo above. Blind as well as dense.

Ben6899

lesfirth said:

pblakeney said:

lesfirth said:

Ben6899 said:

And there’s a reason that underground tunnels are tubular in section…

The reason is that it is the easiest shape to make them.

Only it isn't.
On either front.

Ok ,if you say so, but I do not remember seeing any tunnel boring machines that made anything other than round holes. Maybe you have.

It’s a happy coincidence that TBMs work best at forming circular portals, to be fair.

TBMs weren’t always used and yet - for example - the old, cast-iron tunnels on the London Underground network are tubular. Possibly easier to construct/install, but the *roughly* even earth pressures around the tube help to maintain its integrity.

Like a stem on a steerer tube - make the steerer tube oval and it’s another story.

imposter2.0

masjer said:

Bung with 8NM printed on it. You haven't seen enough bungs

I've seen plenty. But I still haven't seen one with a recommended torque setting. The setting given there is a maximum. It's a small but significant difference. And it's the reason why you're still not getting it.

imposter2.0

masjer said:

Yet again you are being condescending.
You're so blatantly ignorant, every time you ask me to explain something i do. You make the initial statement, then come up with zero.
Again because seatposts are engineered to do their job they are made strong enough to do their job, unsurprisingly.
Both seaposts and handlebars are clamped more centrally, totally different.
Ever seen a seatpost installed at the end (fully extended) it would break when someone sat on the saddle. Stems/bungs are installed at the end of a tube NOT in the middle. Wake up dunce!!
You said bungs don't have a torque figure (and I made it up) , the first one I look has it clearly stamped on it -photo above. Blind as well as dense.

Mate, you've lost it. The irony here is overwhelming.

Your inference is that carbon steerers are deliberately not made strong enough, so need to be supported by some aftermarket device, over which the fork manufacturer has no control. And you call me dense...

Also, you need to learn the difference between maximum and recommended torque. I can't be bothered to explain it.

masjer

imposter2.0 said:

masjer said:

Bung with 8NM printed on it. You haven't seen enough bungs

I've seen plenty. But I still haven't seen one with a recommended torque setting. The setting given there is a maximum. It's a small but significant difference. And it's the reason why you're still not getting it.

Contradicting again! Clutching at straws now.
Most torque figures printed on components are a max figure, but it sure gives you a clue on how tight it should be.
Nothing to say about MidlandsGrimpeur's warranty claim? Seems like manufacturer was stating the bung was there to provide support against crushing force under the lower stem bolt. Who would believe it.

imposter2.0

masjer said:

imposter2.0 said:

masjer said:

Bung with 8NM printed on it. You haven't seen enough bungs

I've seen plenty. But I still haven't seen one with a recommended torque setting. The setting given there is a maximum. It's a small but significant difference. And it's the reason why you're still not getting it.

Contradicting again! Clutching at straws now.
Most torque figures printed on components are a max figure, but it sure gives you a clue on how tight it should be.
Nothing to say about MidlandsGrimpeur's warranty claim? Seems like manufacturer was stating the bung was there to provide support against crushing force under the lower stem bolt. Who would believe it.

What contradiction? A recommended number is not the same as a maximum number - or do you disagree?

The only clue it gives is not to exceed the maximum figure. As for the warranty claim thing - 'manufacturer avoids warranty claim by relying on cod science'. Who would believe it?

masjer

Contradiction-"I've never seen a steerer bung with a recommended torque setting, so I'm guessing you made that up"
Now-" I've seen plenty with Max torque"
Talk about splitting hairs! I understand very clearly the difference between recommended and max as it's the most simple concept to grasp.
Warranty claim- From a fork manufacturer -Even a too short bung affects the structural integrity, let alone no bung!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Nighty Night.

orraloon

Guys. Just. Gimme. Da. Bung.

N0bodyOfTheGoat

I am Bungholio!

paulbnix

All the bungs I have are constructed with a solid piece at the top which is the same diameter as the steerer.
This is normally positioned just below the top of the stem clamp and should resist compression.

imposter2.0

masjer said:

Contradiction-"I've never seen a steerer bung with a recommended torque setting, so I'm guessing you made that up"
Now-" I've seen plenty with Max torque"
Talk about splitting hairs! I understand very clearly the difference between recommended and max as it's the most simple concept to grasp.

Well, clearly you are not grasping it - or else you wouldn't see it as a contradiction, or as 'splitting hairs'. You're confusing yourself now.

masjer said:

Warranty claim- From a fork manufacturer -Even a too short bung affects the structural integrity, let alone no bung!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Nighty Night.

Cognitive dissonance can be difficult to overcome...

pblakeney

I think some people need to get a room together.
Don't care if it's a fight or a fuck but get over it.

imposter2.0

pblakeney said:

I think some people need to get a room together.
Don't care if it's a fight or a censored but get over it.

You think Masjer and I should 'get a room together' - in order to spend the night? Is that what you're saying? Or are you just trotting out a tired old internet trope?

johngti

Blimey, I thought it was a simple question.

MattFalle

johngti said:

Blimey, I thought it was a simple question.

it is depending on whether you know what you're talking about or not so much if you are Masjer.

johngti

MattFalle said:

johngti said:

Blimey, I thought it was a simple question.

it is depending on whether you know what you're talking about or not so much if you are Masjer.

Honestly? It’d be nice if people could get that passionate about stuff that actually matters. This was a thread about carbon steerer bungs.

Masjer has massively overstated it though. The strength in a cylinder comes via forces applied from outside in. Apply pressure from the inside and it’s more likely to crack, surely? The coke can analogy isn’t the same because they’re sealed containers. Different forces innit.

Anyway, don’t think I’ll bother too much.

MattFalle

Well, tbf, he was wrong about everything, so don't just pick on him for that. that would just be unfair.

i particularly like his description of fact describing how a cycling man would generate enough torsional power to rip a carbon fibre tube apart whilst cycling and how a 2 inch hollow aluminium tube would stop this.

pblakeney

lesfirth said:

pblakeney said:

lesfirth said:

Ben6899 said:

And there’s a reason that underground tunnels are tubular in section…

The reason is that it is the easiest shape to make them.

Only it isn't.
On either front.

Ok ,if you say so, but I do not remember seeing any tunnel boring machines that made anything other than round holes. Maybe you have.

Missed that. - That's the hole, not the casing.
Too late, off topic and lost interest.

masjer

On a final note, yet more evidence:

Taken from the Columbus fork installation manual:

"CAUTION
In the case of carbon forks, ensure that the contact area between the
internal walls of the steerer tube and the expander matches with the
area where the stem applies pressure to the steerer tube.
The integrity of the steerer tube material cannot be guaranteed if an
incorrect combination of components is used and may result in
breakage.
If the overall height of the lower spacers used decreases, it is necessary
to reduce the height of the steerer tube by cutting it further, as
indicated in (1)."

MattFalle

shame no one told Cannondale or Canyon.

perhaps you should drop them a line.

masjer

Hey, MattFalle I see you're enrolling on a bicycle mechanics course. I think it's a good idea for you. You might actually gain some basic mechanical know-how -as long as you listen.

whyamihere

Not going to get into the debate about whether the bung is structural, there are some manufacturers who say they are and some who don't, if you have a bike where the manufacturer states you need to use a specific bung then do it, for warranty reasons if nothing else. However, the advice that was given as being generic about installing a star nut into a carbon steerer is stupid and dangerous. There may have been a couple of forks which were been designed to take them, but that's not a universal thing. If it was, fork and bike makers wouldn't supply their forks with bungs.