[slcpunk21]

I'm confused on this whole theory. I have searched and can't find anything that answers my question exactly. So here we go

Ok in my head this is what I think. A smaller diameter tube is a more compact sound structure. If you have a larger tube you have more surface area and thus allows the walls of the larger headtube to be ovalized/dented easier. If it is smaller it will hold up to internal pressure better than a larger tube, granted a larger tube will hold up to external pressure from bending better, but we are talking about internal from the steerer tube.

Kinda like a piston, a smaller piston holds more pressure than a larger one. (that's the best example I can come up with)

It would make sense if they did it to make more surface area so they have more area to weld the other tubes to to make a stonger head junction. But I would imagine the difference would be so small it wouldn't be worth trying to change the industry standard of inch and an 8th.

I mean I'm not saying a 1.5 headtube is bad or anything like that, all I mean is that I want to understand how it all works. So I can learn!!

Or is the 1.5 headtube not that much stronger ....but it allows fork builder to just put a larger steerer tube on their forks to somehow make forks a bit stiffer?

Thanks in advance guys!!

AND I know this has been disgused many times, but I cna not find the exact answer I'm looking for

 

[sub6]

I'd rather let someone like Weagle (an engineer's engineer) answer this but until then, here's the short of it:

A smaller hole is easier to ovalize, because it deforms easier. Your force (a 1.125 headset cup being mashed against ONE SIDE of the hole) is concentrated in a MUCH smaller area than it is with a 1.5" headset cup. Like if you wear ladies' 6" spike heels on soft dirt, you'll sink right in. If you wear dinner plates on your feet, you stay on top of the ground. Less deformation = MORE BETTER.

There are also other issues associated with it. You can use much larger bearings which last longer b/c the force is less concentrated on them. You have a larger area to weld to, and the increased size of the whole structure is much stiffer (although I must admit, HT flex on my 1.125 bikes is hardly losing races for me).

As for the steerer tubes, look at ANY aluminum bike. Do you know the reason why the frame tubes aren't skinny like on a steel bike? It's because Al isn't nearly as stiff as steel is, and if they made them that skinny, the frame would basically be like riding a paper clip. Fatter, thinner tubes are MUCH stiffer. Hence, a fatter steerer tube, with correspondingly large crown, will result in a stiffer fork. End of story.

 

[sub6]

as for the piston analogy - I don't know the FIRST thing about engine engineering, but are you sure that the increased pressure isn't so much an issue of the capabilities of the cylinder bore, but rather that it just ends up being higher pressure since a smaller volume will experience a steeper increase in pressure?

 

[slcpunk21]

Originally posted by sub6
I'd rather let someone like Weagle (an engineer's engineer) answer this but until then, here's the short of it:

A smaller hole is easier to ovalize, because it deforms easier. Your force (a 1.125 headset cup being mashed against ONE SIDE of the hole) is concentrated in a MUCH smaller area than it is with a 1.5" headset cup. Like if you wear ladies' 6" spike heels on soft dirt, you'll sink right in. If you wear dinner plates on your feet, you stay on top of the ground. Less deformation = MORE BETTER.

There are also other issues associated with it. You can use much larger bearings which last longer b/c the force is less concentrated on them. You have a larger area to weld to, and the increased size of the whole structure is much stiffer (although I must admit, HT flex on my 1.125 bikes is hardly losing races for me).

As for the steerer tubes, look at ANY aluminum bike. Do you know the reason why the frame tubes aren't skinny like on a steel bike? It's because Al isn't nearly as stiff as steel is, and if they made them that skinny, the frame would basically be like riding a paper clip. Fatter, thinner tubes are MUCH stiffer. Hence, a fatter steerer tube, with correspondingly large crown, will result in a stiffer fork. End of story.

Ok so I basically answerd my own question? haha.

Ok with the wearing of heals (I hope you don't know that from presonal experience) I know what you mean.... though.

And I've been a bike mech for 8+ years, so I understand about the frames and stuff like that. I already new why the did the steerer tube, just wonderd only about the headtube

I hope you don't mind more questions..... in my mind still with the smaller tube essentially what I think is that when the steerer tube goes to push on the headtube wall it has a smaller area to ovalize due to the fact that the side walls act as support for the front or back wall it's pushing on. But with the 1.5 or larger tube diameter you have a greater span before those side walls support the front or back walls. Again, that's just how my brain thinks of it. I wish I could get a visual or something cause then it would be easier for me to stop thinking like this..haha

Are they then making the walls of the 1.5 tube thicker than the 1.125 head tubes? If they are then this all makes much more sense, and I understand.

Thanks SUB 6 I do appreciate you help!

 

[slcpunk21]

Originally posted by sub6
as for the piston analogy - I don't know the FIRST thing about engine engineering, but are you sure that the increased pressure isn't so much an issue of the capabilities of the cylinder bore, but rather that it just ends up being higher pressure since a smaller volume will experience a steeper increase in pressure?

I was actually thinking of a brake piston..not an engine piston.

But to add to that theory, what about a shock pump versus a tire pump, creates higher pressure. Not saying it deffinately holds more pressure than a larger one. I understand that a shock uses less air volume and needs higher pressure to overcome the linkage system. And a tire pump needs to move more volume Anyways, just thought I'd explain what I was thinking there a bit.

 

[ohio]

Your piston and pump analogy is perfect, you're just looking at it backwards.

Looking at a tire pump vs. a shock pump, for the same amount of force from your arm, a small piston (and the air chamber it's pumping into) sees much higher pressures right?

Well for the same amount of force from a fork, a smaller diameter headtube sees much higher pressures too.


A small piston can handle a lot of pressure, because at that size a lot of pressure doesn't mean a lot of force. But on the case of a headtube we have a FIXED amount of force, and are trying to figure out the pressure. Lower pressure is better.

 

[slcpunk21]

Originally posted by ohio
Your piston and pump analogy is perfect, you're just looking at it backwards.

Looking at a tire pump vs. a shock pump, for the same amount of force from your arm, a small piston (and the air chamber it's pumping into) sees much higher pressures right?

Well for the same amount of force from a fork, a smaller diameter headtube sees much higher pressures too.


A small piston can handle a lot of pressure, because at that size a lot of pressure doesn't mean a lot of force. But on the case of a headtube we have a FIXED amount of force, and are trying to figure out the pressure. Lower pressure is better.

I believe I see where you're coming from... it's kinda starting to all come together between what you and sub 6 said!

I also think part of the problem is that I'm thinking of it as a 1.125 steerer tube in a 1.5 head tube and thus that would ovalize the 1.5 (what ever the actual size is) headtube easier, but I have to keep thinking 1.5 steerer tube in that headtube and thus disperses the load over the entire tube on all the walls, not just the front wall alone.

It's gonna take me a little time to completely put it all together...so once again, thanks so much!

And if anyone else has any ideas shootem this way!


ONE more idea, what about making the steerer tube and crown one piece? bet that would help stiffen things up. No idea how to do that though.

 

[usfddeke]

somewhere along the lines, someone stated the 1.5 HT was 44 percent stronger/stiffer/what have you...
i understand the whole it will deform easyier idea, but its backwards. the wall thickness of the head-tube desn't really matter compared to the diameter of the tube. example of round things in place already. ball bearings. we all use um. we all love them. the bigger they are, the less they wear/break/deform. more metal in the right proportions will do wonders... as for it being accepted into practice who knows.

 

[SK6]

Having done pipe design and engineering for 18 years, It's as simple as this. Smaller the pipe dia, the smaller the wall thickness.

This following chart gives you a better idea.

http://www.interpipe.com/Pipe_Dimensions_and_Weights.htm#10

For example, A 12" pipe has a wall thickness of .75"

So The theory behind the 1.5 head tube just makes logical sense. Thicker wall thickness with minimal weight gain = stronger and more reliable head tube.

I believe whats happened is that everyone is assuming that the 1.5 head tube is the same wall thickness as the standard.

 

[binary visions]

I'm not sure wall thickness really has anything to do with this application. The 1.5 standard has to do with an internal dimension, you can make the headtube walls as thick as you want. For instance, Banshee has enormously thick head tubes - but they aren't 1.5 compatible.

The wall thickness has no effect on a compressive ovalization.

I believe the point of 1.5 is that you can have a LESS wall thickness while still achieving a greater strength (well, that's not the point of it but that's the end result - the Evil headtube has far thinner walls than the Balfa/Banshee ones but is much stronger).

edit: am I missing your point or not understanding something?

 

[SK6]

Originally posted by binary visions
The wall thickness has no effect on a compressive ovalization.

Your kidding right?

 

[SK6]

OK, try this chart as an example. It's easier to read.

http://www.principalmetals.com/utilities/pipechart.htm

 

[binary visions]

Originally posted by sirknight6
Your kidding right?

No, why? If I take a cylinder made of wood and torque a bar in it, simulating the headset pressing on the headtube walls, it will dent and "ovalize". This exact same dent will occur whether the wood is 1/4" thick of 5" thick, and it won't take any more effort on my part when the wood is thicker, as long as the amount of contact area between the headset and the headtube (or bar and wood) is the same.

 

[SK6]

Originally posted by binary visions
No, why? If I take a cylinder made of wood and torque a bar in it, simulating the headset pressing on the headtube walls, it will dent and "ovalize". This exact same dent will occur whether the wood is 1/4" thick of 5" thick, and it won't take any more effort on my part when the wood is thicker, as long as the amount of contact area between the headset and the headtube (or bar and wood) is the same.

I see were your coming from, but I have to disagree. If the wall thickness is greater (refering to pipe) it can handle more pressure and volume. Thats just basic pipe design.

But, I do however have to kill my own argument here with the fact that it's not pipe we're talking about. To effectively determine this, the wall thickness in effect would have to be measured compaired to the standard.

If in fact the wall thickness is thicker, then the additional strength stands so reason. And yes, it would take more pressure to "ovalize" the pipe simply do to the additional mass.

again, based on adding the same exact pressure on the 1.5 as you would the 1.125

 

[SK6]

Originally posted by sub6


A smaller hole is easier to ovalize, because it deforms easier. Your force (a 1.125 headset cup being mashed against ONE SIDE of the hole) is concentrated in a MUCH smaller area than it is with a 1.5" headset cup. Like if you wear ladies' 6" spike heels on soft dirt, you'll sink right in. If you wear dinner plates on your feet, you stay on top of the ground. Less deformation = MORE BETTER.

Here's another way to put it.

 

[binary visions]

Originally posted by sirknight6
I see were your coming from, but I have to disagree. If the wall thickness is greater (refering to pipe) it can handle more pressure and volume. Thats just basic pipe design.

But, I do however have to kill my own argument here with the fact that it's not pipe we're talking about. To effectively determine this, the wall thickness in effect would have to be measured compaired to the standard.

If in fact the wall thickness is thicker, then the additional strength stands so reason. And yes, it would take more pressure to "ovalize" the pipe simply do to the additional mass.

again, based on adding the same exact pressure on the 1.5 as you would the 1.125

Well, this whole issue has been argued a few times on the Downhill board and some people who have done a lot of analysis on this specific issue (that is, not pipes, but headtubes) have stated over and over that the compressive compression failures are not affected by headtube wall thickness. This makes sense to me - I see no reason in anything that I learned my physics classes to believe that more material will prevent it from compressing. Additional mass does not create additional density. The only thing that would help that is a different material (say, a harder aluminum alloy).

Will increased thickness help prevent tensile failure? Yes (question: does anyone know how often a tensile failure of a headtube happens?). Will it increase weldable surface area? Yes. Also, I'm not a welder, but I'm pretty sure it's preferable to weld something to a thicker surface than a thinner one.

I think the issue here is you're looking at pipe design, which is a different type of pressure. Absolutly, thicker pipes can handle more pressure. And if you were to run extremely high pressure water through a headtube, the Banshee one will hold up a lot better than most! It's just not what's happening with the pressures in the headtube.

 

[SK6]

LOL!!! Yeah, I was my own devil's advocate!!!!!

It's a fun debate however!!!!

 

[binary visions]

Originally posted by sirknight6
LOL!!! Yeah, I was my own devil's advocate!!!!!

It's a fun debate however!!!!

Always up for a good debate!

Interesting, though, that something that is clearly so much stronger for one purpose (like the pipes you design), can be so useless for another purpose.

 

[SK6]

Originally posted by binary visions
Always up for a good debate!

Interesting, though, that something that is clearly so much stronger for one purpose (like the pipes you design), can be so useless for another purpose.

Well, I disagree......

 

[D_D]

Originally posted by slcpunk21
And if anyone else has any ideas shootem this way!

Imagine the head tube as a massive solid block with 2 holes in it.

Hole a is a standard head tube with a headset cup in
Hole b is 1.5 with a headset cup.

To ovalise the headtube you need to supply enough force to deform the metal.

If you apply the same ammout or force to both headset cups the one in hole a has less surface area to distribute the force than the one in hole b. Each unit of metal in hole a will have to deal with more force than each unit of metal in hole b because there are less units of metal in contact with the cup in hole a than the cup in hole b but the same ammount of force.

 

[slcpunk21]

Thanks a ton guys!! I'm really starting to understand! The bigger bearing helped me alot to, I didn't think about that aspect of it.

Oh I did think about one thing with the bearing though, a bearing is ment to spin completely. and on bikes it only moves soo much. never really complete a full spin. Well a guy was saying that bearings need to do a full rotation other wise they wear funny and wear faster.

But I can see how having a bigger bearing could help the headsets. And as I have thought about it more and more if you have a bigger tube with a bigger steerer inside it will disperse the hit on more area thus allowing the tube to withstand more. So I think I understand now! To bad I have never trashed a headtube.

Anyways .... Thanks again, and I hope I didn't bore you all with the same subject that has been brought up many times.

Do you think they'll try a 1.5 standard on other bikes besides mtb's? like BMX, ROAD and what not? I see the industry having a hard time with the 1.5 for mtbs just because then it will mean producing something seperate. Oh well it will be interesting to see what happens in coming years.

 

[binary visions]

Originally posted by sirknight6
Well, I disagree......

Don't make me come over there!

 

[binary visions]

Originally posted by slcpunk21
Do you think they'll try a 1.5 standard on other bikes besides mtb's? like BMX, ROAD and what not? I see the industry having a hard time with the 1.5 for mtbs just because then it will mean producing something seperate. Oh well it will be interesting to see what happens in coming years.

It certainly won't happen on road bikes - there is no "problem" to deal with (ever seen an ovalized road bike headtube??). It's not really an issue with cross-sport compatibility, because the parts they produce are so fundamentally different anyway. I mean, the headset for a road bike is different from the one on DH bike, and they are both different from the one on a BMX bike. So they don't have to have a different manufacturing process just because it's a 1.5" headset on a DH bike - it's a different manufacturing process ANYWAY. And people don't put long travel suspension forks on road bikes or BMX bikes, so you don't need steerer tube compatibility there.

Steerer tubes are relatively cheap to produce so that's not really a factor.

I think what we will see is both the 1 1/8" and 1.5" standards stay around for a long time - there won't be a homogenization of the industry. Just like 68mm vs. 73mm bottom bracket shells. There's no reason for XC bikes to end up with 1.5" steerers, nor should cyclocross bikes have it. Wal-mart bike brands certainly aren't going to retool their Taiwan facilities. I think 1.5" will become more and more common but 1 1/8" isn't going anywhere. And I highly doubt that the 1.5 standard will start appearing in other facets of the sport.

 

[SK6]

Originally posted by binary visions
Don't make me come over there!

ROFLMAO!!!!!

 

[KonaDude]

Originally posted by sirknight6
Your kidding right?

Compressive ovalization is different from ovalizing the whole tube. True, a thicker tube is less likely to flare completely (measureable both internall and externally). However, thickness won't affect the metal's resistance to compression under pressure. Only the properties of the metal control that.

Hopefully this clears up the misunderstanding.

 

[johnbryanpeters]

Originally posted by binary visions
...ever seen an ovalized road bike headtube?...

Yes. My commuters all eventually wound up with ovalized head tubes.

As a matter of fact, I just found out that my trusty old three-speed has that problem.

J

 

[binary visions]

Originally posted by johnbryanpeters
Yes. My commuters all eventually wound up with ovalized head tubes.

As a matter of fact, I just found out that my trusty old three-speed has that problem.

J

Ahahaha. Wow, you must be rough on your commuters. But in the end, if you just put a slightly deeper press headset in, it'd solve your problem. 1.5 is certainly not necessary...

Ovalizing road bike headtubes isn't exactly a widespread problem!

 

[shootr]

What I think that you are missing is the actual "why" of the 1.5
You are all skirting the reasoning.
The primary goal of the OnePointFive. is increased stiffness and strength WITHOUT a significant weight penalty.

They are NOT concered with "ovalized" head tubes, in fact the primary impetus has little to do with the headtube itself.
It has to do with the fork
more specifically long travel single crown forks.
The problem with the 1,1/8" steerer is to make it strong enough and stiff enough for a long travel (more than 4") fork it becomes excessively heavy.
This is not a prob with dual crown forks as they place the steerer in double shear, negating the need for a OnePointFive.
an alum. 1 1/8" is way more than strong enough for this application.

Head tube failures themselves are not of major concern, as steer tube failures have much more catastrophic consequences.
There is however a strengh advantage also yeilded by this new standard to the headtube and even more importantly to the headtube's interface with the front triangle, as the massive increase in surface area promotes a better platform for attaching the downtube and top tube (or monocoque), this in turn realizes a stronger and stiffer frame.

but back to the steerer.
as fork travels increased the leverage on the steerer and its crown interface increased, this amount of force now easily exceeds the acceptable limit of the 1 1/8" steerer.
And the industry as a whole acknowledges that you the consumer is only going to want larger and larger single crown forks (ie. the Marz Z150).
So they were left with NO choice, either make stupidly heavy steerers or go larger, they settled on the latter and the reason for One point Five was that was a dimension they felt left them enough room for growth in fork size, without altering the appearance of the current crop of bikes substantially.

I hope that this clears some stuff up, but if you really still have questions just visit One PointFive this is the site that the industry built with each other to actually make this a standard.

 

[Jm_]

My faith in 1.5 is dropping fast. I can't use just any old 1/1/8th fork in it because the 1.5 to 1.125 conversion headset is too damn tall, and things like the fact that the top crown will require some spacers because the 1.5 is too damn wide for the crown, and the fact that the bottom race is convex and takes up a few more precious mm, means that I can't really run the shiver like it is supposed to be run, I have it extended as far as possible, and I only have 7.25" of clearance. I am going to run it like this though, and put a little more oil in it, but its rediculous that I can't run this fork properly on this bike. The head tube(on a medium frame) is too tall, and the 1.5 "conversion" headset is also too tall, especially when you consider how wide the 1.5 is that that all drop crowns won't clear it without spacers under em.

So what is the fix?

 

[shootr]

This is the exact reason that the industry wants to standardize.
If there was (will be) a universal standard, then separate manufacturers would be able to make peices fit without difficulties.
This standard DOES work, but it is still at it's infancy.
that is why current gen forks may have fitment probs in new gen OnePoint Five frames.
I know that this does not help you, now, but eventually this will be a non-issue.
just curious what frame are you experiencing this problem on?
*note this standard is not designed for dual crown arrangements, as I earlier stated it is for single crown long travel forks. Duals see little benefit.

 

[SK6]

I've ridden a 1.5 all summer with the Sherman Breakout. I have to admit and say that the fork itself rocks!!!!

The added stiffnes is noticable, and having 6" in a single crown with the 1.5 is just plush. To be honest, I've had bigger worries on the bike with other componants than the 1.5 head tube and the fork.

Actually, except for standard fork maintainance, which all forks require, it was a put on, dial in, and forget fork. NO Problems whatsoever. NONE.

The added stifness allows me to downhill with it, easily. I'm A big guy, about 220, and the fork doesn't even flinch. Drops are no worries as well.

Me, I like the 1.5 standard.

Just my .02

 

[D_D]

Originally posted by shootr
What I think that you are missing is the actual "why" of the 1.5
You are all skirting the reasoning.
The primary goal of the OnePointFive. is increased stiffness and strength WITHOUT a significant weight penalty.

They are NOT concered with "ovalized" head tubes, in fact the primary impetus has little to do with the headtube itself.
It has to do with the fork
more specifically long travel single crown forks.

My fork/crown interface is plenty stiff enough now and Marzocchi don't think 1.5 is needed for steerer stiffness.

As far as I can see all the major advantages for 1.5 benifit the frame.

There is extra weld area and extra area to reduce compressive ovalisation and more room for more bigger bearings.

So I get a potentially better attached headtube, longer lasing headsets and less chance of ovalising my frame. These would help sell me a 1.5 frame.

I can't personally se the benifit 1.5 provides for forks and how it benifits me.

 

[binary visions]

Originally posted by shootr
<too long to quote>

Personally, I care little for the industry's reasoning for creating this standard, as long as there is a result that benifits me. I am pointing out the benifits that I see in the standard. The increased steerer tube size is only a fringe benifit for me, which I may or may not ever take advantage of, even though I ride a bike with a 1.5 headtube. What IS a benifit is the weldable surface area, resistance to ovalization, frame stiffness, and bearing size. That's all in the headtube.

So, you may love the steerer tube size or whatever, but I am not missing or skirting the point of the 1.5 standard, I'm merely enjoying a benifit that may or may not have been the reason the standard was created.

That's like saying owning a Subaru WRX and liking the all-wheel-drive is missing the "point" of all wheel drive, because it was created to increase traction in adverse conditions, not to improve tire grip and handling for a sports car on smooth pavement.

 

[Joe33]

Ive never ridden a one point five So I'm curious to know if any of you guys out there that do have developed creaks in the crown?

I'm curious because all my previous owned single crowned forks have usally started making noise with in a month of riding. "One Pyslo, two 03 z1s". I didn't expect much from the Psylo, but the Z1s should of held up better. I'm pretty sure that the noise comes from where the stear tube is pressed into the crown. Reason being that after riding with a noisy fork eventually the stearing starts to tighten up on the late part of the rotation and can be controlled by first doing a nose manual to tighten it up then slamming the front end down bringing it back. So possibly with larger diameter tube in there it would hold up longer?

 

[SK6]

Originally posted by Joe33
Ive never ridden a one point five So I'm curious to know if any of you guys out there that do have developed creaks in the crown?

I'm curious because all my previous owned single crowned forks have usally started making noise with in a month of riding. "One Pyslo, two 03 z1s". I didn't expect much from the Psylo, but the Z1s should of held up better. I'm pretty sure that the noise comes from where the stear tube is pressed into the crown. Reason being that after riding with a noisy fork eventually the stearing starts to tighten up on the late part of the rotation and can be controlled by first doing a nose manual to tighten it up then slamming the front end down bringing it back. So possibly with larger diameter tube in there it would hold up longer?

I have a silent head tube. No creaks, no noises whatsoever. And trust me I beat the sh!t out of it this summer. As I've said, I had nothing but luck, and like the 1.5 standard.

Actually, for me, It's the only part of the bike that has not caused me any concern. That equals confindence in the bike for me. Again, no creaking.

Just my .02

 

[D_D]

I think the creaking problem mazocchi forks have it at the crown stanction interface so a bigger steerer tube would make no difference.

Almost all sc forks will start creaking eventually if subjected to enough abuse.

If you are having the headset tightness change when the fork is pushed forward/backwards make sure it's not the headset cups moving in the frame.

 

[shootr]

Originally posted by binary visions
Personally, I care little for the industry's reasoning for creating this standard, as long as there is a result that benifits me. I am pointing out the benifits that I see in the standard.

So, you may love the steerer tube size or whatever, but I am not missing or skirting the point of the 1.5 standard, I'm merely enjoying a benifit that may or may not have been the reason the standard was created.

First let me clarify that I was NOT refering to you or anyone else in particular when I said that the point was being missed.
I was refering in general to the nature of the comments being posted.
The thread began with a query regarding the reasoning for the Onepoint Five.
The answer to that is a stronger steerer.
It matters not that YOU personally may never see this benefit, it is the reason for the standard

But the simple answer to Slcpunk21's question is :
Because it is better

 

[slcpunk21]

Originally posted by shootr

But the simple answer to Slcpunk21's question is :
Because it is better

Is that what she said?

 

[dw]

Originally posted by Jm_
So what is the fix?

A headset with less stack height or a newer model fork.

Not everyone wants to run a 3 year old fork on a brand new frame.

dw

 

[thaflyinfatman]

Originally posted by dw
A headset with less stack height or a newer model fork.

Not everyone wants to run a 3 year old fork on a brand new frame.

dw

*cough* You mean 5 years?