# Differences in carbon layups/manufacturing



## Biercycle (Oct 4, 2014)

I have been doing a lot of research on road bikes and have come across a confusing aspect of the carbon frame world. Several prominent brands have several different carbon frame types and others appear to only have one.

Trek: 300, 400 , 500 series, etc
Specialized: FACT 8r, 9r, 11r, etc
Cervelo: seems to have only one type of carbon
Felt: UHC advanced, performance, etc

Questions
1) What do the different numbered types of carbon layups mean for real world use? Is it simply a matter of weight or are there other elements involved? I am looking for an explanation without the marketing schtick here.

2) Is my observation that Cervelo only has one type of carbon lay up correct, or am I missing something?

3) How much of a difference will these different carbon styles make? I suspect this is a very subjective answer and depends on the rider and experience. I have seen some threads where people seem to fall into two camps: one group says that it doesn't matter much while the other says that anything short of the absolute best current manufacturing product is "crap".

Any opinions or thoughts are much appreciated. Thanks!


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## TricrossRich (Mar 26, 2014)

1. Basically the difference in carbon layup come down to their strength and stiffness. A Specialized 11R is using a higher modulus carbon.. that means it is stiffer, which in turn means they can use less of it to accomplish the same job, making the bike lighter. The downside is that this higher modulus carbon can also be more brittle. I don't know if you're using layup entirely correctly, though. It is my understanding that layup refers to how the different layers are laid on top of each other... carbon has a grain, so to speak, so you want to layer certain areas of the bike a certain way to give strength in some directions, but softness/comfort in others. 

2. No.. I'd guess that Cervelo is using different qualities of carbon, like all manufacturers.. they're just not marketing it.

3. i think its all a matter of preference... having ridden several different bikes... from 8R to SWorks from Specialized, a Scott Addict 20, a Cervelo R5... I can say that they did indeed all FEEL different. Obviously this is a combination of many factors, geometry, components, etc, etc... but it is not marketing hype. There is a difference.

I usually find that the people that say having a light/stiff bike doesn't matter, are the people that are on light/stiff bikes. They are convinced they're fast because of their "motor". The people on heavier/softer bikes have a good motor, but they're convinced that getting a lighter/stiffer bike will make them faster.

It's really all just a matter of perspective... the truth is, you need to be light and powerful to be fast... there's no way around that.


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## Hiro11 (Dec 18, 2010)

Strong opinions to follow. These are just my feelings and should not be interpreted as strictly fact.



Biercycle said:


> 1) What do the different numbered types of carbon layups mean for real world use?


In the real world, to everyday serious cyclists... nothing. Period. Toray makes almost all of the carbon prepreg used by almost every single bicycle manufacturer. This includes everyone from generic Chinese open mold makers to Cervelo. Toray T700 in particular offers an ideal balance between stiffness and strength for bicycle making. T700 is also fairly inexpensive, which is why everyone uses it.


> Is it simply a matter of weight or are there other elements involved?


While it's true that higher modulus carbon fabric will hypothetically allow manufacturers to use less fabric to attain the same level of stiffness, higher modulus is also much more brittle that T700. As a result, regular old T700 still forms the vast, vast majority of the structure even in top end frames. Weight is more driven by the manufacturers ability to eliminate excess epoxy from the mold and less about the carbon layers. Regardless, despite why manufacturers would have you believe, ~200g of frame weight difference is completely meaningless for 99.9999% of riders.


> I am looking for an explanation without the marketing schtick here.


 There is none, I honestly believe this whole "grades of carbon" idea is baloney. Snake oil. It's the manufacturers trying to diversify frames made out of commodity materials. Manufacturers can't diversify based on components as everyone uses the same stuff, they're reduced to making increasingly ridiculous claims about their frames even though everyone uses the same stuff to make frames as well.



> 2) Is my observation that Cervelo only has one type of carbon lay up correct, or am I missing something?


No idea. Note that most pros prefer the cheaper S3 to the S5. note that the even cheaper ("entry level") S2 and S3 are exactly the same frame (different forks). What does that tell you about the relative worth of materials and "layup" to the people who know best, pros?



> 3) How much of a difference will these different carbon styles make? I suspect this is a very subjective answer and depends on the rider and experience. I have seen some threads where people seem to fall into two camps: one group says that it doesn't matter much while the other says that anything short of the absolute best current manufacturing product is "crap".


 I think my opinion here is clear: materials matter little. What matters in ride is frame design, geometry and tire selection. Given the maturity of frame design and the commonly accepted time-tested principles at work here, these things don't cost very much if anything.


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## ericm979 (Jun 26, 2005)

Note that the numbers ("Toray T700" etc) specify only the carbon fibers. Not the layup. Layup is the orientation of the fibers in the various layers. Some frames can have as many as 40 layers of carbon in places, all in a different orientation. Carbon fibers are strong only in tension. The matrix (epoxy in this case) and fiber orientation and tube shape are what give a composite structure it's strength in multiple directions.

I agree that 200g is not going to have a noticeable effect for anyone posting here. Knowing that did not keep me from building a weight weenie bike, though to a reasonable budget and using reliable components.


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## Biercycle (Oct 4, 2014)

Good info here, thanks. I was of the tentative opinion that there was not going to be too much of a difference here, at least not that I would be able to notice, between the various frame types. I am sure there are benefits, but I am not out there competing and will probably not be able to tell. I also know that anything I end up buying will be a vast improvement over my current hybrid.

I think I was using the term "layup" incorrectly. I was trying to refer to whatever you want to call the manufacturing that differentiates the various carbon frame series.

It sounds like the two largest factors are weight and stiffness (with brittleness as a necessary component of the stiffness).


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## Pirx (Aug 9, 2009)

Biercycle said:


> I am looking for an explanation without the marketing schtick here.


Your problem is right there: Once you take the marketing schtick away, you're left with nothing.


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## Trek_5200 (Apr 21, 2013)

With many road bikes of different brands now being built side by side in the same Chinese factory you're only left with basically design and marketing to differentiate them. Ignoring marketing, design means geometry and Carbon frame lay-up, and of the two geometry will have the larger impact on your ride. I agree that most of the Carbon weave is coming from the same plants namely Toray.


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## skitorski (Dec 4, 2012)

ware toray at ??


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## PBL450 (Apr 12, 2014)

skitorski said:


> ware toray at ??


Toray is a Japanese company that produces CF. Considered the best CF by many...


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## stevesbike (Jun 3, 2002)

Just about all of this is nonsense. There are far more differences in bikes today than back in the day when there are a handful of tube sets available. These differences are due to the increased design space allowed by materials (for people who think materials don't matter, they should try to design a cast iron space shuttle). Just about the first thing you learn in Industrial Design is how a "design space" is defined by materials. 

Re the Cervelo S5, the problem wasn't materials - it was design. I've talked with a Garmin rider about the S5 and the problem was the lack of front end stiffness, which resulted in poor descending compared to some of their other models. This was a design issue - trying to minimize drag. Cervelo has now corrected this and is bringing out a redesigned S5 that is much improved in terms of front end stiffness. These are design iterations but you can't make these improvements without using applied material science to use CF grades and layup schedules to achieve the S5 weight benchmarks at the same time. 



Hiro11 said:


> Strong opinions to follow. These are just my feelings and should not be interpreted as strictly fact.
> 
> In the real world, to everyday serious cyclists... nothing. Period. Toray makes almost all of the carbon prepreg used by almost every single bicycle manufacturer. This includes everyone from generic Chinese open mold makers to Cervelo. Toray T700 in particular offers an ideal balance between stiffness and strength for bicycle making. T700 is also fairly inexpensive, which is why everyone uses it. While it's true that higher modulus carbon fabric will hypothetically allow manufacturers to use less fabric to attain the same level of stiffness, higher modulus is also much more brittle that T700. As a result, regular old T700 still forms the vast, vast majority of the structure even in top end frames. Weight is more driven by the manufacturers ability to eliminate excess epoxy from the mold and less about the carbon layers. Regardless, despite why manufacturers would have you believe, ~200g of frame weight difference is completely meaningless for 99.9999% of riders. There is none, I honestly believe this whole "grades of carbon" idea is baloney. Snake oil. It's the manufacturers trying to diversify frames made out of commodity materials. Manufacturers can't diversify based on components as everyone uses the same stuff, they're reduced to making increasingly ridiculous claims about their frames even though everyone uses the same stuff to make frames as well.
> 
> ...


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## robt57 (Jul 23, 2011)

Pirx said:


> Your problem is right there: Once you take the marketing schtick away, you're left with nothing.



Yeah and Googling for data points usually will net 99-44/100s marketing strife, 44/100s, forum user conjecture, and 12/100s actual useful data you may or may not be able to successfully parse as such. ;O


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## Hiro11 (Dec 18, 2010)

stevesbike said:


> Just about all of this is nonsense. There are far more differences in bikes today than back in the day when there are a handful of tube sets available. These differences are due to the increased design space allowed by materials (for people who think materials don't matter, they should try to design a cast iron space shuttle). Just about the first thing you learn in Industrial Design is how a "design space" is defined by materials.


"Nonsense"? Really? You've completely (deliberately?) misinterpreted what I've said. I'm not comparing cast iron to carbon, I'm comparing the various grades of carbon used in bicycles. I believe there's simply no practical difference to these "grades" of carbon given the same frame design. As I already stated, I completely agree that frame design can have a large impact on bike performance. Again, this has little to nothing to do with "carbon grades" 



> Re the Cervelo S5, the problem wasn't materials - it was design. I've talked with a Garmin rider about the S5 and the problem was the lack of front end stiffness, which resulted in poor descending compared to some of their other models. This was a design issue - trying to minimize drag. Cervelo has now corrected this and is bringing out a redesigned S5 that is much improved in terms of front end stiffness. These are design iterations but you can't make these improvements without using applied material science to use CF grades and layup schedules to achieve the S5 weight benchmarks at the same time.


...simply bolstering my point that frame design is what matters, not material.


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## stevesbike (Jun 3, 2002)

it's nonsense to say that frame design can impact performance and that this has nothing to do with carbon grades because the frame design is dependent on the materials that are utilized in the design! I don't know why so many people on this forum think that design is somehow independent of material choice, but it's a bizarre notion. The reason why there are now more engineers in the bike industry is because bike design is now far more complex in terms of possible designs because the material choices and material properties are so much more complex. You say the differences between frames is marketing baloney, but the fact is that frames today are far more varied in their properties than ever before. It's just a false dichotomy to suggest frame design and material choice are independent.

Your claim about the S5 was supposed to imply that pros don't care about materials - they would just as soon ride a cheaper, lower grade carbon. That's not true (for one most of them chose the R5 as an alternative). The point is that materials and design interact - in the case of the S5 the design was flawed, which prompted a redesign that resulted in an improved frame whose properties can't be replicated in a lower grade CF version (you can't get the stiffness of the new front end without adding weight using lower grade cf).







Hiro11 said:


> "Nonsense"? Really? You've completely (deliberately?) misinterpreted what I've said. I'm not comparing cast iron to carbon, I'm comparing the various grades of carbon used in bicycles. I believe there's simply no practical difference to these "grades" of carbon given the same frame design. As I already stated, I completely agree that frame design can have a large impact on bike performance. Again, this has little to nothing to do with "carbon grades"
> 
> ...simply bolstering my point that frame design is what matters, not material.


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## Mr Evil (Aug 12, 2011)

stevesbike said:


> ...for people who think materials don't matter, they should try to design a cast iron space shuttle..


People who think that materials matter need to prove it with data. When people can barely tell the difference between completely different styles of frame, it seems unlikely that changing from one grade of carbon to another will make any real difference beyond the minor difference in weight.


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## robt57 (Jul 23, 2011)

I am reading some carbon nonsense to be sure, not so surprised either. 

I have a 2005 Roubaix, a SL4 2014 Roubaix, and a 2009 Scott Addict LTD, and the wife a Madone. They are all as different in implementation as can be. As different in response and stiffness as an SLX is to a 531C.
Do they fit into a window of similarity as a structure respectively, yeah.
Two examples of tech window width kinda...

The Scott is the best example, arguably the HMX being the 'most' of the tech on a few levels to the Spesh and Trek, even though older. And the cost there-to big time. So how wide is the window between, and more importantly, how wide is the window of nonsense being 'just that', or it being an accurate, albeit subjective.


EDIT: Let me add a pic of todays ride, I would not have ridden my other road bike over this, more so what followed this which was debris city. Pieces of branches big and small all over. My winter bike rides, discs and all. 

Another reasonable purpose related disc road bike justification maybe? The 12 mile of road before I got to this section would not be too much to my liking on either MTB with slicks etc. And the the 12 back home after getting back from where this road took me to a great view point.


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## stevesbike (Jun 3, 2002)

What does perceptible differences have to do with it? Can you perceive any difference between a high fuel economy auto tire and a standard one? Can you perceive a 10 watt reduction in drag at 50 km/hr? Human perception isn't veridical (lots of psychophysics demonstrates that). 

There are lots of ways to objectively measure design differences - Tour magazine does this regularly with the equipment they use to measure frame design differences. You can argue whether design differences matter, but that's an entirely subjective judgment. 



Mr Evil said:


> People who think that materials matter need to prove it with data. When people can barely tell the difference between completely different styles of frame, it seems unlikely that changing from one grade of carbon to another will make any real difference beyond the minor difference in weight.


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## Horze (Mar 12, 2013)

Biercycle said:


> I have been doing a lot of research on road bikes and have come across a confusing aspect of the carbon frame world. Several prominent brands have several different carbon frame types and others appear to only have one.
> 
> Trek: 300, 400 , 500 series, etc
> Specialized: FACT 8r, 9r, 11r, etc
> ...


There is only type of Carbon. It is provided by Toray to all industries comprising of vehicles, aircrafts and components including bicycles.
What you see in the models are different compositions of the same thing. Every brand calls them different things depending on what they've done with it. Usually they will start with the best product that they can make and then see where and how they can cut corners to produce a cheaper product. In the long run this saves the dough in the factory production.


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## Mr Evil (Aug 12, 2011)

stevesbike said:


> What does perceptible differences have to do with it? Can you perceive any difference between a high fuel economy auto tire and a standard one? Can you perceive a 10 watt reduction in drag at 50 km/hr? Human perception isn't veridical (lots of psychophysics demonstrates that).
> 
> There are lots of ways to objectively measure design differences - Tour magazine does this regularly with the equipment they use to measure frame design differences. You can argue whether design differences matter, but that's an entirely subjective judgment.


I would be impressed if you could demonstrate a 10W difference, or any significant performance difference, just from using fibres of a different modulus.


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## den bakker (Nov 13, 2004)

Mr Evil said:


> I would be impressed if you could demonstrate a 10W difference, or any significant performance difference, just from using fibres of a different modulus.


useless statement. 
10W difference under what conditions? 
at a 1500W sprint or a 100W noodle ride?


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## stevesbike (Jun 3, 2002)

I was responding to your claim that a performance difference had to be perceivable for it to matter - I said a 10 watt reduction in drag, which is obviously a design feature. But you can't make a lot of aero shapes, particularly narrow tubes like those Walser used in the model 8, without using carbon and get a stiff frame. Gary Hooker tried but his frames were extremely flexy (and yes that matters on a time trial bike a lot re handling). You can't make Schmolke's TLO 150 gram handlebars without using T1000. 

Re Horze, Toray is a manufacturer, not a carbon type. There are at least 4 main manufacturers that supply the cycling industry...

You can't make a 1000 gram frame like a Velocite Magnus that gets its torsional stiffness numbers without resorting to higher modulus fibers to optimize tube profiles. It's just a truism that design is constrained by material choices and the materials properties determine a design space. Not sure why that's so hard for people to grasp.



Mr Evil said:


> I would be impressed if you could demonstrate a 10W difference, or any significant performance difference, just from using fibres of a different modulus.


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## Mr Evil (Aug 12, 2011)

stevesbike said:


> I was responding to your claim that a performance difference had to be perceivable for it to matter - I said a 10 watt reduction in drag, which is obviously a design feature. But you can't make a lot of aero shapes, particularly narrow tubes like those Walser used in the model 8, without using carbon and get a stiff frame. Gary Hooker tried but his frames were extremely flexy (and yes that matters on a time trial bike a lot re handling). You can't make Schmolke's TLO 150 gram handlebars without using T1000...


Of course carbon allows a lot of shapes that aren't practical in other materials, but the OP was asking about carbon specifically. Yes you can make parts stiffer with higher modulus carbon, but you can do the same with lower modulus carbon by just using more of it. So, aside from weight, there is effectively no difference.


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## Horze (Mar 12, 2013)

And how many types of carbon are there?
The asnwer is Just 1. There is just one type of Carbon.
Unlike alloys which are doped with other elements, Carbon is just Carbon. Actually there are some other tiny variations of Carbon involving nano tubes but not to the extent seen in alloys.

Toray is the main supplier of CF to industry. Then the little factories go on to fabricate their own variations of Composites for whichever product designs they're doing.




Horze said:


> There is only *one* type of carbon. It is provided by Toray...


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## robt57 (Jul 23, 2011)

Horze said:


> Actually there are some other tiny variations of Carbon involving nano tubes but not to the extent seen in alloys.


Isn't this at the semantics level saying this? Not being antagonistic [hopefully]. But being we are getting analogous to alloys et al.

How really is different carbon configs all that different than alloys with 1-2% of different elements in the matrix. Without splitting hairs I mean. Not sure I am getting the point idea across with the words I have chosen exactly.


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## Horze (Mar 12, 2013)

In the same way alloys may be analogous to Aluminum say (an alloy of Aluminum), Composites are analogous to Carbon Fibre.

Even a 'thoroughbred' CF product is really considered to be a Composite because it's doped with epoxy resins to hold the unit together.


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## Pirx (Aug 9, 2009)

stevesbike said:


> You can't make a 1000 gram frame like a Velocite Magnus that gets its torsional stiffness numbers without resorting to higher modulus fibers to optimize tube profiles.


I picked this statement somewhat randomly among a number of similar ones to make the following point:

Yes, it is true that you can have significant differences in stiffness between different kinds of carbon fiber materials, but it really helps to put some numbers on such statements. If we do that, it turns out that the differences in Young's Modulus between realistic candidate materials are of the order of 20% or so, and I won't even go into the consequences for the strength of the respective carbon fiber types. I'll just note in passing that stiffness is not the only parameter that matters; sometimes strength matters too, and some very-high modulus CF materials are significantly less strong that lower-modulus materials.

Anyway, to come back to the question of frame design, for the stiffness of the frame it's both material stiffness (Young's Modulus) and inertial moment of the frame cross sections that matters. Now, it turns out that the latter varies with the _fourth power_ of the transverse dimension (roughly), or in other words, if I increase my tube diameter by 5%, I'll see a 20% increase in frame stiffness. Given that situation, the importance of the Young's Modulus is seen to be a much more moderate one. So, yes, there is an effect, but the required modifications in frame design to make up for a lower Young's Modulus are quite small. 

So, yes, it is absolutely possible to build a stiff frame with lower-modulus CF which will be near-indistinguishable from a frame of identical stiffness built with high-modulus CF.


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## ibericb (Oct 28, 2014)

It is very difficult to generalize over such a varied industry. However, in the case of both Trek and Specialized the different "grades" of carbon-fiber composite reflect the use of different underlying carbon fabric / matrix resin combinations to produce composite materials with different property balances (e.g., stiffness vs. toughness vs. strength vs. weight).

While Toray is the recognized leader in carbon-fiber prepreg materials to bicycle manufacturers, they are not the only supplier. Further, while T700S may be the dominant material sold and utilized on a weight basis, Toray is selling at more than six different materials in their T700, T800 and T1000 families to familiar name bicycle manufacturers. 

For Trek, their OCLV composites currently exist in 5 "grades" (300, 400, ..., 700). As you climb in the series the stiffness to weight ratio increases, which leads to a lower weight part for the same stiffness. Trek also claims higher "vertical compliance" as you advance up the series. Trek illustrates this for the consumer market in a series of oversimplified slides you can see here

Those higher series OCLV composite parts are more expensive because (1.) the underlying prepreg fabric is more expensive, and (2.) the lower areal weight fabrics are much trickier to work with. 

You might also be interested in a white paper released by Specialized in 2005 titled, "Taking the Witchcraft Out Of Advanced Composite Bicycle Frames".


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## Pirx (Aug 9, 2009)

ibericb said:


> For Trek, their OCLV composites currently exist in 5 "grades" (300, 400, ..., 700). As you climb in the series the stiffness to weight ratio increases, which leads to a lower weight part for the same stiffness.


The stiffness increases, but not by much. Weight of the material is not a factor, since it's almost exactly constant across the materials used.



ibericb said:


> Trek also claims higher "vertical compliance" as you advance up the series.


I have a hard time believing they would claim anything as stupid as that. "Vertical compliance" has nothing whatsoever to do with the material, and everything with the design (geometry). Looking at the slides you must be referring to it does appear that indeed they are talking about geometry in this context, not material.



ibericb said:


> Those higher series OCLV composite parts are more expensive because (1.) the underlying prepreg fabric is more expensive, and (2.) the lower areal weight fabrics are much trickier to work with.


Yep, sure. Makes maybe a difference of 50 bucks in cost to Trek, for a difference in selling price of a thousand bucks. Like I said before, the margins for those high-end components are simply insane. Well, once you understand the laws of this market, of course, it's what you would expect. The stuff costs what the market will bear, as always...


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## ibericb (Oct 28, 2014)

Pirx said:


> The stiffness increases, but not by much. Weight of the material is not a factor, since it's almost exactly constant across the materials used.


According to Trek's published numbers, the stiffness:weight ratio difference between their 300 vs 700 series OCLV layups is about 35%. For weight weenies in their market, that may be a bit of a deal. However, in a total bike build it's really a small amount (about 350 grams for the frame out of something like 8800 grams for the finished bike, or about 4% of finished bike weight).




> I have a hard time believing they would claim anything as stupid as that. "Vertical compliance" has nothing whatsoever to do with the material, and everything with the design (geometry). Looking at the slides you must be referring to it does appear that indeed they are talking about geometry in this context, not material.


Compliance (yielding under load) has a lot to do with net material properties. If you don't believe that build the same geometry in steel, Al and carbon fiber. In Trek's frames it is likely more a result of the layup dictated by strength requirements, and playing the differences between tensile vs. flexural modulus. The slides I am referring to compare only different OCLV carbon "grades", and reflect a relative increase in vertical compliance of 140% in going from 300 to 700 series OCLV carbon composite.





> Yep, sure. Makes maybe a difference of 50 bucks in cost to Trek, for a difference in selling price of a thousand bucks. Like I said before, the margins for those high-end components are simply insane. Well, once you understand the laws of this market, of course, it's what you would expect. The stuff costs what the market will bear, as always...


Much of the difference is pricing as you go up the series in Trek frames comes with how they equip those higher priced models. As a comparison, consider a 2014 Damone 4.7 vs a 2015 5.2. The price difference between the two is $679. For that you get a 500 series OCLV frame with a seat mast design and internal frame cable routing, an $80 step up in tires, a $50 step-up in handlebar, and a $20 step-up in seat. Backing out the component upgrades (~$150), you pay ~$529 for the frame upgrade and what it brings (weight, cable routing, seat mast, ride).


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## stevesbike (Jun 3, 2002)

The trouble with this is that you are obviously increasing the surface area of the tube, which means you either have to use the same amount of material but make thinner walled tubes (which offsets the gains in diameter to some extent) or keep the thickness constant and so use more material, hence the additional weight to get the same stiffness numbers. Ultimately, there's a practical limit to this, as makers discovered with alloys - I remember Deda tubesets (I think) that were so thin walled that even a small object could cause a bad ding. So the frames may be indistinguishable in terms of stiffness but not weight. That's the whole point of materials constraining design.




Pirx said:


> I picked this statement somewhat randomly among a number of similar ones to make the following point:
> 
> Yes, it is true that you can have significant differences in stiffness between different kinds of carbon fiber materials, but it really helps to put some numbers on such statements. If we do that, it turns out that the differences in Young's Modulus between realistic candidate materials are of the order of 20% or so, and I won't even go into the consequences for the strength of the respective carbon fiber types. I'll just note in passing that stiffness is not the only parameter that matters; sometimes strength matters too, and some very-high modulus CF materials are significantly less strong that lower-modulus materials.
> 
> ...


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## Pirx (Aug 9, 2009)

ibericb said:


> According to Trek's published numbers, the stiffness:weight ratio difference between their 300 vs 700 series OCLV layups is about 35%.


You need to look at their marketing drivel a little more closely in order to understand the facts behind it. Specifically, when they talk about weight advantages, they are really referring to what they call "areal weight" (weight per area of the sheet), which is not at all the same as the density of the material. If you have the background to understand what my statement above means then that's all I need to say.



ibericb said:


> Compliance (yielding under load) has a lot to do with net material properties.


Obviously, but they specifically talk about _vertical_ compliance, not about compliance in general. The former as distinguished from the latter has nothing to do with material.



ibericb said:


> If you don't believe that build the same geometry in steel, Al and carbon fiber.


Please. Do yourself a favor and do not try to educate me. Nobody in his right mind would build "the same geometry" when using wildly different materials.



ibericb said:


> In Trek's frames it is likely more a result of the layup dictated by strength requirements, and playing the differences between tensile vs. flexural modulus.


Heheh. Nice combination of fantasy and idle speculation. You know nothing about the likelihood or not of whatever went into the design of these frames, so don't pretend you do. By all means, feel free to present rigorous definitions of the terms "tensile modulus" and "flexural modulus". From there, let us know what exactly those differences are that you are alluding to. Not to be misunderstood, I'm not being facetious here: I'm just trying to get you to back off from the marketing mumbo-jumbo and talk about the actual physics behind these terms.



ibericb said:


> The slides I am referring to compare only different OCLV carbon "grades", and reflect a relative increase in vertical compliance of 140% in going from 300 to 700 series OCLV carbon composite.


Which are these? The ones I looked at all note the differences in frame _geometry_. I note that the difference you quote is physically impossible based on the material difference alone: Material stiffness differences are much less than that, even just taking Trek's slides themselves (that I believe overstate the difference).


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## Pirx (Aug 9, 2009)

stevesbike said:


> The trouble with this is that you are obviously increasing the surface area of the tube, which means you either have to use the same amount of material but make thinner walled tubes (which offsets the gains in diameter to some extent) or keep the thickness constant and so use more material, hence the additional weight to get the same stiffness numbers. Ultimately, there's a practical limit to this, as makers discovered with alloys - I remember Deda tubesets (I think) that were so thin walled that even a small object could cause a bad ding. So the frames may be indistinguishable in terms of stiffness but not weight. That's the whole point of materials constraining design.


Well, yes, but given the fact that in most areas of the frame the main design driver is indeed stiffness (and not strength), I could indeed make my walls thinner and this way keep my weight constant. Remember it's only a few percent that are needed here. At some point you'll have to deal with the kind of issues you mention, however, plus eventually shell instabilities (buckling), so you are absolutely right, things are not necessary that simple.

Just to be clear, I am not disputing your more general point at all: Yes, absolutely, material, and material properties do make a difference. However, once we talk much more narrowly about the specific differences between the different grades of carbon available, those differences do become quite small. But again, while they are small differences, they do play a role.


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## ibericb (Oct 28, 2014)

Pirx said:


> You need to look at their marketing drivel a little more closely in order to understand the facts behind it. Specifically, when they talk about weight advantages, they are really referring to what they call "areal weight" (weight per area of the sheet), which is not at all the same as the density of the material. If you have the background to understand what my statement above means then that's all I need to say.



Trek talks both about areal weight, and about net composite stiffness:weight. I understand both quite well, as well as the difference.





> Obviously, but they specifically talk about _vertical_ compliance, not about compliance in general. The former as distinguished from the latter has nothing to do with material.


If you will review my first comment here, it specifically noted _vertical compliance_. Did you miss that ? Interesting, because they make their point comparing solely the difference based upon the frame material designation.




> Heheh. Nice combination of fantasy and idle speculation. You know nothing about the likelihood or not of whatever went into the design of these frames, so don't pretend you do. By all means, feel free to present rigorous definitions of the terms "tensile modulus" and "flexural modulus". From there, let us know what exactly those differences are that you are alluding to. Not to be misunderstood, I'm not being facetious here: I'm just trying to get you to back off from the marketing mumbo-jumbo and talk about the actual physics behind these terms.


I'll forego the invitation as this isn't the place. Having spent 30 years in materials research, including long periods running sizable R&D programs in advanced composites for aerospace, I fully know the meanings of the terms. This is a cycling forum, not a materials science forum, so let's keep it relevant.





> Which are these? The ones I looked at all note the differences in frame _geometry_. I note that the difference you quote is physically impossible based on the material difference alone: Material stiffness differences are much less than that, even just taking Trek's slides themselves (that I believe overstate the difference).



Under Features click on the OCLV feature pic to Learn More. There you will see Trek's representations for the different composite series basic features. Going a step further, note that Trek's general frame geometries (not tube geometries) are identical for a given model frame size regardless of whether it is a 300 series OCLV or 700 series OCLV frame. You can see that in both the Domane and Emonda frames. No doubt, the dimensions of the frame members will vary as layups change with material changes, but the net bike geometries remain identical.

Final comment - if you want to quibble with Trek on their material representations, please take it up with them. I am using their representations as they have published them. It was an attempt at a lay explanation to the OP question about what do the differences mean.


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## stevesbike (Jun 3, 2002)

I don't think we're disagreeing, though, the question of what's a small difference is one of perspective - a 300 gram reduction in frame weight while keeping torsional stiffness constant may sound small, but if that represents a 30% overall reduction in weight that's a significant improvement from a design standpoint. Similar improvements in other design areas would be enormously significant (e.g., 30% reduction in aircraft weight, improved energy efficiency etc). 



Pirx said:


> Just to be clear, I am not disputing your more general point at all: Yes, absolutely, material, and material properties do make a difference. However, once we talk much more narrowly about the specific differences between the different grades of carbon available, those differences do become quite small. But again, while they are small differences, they do play a role.


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## Pirx (Aug 9, 2009)

ibericb said:


> I am using their representations as they have published them. It was an attempt at a lay explanation to the OP question about what do the differences mean.


Understood.


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## ibericb (Oct 28, 2014)

So, back to the OP's first question. "_What do the different numbered types of carbon layups mean for real world use? Is it simply a matter of weight or are there other elements involved? I am looking for an explanation without the marketing schtick here.", _my take is it is pretty much about weight, and just frame weight at that. 

Talking just about carbon composite differences how big does that get? Well in the range of Trek's options it should amount to around 300 grams in a 56 cm frame size. How big a percentage is that? At the extreme, which would be an Emonda with a 700 series frame weight of 690 gram in a 10.25 lb (4654 gram) total bike weight (for a price of $15,750), that would amount to a change of about 6.4% total weight. That's the extreme difference. More practically it is much smaller than that, around 2-4% weight reduction possible over the extremes of Trek's C-fiber composite road frames for a given model/size.


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## scott967 (Apr 26, 2012)

Horze said:


> And how many types of carbon are there?
> The asnwer is Just 1. There is just one type of Carbon.
> Unlike alloys which are doped with other elements, Carbon is just Carbon. Actually there are some other tiny variations of Carbon involving nano tubes but not to the extent seen in alloys.
> 
> Toray is the main supplier of CF to industry. Then the little factories go on to fabricate their own variations of Composites for whichever product designs they're doing.


I think there are 3 types of carbon fiber in commercial use, but PAN-derived carbon fiber is used in bicycles. Toray makes various PAN carbon fiber with different tensile strength and modulus, as does Mitsubishi Rayon and Toho Tenax, among others. But carbon fiber is delivered for bicycle applications I think mainly as untwisted yarn (tow) with various filament counts 1k-12k, so that is a difference. Then the carbon tow have to be made into appropriate reinforcement such as unidirectional (roving) and bidirectional (fabric), fabric using several weaves which make a difference. Finally the reinforcement must be combined with a matrix, in the case of bicycle I think only epoxy is used, but I suppose there are different formulations of epoxy that are combined for use by the bicycle manufacturer and delivered as "prepreg". There are different companies involved in the various intermediate steps and there seems to be quite a bit of cross-supply. 

ISTR some photos of a Chinese factory (maybe one that supplies Dengfu?) that showed some raw prepreg that was labeled as "SK Chem" which is a Korean company that I believe sources its carbon from Mitsubishi Rayon.

scott s.
.


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## SwiftSolo (Jun 7, 2008)

I think it is important to realize that there are two important elements to carbon layup (methods and workmanship notwithstanding). That is the carbon itself and the matrix (epoxy). Both are evolving fairly rapidly due to aerospace industry demands.

That being said, the rate at which such improvements impact bicycles has slowed dramatically and are becoming less significant. Localized layup design (structural) continues to improve more significantly than either carbon or the matrix at this point. The search for that magic blend of layup and localized layup design that will produce the bike with the best vertical compliance to loads generated from below combined with the best lateral and vertical stiffness to counter pedaling loads continues to get a bit closer. 

In reality, road bike frame improvement is slowing almost to a stop as there is little that can be done with the currently accepted design. Mountain bikes have the advantage of shocks with inertia valves that can isolate terrain loading from pedaling loads. At the current state of road bike design, I think that buying a fairly state of the art carbon frame combined with good wheels with rims at or above 24mm in width and 25 to 27mm tires is about as good as it gets for ride quality/efficiency on most roads.


Biercycle said:


> I have been doing a lot of research on road bikes and have come across a confusing aspect of the carbon frame world. Several prominent brands have several different carbon frame types and others appear to only have one.
> 
> Trek: 300, 400 , 500 series, etc
> Specialized: FACT 8r, 9r, 11r, etc
> ...


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## ibericb (Oct 28, 2014)

> In reality, road bike frame improvement is slowing almost to a stop as there is little that can be done with the currently accepted design.


I suspect you're right about frames. Trek claims 690 g for the 56 cm Emonda 10 frame/fork, and 725 g for the Madone 7 series. Both of those have a lighter frame+fork combination than the record holding road bike lightweight of ~850 g. It would seem that the future of further weight reductions for road bikes will be found in all the components that get attached to the frames.


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## goodboyr (Apr 19, 2006)

Those are frame only numbers.


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## ibericb (Oct 28, 2014)

Yep - thought I made that abundantly clear.

For total bike that record holder came in at ~2800 g. Trek's Emonda 10 SLR, which felt like a feather when I hoisted it in my hand, tips the scale at ~4654 g, with a frame+fork that is about 160 g lighter. That means that Mai lightweight enjoys something like a 2kg advantage due to the sum of the component weights.


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## Pirx (Aug 9, 2009)

No, I think the point of the poster above was that your numbers are for the frame only, not frame+fork. I believe he's correct.


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## ibericb (Oct 28, 2014)

Nope, I don't think so.

The Mai lightweight specs are stated in the article linked previously:
Frame = 642.5g
Fork = 185.9 (also cited in various other reference articles about the bike).
Those two numbers add up to 828.4 g
Separately the same article cites a frame weighing 873 g, which in light of other published articles about he same bike would appear to be the assembled frame + fork + a bit more. Another article detailed the various component weights, including headset at 18.9 g. I added that to the 828.4 and rounded to 850.

For Trek it is plainly clear for the Emonda. For the SLR 10 features Trek states the following: 

_"Frame weight comparison 
__Weights are based off current mass production competitor 56cm painted frame or bike at time of publication. We weighed all bikes and frames on the same UWE HS-15k hanging scale and published either the competitor’s claimed weight or the competitor’s weighed weight, whichever was lightest."_

In that comparison Trek cites 690 g for the Emonda SLR 10 (vs. 710 for the Cannondale Super 6 and 897 for the S_Works Tarmac SL4). For the Madone, Trek cites 725 g, with an image of frame plus fork for the Madone 7. In my experience looking at Trek bikes, they typically combine frame + fork in any weight specs. If they differed in those citations, it would be unusual from what I have encountered in the past.

Edit added - According to Velo News, the 690 g Emonda weight also includes the 50 g seatmast. Separately, the SLR 10 fork has been reported at a weight of 280 g. If 690 is indeed frame only, then the combined frame + fork weight (with seatmast) would come in at 970 g.


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## Pirx (Aug 9, 2009)

Hmm, yes, I searched around a little, and it appears you may be right, although that's not that easy to figure out.


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## ibericb (Oct 28, 2014)

No, it's not in the Trek case. 

Let me offer the following from the Australian source CYCLINGTIPS, which I believe is insightful in what Trek has been able to do with the OCLV carbon fiber composite series. A July article about the Emonda gave the following weight specs for three different versions of the Emonda (SLR, SL and S), all for painted 56 cm frames:

OCLV 700 - Emonda SLR: frame 690 g/ Fork 280 g</SPAN>
OCLV 500 – Emonda SL: frame 1050 g / Fork 358 g</SPAN>
OCLV 300 – Emonda S: frame 1220 g / Fork 518 g

Using the OCLV 300 Emonda S as a base, I come up with the following weight reductions for frame and fork as cited in the article:
OCLV 500: frame = -170 g (14%) / fork =-160 g (31%)</SPAN>
OCLV 700: frame = -530 g (43%) / fork = - 238 g (45%)</SPAN>

As I noted previously, Trek maintains the same bicycle geometry for the same size across the different versions. Thus, those weight reductions in moving from 300 up to 700 should reflect that from just the frame composite materials alone. In going from OCLV 300 to 700 Trek achieved a 43% reduction in frame weight and a 45% reduction in fork weight. Assuming that Trek didn't want to sacrifice cycling performance or ride quality as the price tag increases (appreciably), I find that pretty impressive for a production bicycle manufacturer.

That said, it's still not clear to me if the 690 g (as well as those of the others in the Emonda lineup) include the fork weight, or not. I can find out without much effort, but to my thinking it's not really the issue or question. The question raised was about what do the different designations mean, and is there anything significant other than weight.
</SPAN>


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## goodboyr (Apr 19, 2006)

Its clear to me.....690 is frame only....


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## Horze (Mar 12, 2013)

scott967 said:


> I think there are 3 types of carbon fiber in commercial use, but PAN-derived carbon fiber is used in bicycles. Toray makes various PAN carbon fiber with different tensile strength and modulus, as does Mitsubishi Rayon and Toho Tenax, among others. But carbon fiber is delivered for bicycle applications I think mainly as untwisted yarn (tow) with various filament counts 1k-12k, so that is a difference. Then the carbon tow have to be made into appropriate reinforcement such as unidirectional (roving) and bidirectional (fabric), fabric using several weaves which make a difference. Finally the reinforcement must be combined with a matrix, in the case of bicycle I think only epoxy is used, but I suppose there are different formulations of epoxy that are combined for use by the bicycle manufacturer and delivered as "prepreg". There are different companies involved in the various intermediate steps and there seems to be quite a bit of cross-supply.
> 
> ISTR some photos of a Chinese factory (maybe one that supplies Dengfu?) that showed some raw prepreg that was labeled as "SK Chem" which is a Korean company that I believe sources its carbon from Mitsubishi Rayon.
> 
> ...



What you're referring to is the base polymer from which of-course it is made to consist of strands of fibres of carbon atoms. All carbon is derived out of a base polymer. The point I was making, the carbon itself is a unitary material. But there are many, many scales at which the Composite is derived from the underlying material. The moment you alter the underlying Carbon material it becomes a Composite. You are correct by altering the weave patterns and shaping of the Carbon it is possible to change the overall Modulus.

The Polyacrylonitrile (PAN) is just the filament, which is a synthetic carrier of the material. This can in principal be any polymer, or synthetic polymer for that matter. The carbonisation of these filaments leaves the residual Carbon Fibre which is what industry works with.





--
In the beginning God created the Heaven and the Earth...


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## Biercycle (Oct 4, 2014)

That is quite a lot of interesting information. It seems increasingly clear to me that the more you spend on a bicycle, whether it be frame or components, the primary benefit is weight savings with a certain amount of durability (to a point). I am going to guess that, being someone who has never owned a carbon bike and never owned a road bike, the differences in carbon will be minimal to non-existent in terms of my perception of how the bike rides. Additionally, being a fairly larger than average male (6'5" and 225 lbs) the weight savings of higher end carbon frames will be negligible compared to the weight savings I can shave off my body simply by riding more. Maybe once I have lost weight equivalent to how much my bicycle will weight I can consider a better carbon frame, lol.

Im glad Pirx and ibericb were able to work out their differences. There was a lot of informative stuff in that back and forth. So thanks for the minor deviation.


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## ibericb (Oct 28, 2014)

Collegial discussion is usually good, as it has been here.

A significant driver of road bike evolution has been weight reduction. As you go up in a series a major focus of the big-name manufacturers has been to lower weight without compromising and often improving ride performance. As SwiftSolo pointed out, manufacturers have about come to a limit in what they can do with frames without compromising what a frame is supposed to do functionally. From their they turn to continuing their drive via components (e.g., 105 -> Ultegra ->DuraAce, carbon wheelsets, etc.), which is where a lot of the added expense comes from.

In the practical world weight is an issue only when you need to change speed (acceleration), or you need to fight gravity-induced changes in speed (climbs). For the average non-competitive rider it is grossly over-rated in importance. But it sells, largely because of the importance it has for competitive 20-somehting 150 lb cyclists who win or loose by seconds, and how they inspire the rest of us. For the rest of us, as you note, we would be generally better served focusing on our own weight, and I will add our aero profiles.


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## ibericb (Oct 28, 2014)

And you are indeed, correct (confirmed with Trek this morning). 690 g is the painted 56 cm frame sans fork, the fork with 235 mm steerer adds 280g, for a total of 970 g frame + fork.

That then gives the total one-off Mia lightweight an approximate frame + fork advantage of ~140 g, and a net component advantage of 1710 g.


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## goodboyr (Apr 19, 2006)

May as well include the Cervelo RCA in this compare.


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## aclinjury (Sep 12, 2011)

at the end of the day, I reckon the level of differences between the carbon composites and frame designs between the big bike manufacturers (Specialized, Cervelo, Trek, Cdale, Colanago, Pina, etc) are analogous to the differences between peanut butter, sandwiches, and milk sold from the major supermarkets like Vons, Albertson, Ralphs, Costco, Walmart, etc. Zilch, zero, nada.

Now when i start to see pro races won and/or lost due to one frame having a "better" carbon composite or design, then I will start to take notice. Until then, discussion of carbon fiber is mostly academic and marketing. Interesting nonetheless though.


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## Pirx (Aug 9, 2009)

aclinjury said:


> I reckon the level of differences between the carbon composites and frame designs between the big bike manufacturers (Specialized, Cervelo, Trek, Cdale, Colanago, Pina, etc) are analogous to the differences between peanut butter, sandwiches, and milk sold from the major supermarkets like Vons, Albertson, Ralphs, Costco, Walmart, etc. Zilch, zero, nada.


That's an apt comparison. In short, it doesn't effin' matter what frame you buy, as long as it fits and you like it.


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## mambo (Jul 29, 2012)

As Pirx says, the most important factor in choosing a frame is that it should fit you correctly - EVERYTHING else is secondary.


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## ibericb (Oct 28, 2014)

+1 for fit.


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## Horze (Mar 12, 2013)

No way has the industry reached a crescendo in carbon fibre or alloy frames for that matter.
There is always room to improve, To make fine adjustments each time. It's always little little increments. 
Over a 10 year or so life cycle you might find a bike model is unrecongnizable from the previous generation. But then again, the increments are again very to and fro. One step forwards, one step sideways, one step backwards, one step forwards.

Alloy frame still beats Carbon in lightning speed responsiveness. The positive attribute of a Carbon frame that gives it a softer ride quality is also what lets it down in how reactive a CF frame feels. The old adage that Carbon feels dead still seems true to this day. Good alloy frames are still more reactive compared to Carbon. And this has to do with the speed at which an impulse travels across an alloy lattice versus carbon (really it's a Composite structure). It's akin to mechanical conductivity of the material. The speed of impulse is typically sonic but of-course depends on the empty spaces inside the chemical configuration of the material as to how much of the transient resonance gets propagated.


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## aclinjury (Sep 12, 2011)

Horze said:


> No way has the industry reached a crescendo in carbon fibre or alloy frames for that matter.
> There is always room to improve, To make fine adjustments each time. It's always little little increments.
> Over a 10 year or so life cycle you might find a bike model is unrecongnizable from the previous generation. But then again, the increments are again very to and fro. One step forwards, one step sideways, one step backwards, one step forwards.
> 
> Alloy frame still beats Carbon in lightning speed responsiveness. The positive attribute of a Carbon frame that gives it a softer ride quality is also what lets it down in how reactive a CF frame feels. The old adage that Carbon feels dead still seems true to this day. Good alloy frames are still more reactive compared to Carbon. And this has to do with the speed at which an impulse travels across an alloy lattice versus carbon (really it's a Composite structure). It's akin to mechanical conductivity of the material. The speed of impulse is typically sonic but of-course depends on the empty spaces inside the chemical configuration of the material as to how much of the transient resonance gets propagated.


hmm, many interesting statements there.

I'd say that carbon fiber application in the bicycle industry has pretty much climaxed. When the Chinese are getting into something, you know that technology has climaxed.

but I will agree with you that alloys still offer better overall responsiveness.

Does anyone in here follow motogp? GP motorcycles have their swingarms made from alloy. Then Ducati, who for a brief time, tried a carbon swingarm. In theory, carbon fiber should have allowed Ducati to create a swingarm that is optimal in handling the massive power produced at the rear wheel when the bike is straightup and accelerating hard, *AND *at the same time allow enough lateral flex when the motorcycle is leant over in a corner. In theory. But in practice, it made the Duc ragged to ride, ragged while hard on gas and offer nothing but numbness (ie., low traction feedback to the rider) while in corner. Sure Casey Stoner won on it, but it was a one hit wonder, and Stoner it always looked ragged on that thing. No other rider could ride it. In the meantime, Honda and Yamaha using alloy is able to offer many riders a competitive package right off the bat, using alloy. There is something about a metal frame that when it flexes or hit a bump, it doesn't become unsettled like a carbon.


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## Pirx (Aug 9, 2009)

Now if only anybody in this world could give us a definition of the quantity designated as "responsiveness" in the above two posts, together with a way to measure this elusive quantity, then we might in fact have a way to test some of these interesting statements. As it is, those wonderful statements are nothing but lukewarm air. 

As for the "speed at which an impulse travels across an alloy lattice versus carbon", that's pure and unadulterated nonsense. Yes, those speeds will be different but, no, those speeds are so high in either case that it is completely and utterly impossible for a human being to perceive any difference at all: It's roughly 6,000 m/sec in aluminum alloy, and "only" 3,000 m/sec in your typical carbon or glass fiber composite. So, at the very least, ten times the speed of sound in air...


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## aclinjury (Sep 12, 2011)

I was going to ask the same question, define responsiveness. But I didn't bother asking because I knew there would be no one absolute answer. The criteria involved in what makes a bike responsive varry from frame design to material, to tire, tire pressure, to how the rider adapt. Way way too many variables to even fathom in the scope of this thread. Even in Motogp, top level engineers and mechanics often cannot recreate/make the same motorcycle response exactly as the rider wants it, for every track. But it doesn't mean they don't have some general ideas they want to try. And they have the latest in data telemetry at their disposal, and that's pretty much the best they can do. Internet posters on RBR, get real.

But... that doesn't mean anyone interested should stop trying do find what makes a bike response. Let the people talk about it, maybe something will come out of it. Read every sportbike forum, guys talking about responsiveness although nobody know exactly how it is. While there is no absolute definition, there are trend, rider experience. Lukewarm yes, not scientific, but it's best we've got.


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## mambo (Jul 29, 2012)

Horze said:


> No way has the industry reached a crescendo in carbon fibre or alloy frames for that matter.
> There is always room to improve, To make fine adjustments each time. It's always little little increments.
> Over a 10 year or so life cycle you might find a bike model is unrecongnizable from the previous generation. But then again, the increments are again very to and fro. One step forwards, one step sideways, one step backwards, one step forwards.
> 
> Alloy frame still beats Carbon in lightning speed responsiveness. The positive attribute of a Carbon frame that gives it a softer ride quality is also what lets it down in how reactive a CF frame feels. The old adage that Carbon feels dead still seems true to this day. Good alloy frames are still more reactive compared to Carbon. And this has to do with the speed at which an impulse travels across an alloy lattice versus carbon (really it's a Composite structure). It's akin to mechanical conductivity of the material. The speed of impulse is typically sonic but of-course depends on the empty spaces inside the chemical configuration of the material as to how much of the transient resonance gets propagated.


I agree. Carbon fibre is still in a state of improvement and with increased computer power and knowledge will continue to do so. There is a huge improvement still to be made in the epoxy's that bind it together as well and many seem to forget the crucial role these play. 

However I have to disagree with your comments regarding carbon v's alloy frames

Carbon allows you to make a frame that is more than acceptably stiff but is ALSO very comfortable. An equally stiff alloy frame will be much less comfortable as you can't fine tune it to the N'th degree as you can a carbon frame.

One has to bear in mind that carbon layups allow you to dial in the lateral stiffness AND the vertical compliance in a way that alloy's don't. What I assume you mean as a loss of responsiveness is not really the case. The carbon frame will flex to make the ride more comfortable, which you may interpret as a loss of responsiveness, but will not flex significantly under lateral loads which IS the responsiveness that a rider wants.

If your statement regarding responsiveness were strictly true, we would all be buying $5,000 alloy rather than CF frames.


Many of the changes you see in bike models are not necessarily improvements but rather differentiating cosmetic alterations.


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## ibericb (Oct 28, 2014)

Generally, agree with you mambo.

The net differences in both feel and performance arising from any material use in a bicycle frame will be largely determined by design. Those design parameters include things like "tube" shape and dimensions, as well as traditional frame geometry measures.


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## mambo (Jul 29, 2012)

Oh no ibericb...don't get me started on tube shapes... I can feel a sermon coming on here, because unless you are looking for aero qualities, there is only one single tube shape that is best for the main triangle!


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## ibericb (Oct 28, 2014)

Are you thinking isotropic materials (e.g. metals)? What about butting, and internal reinforcing structures in otherwise apparent round tubes? "Tube" (or member) shape and design has a huge influence on resulting physical properties and qualities derived from a frame.


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## mambo (Jul 29, 2012)

I don't get too high tech, I leave those bits to my designers. Simple round tube shapes are structurally stronger and as smaller tubes can be used, lighter.


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## Horze (Mar 12, 2013)

Several points.

Responsivenes can be defined as how much you feel connected with the machine. Namely how quickly it moves OR gives "the perception" of movement when you apply some impulse.

Responsiveness is not stiffness. Let's be absoluetly clear about this. Carbon frames are plenty stiff. Alloy is not stiff but it is a light material. Alloy frames are made stiff by using a relatively huge amount of it (and of-course shaping). Regardless of butting or shaping an alloy frame, the shape doesn't affect how responsive it's going to feel. Responsiveness is due to the intrinsic property of the material.

Of-course Carbon rides great but Aluminum has that quick feel which Carbon lacks.


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## mambo (Jul 29, 2012)

That depends on how you define responsiveness of course! Some people interpret responsiveness as the handling of the bike, which is as much or more to do with the frame geometry as any material used. Other define it as how quickly a bike reacts to the input of power on the pedals.

I also think that stiffness does have a lot to do with responsiveness, in that a stiffer frame will respond more quickly to input.

I'm sorry, but I do disagree with the statement regarding tube shape not affecting how responsive or not a bike may be. Using non-round tube shapes generally increases the weight, as being less stiff, more material has to be used to compensate for the lack of stiffness of those tube shapes (as well as BB's having to be larger to not only accommodate those larger diameter tubes but to help compensate for the inherent lack of stiffness they bring to a frame design). The heavier a bike is the slower it is to respond - in some riders interpretation.

A well designed and built carbon frame will feel as quick as an aluminium frame. But again it depends on your interpretation of quick! Because carbon layups and mixing different moduli means you can dampen vibrations out with carbon, perhaps that quickness you sense from aluminium frames is more about the transmission of road surface vibrations through the frame. I still own a Klein Quantum Pro - probably one of the benchmarks in aluminium stiffness. My all singing all dancing carbon frame, however is just as stiff and responsive but feels less "quick" because it dampens the feedback coming through the frame so I don't have to replace my fillings every 10,000 miles. I don't know if I've explained myself well enough, but like I say, it's all about interpretation.


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## Horze (Mar 12, 2013)

I should further add, it's not the flex you are seeing in CF frames which gives it a smooth ride. But it is in fact the vibration dampening properties of the Compsoite itself. The tiny CF is not what's flexing but it is the lack of road transmission you are seeing (ie, resistance to vibrational conductivity in the material).

@mambo:

These are elementary definitions.

Handling is Handling.
Power Transfer is Power Transfer.
Resposiveness is Responsiveness.

All are distinct. I don't believe there is any ambiguity here. 

Modern frames are stiff enough that it's almost impossible for the rider rider to quantifiably detect flex. It's really a non-issue. As I said power transfer due to flex in the frame is not the issue here. We are referring to responsiveness or also called Reactivity. Modern frames are arguably stiff enough that there is minimal loss of power in the system for the rider to detect.

Again, frame shaping only helps to determine how much frame stiffness you can have whilst altering the weight. Shaping helps control the stiffness to weight ratio. You might make a frame stiffer and/or lighter by shaping it but it won't affect the responsiveness.

The responsiveness of any alloy frame would be the same as that from alloy frames of another generation. If it's alloy the responsiveness is pretty much the same but if it's CF or Composite the responsiveness isn't the same.

Klein Quantum Pro is/was nowhere near benchmark alloy stiffness. Vintage frame from that era is the CAAD5 which is way stiffer in both the BB and Headtube compared to any Kleins ever produced. Klein produced a work of art no doubt but that was about it.


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## mambo (Jul 29, 2012)

I was clearly referring to how riders define responsiveness, not the literal definitions.

The way you define responsiveness in your earlier post is as something very subjective yet this comment of yours suggests that it is related to power transfer - "how quickly it moves OR gives "the perception" of movement when you apply some impulse" - to me that is akin to power transfer, which in your last post you claim is completely independent of responsiveness?? I don't understand how a lighter/heavier frame or that different shaped tubes don't affect responsiveness. i'm sorry but that doesn't make sense. Building a carbon frame is like cooking a recipe up. You put ingredients in (various carbon moduli), you then decide the quantity ( carbon wall thicknesses etc) and the epoxies. The ingredients and quantities in your recipe determine stiffness, compliance weight and responsiveness. You then add the seasoning with the chosen geometry.


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## Horze (Mar 12, 2013)

There's no question about your culinary faculties. The analogy is a good one.

Listen, even the most flexy alloy or carbon frame is going to have a decent amount of power transfer. Things are subjective only so far as having a unitary frame of reference. If you compare alloy to carbon as we're doing here you then have two points for comparison.


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