Carbon Bikes - The Truth. Stiffness, weight & Laminate theory  

Great video, and very, very well explained. As you know, the parameter set involved in carbon design is immense - material choice, pre-preg strength/stiffness, laminate schedule, not to mention fiber draping/drop off etc. Then add loading direction and type (static, dynamic, impact), rider mass, power etc, and it gets even more complex. We’re doing a LOT of FEA-based optimisation in this area, which saves a huge amount of time for downstream production. Here’s a very basic overview, but might be interesting to your viewers. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-C8D8KcBWysY.html

Hello, I found your presentation quite interesting. I make things with carbon every day and don't disagree hugely with what you are saying but there are points I think could be added. I am not adding these things so much for you because you have a handle on the material but for other people reading these comments who might be interested. In terms of carbon fibre, apart from 'The fast and the Furious' franchise, cycling is the home for the most b*ll-Sh*t on this material... you are not wrong there. The first thing to say is that you can certainly wet out unidirectional fibre fully with less than 40% of the entire construction being resin. If you draw a square and put a circle in it that touches the edges you can see the left over space isn't 'nearly half'. 60:40 fibre:resin is just a very reliable resin content and helps carbon fibre, with amongst other things, the ability to deal with shock better. You can certainly buy prepreg prepared with much less than 40% resin. To create 'typical laminate figures' that can be compared, most manufacturers just quote 60:40. Secondly fibres work in compression and tension, although oddly in carbon fibre this figure isn't the same but it does mean that you don't need to have twice as many laminates to deal with + and - 45 degrees because a single spiral fibre (or multiples) deal with torsion in both directions (nearly), so when you were talking about your schedule and wondering if more 0 axis fibres would mean less torsional strength, the answer is obviously yes but it all depends if you have fully calculated your loads and that gets me onto the biggest point. The killer for carbon fibre is its anisotropy and its something I almost commented on in your analysis of Alex Thompson's IMOCA repair. As you rightly state the load path dictates a fibre's tensile strength and modulus. Its very low at 90 degrees and 100% (diluted) at 0 degrees. Now you would think that at 45 degrees it would be half way on the strength and modulus but it's actually way less. For most fibres the modulus and strength is about half at just 12.5 degrees. This means that getting the fibres lined up with the load paths is essential and unlike aluminium which will deal with minor loads without much consideration, if you don't put the fibres into the structure at the correct angles, these minor loads can actually result in failure of the component. That's without going into the use of knits and woven fabrics rather than unidirectional fibres... or the weight of the fabric/ number of laminates... which will all have a bearing on the mechanical characteristic of the finished laminate. The more you want carbon fibre to be strong and stiff in all directions, (like aluminium) the less carbon fibre is amazing. The more you want it to just be strong in one direction the better it is than something like aluminium. In fact I have made and tested structures in carbon dealing with simple loads that are 7 x stronger by weight than a heat treated 7000 series aluminium. That's like super-amazingly-awesome The thing to note there though is 'simple loads'. If you need isotropy, carbon fibre is less appealing because to create a pseudo-isotropic laminate you need to lay fibres in 5 directions and even then its not as strong 'through' the materials as a true isotropic material like metal. Moreover all carbon fibre is not equal. T700 is an OK fibre; I have about 3 tons of it right now and like it :) but there are certainly fibres I use that are way stiffer and also fibres that are way stronger (or both like T1000 for example). Having said that there are also cheaper 'high strength fibres' which have less stiffness and strength than T700 too. With carbon fibre bikes you really don't know what you are getting half the time. Its about as descriptive as asking someone what a guitar is made of and them telling you 'Wood'. One of my big miffs on bikes is that fibres are often blended in that you can add a percentage of ultra high modulus (the stiffest fibres) or Intermediate modulus (the strongest) fibres and the manufacturers label it as being made of that fibre even though most of the frame is made from a cheap high strength fibre, which is less stiff than an intermediate or high modulus fibre and less strong than an intermediate modulus fibre. Sometimes they do something like put 100% T700, or perhaps a higher performing fibre on the backstays (like literally written on the backstays) ... but its only the backstays themselves that are made of T700 or whatever. It would be like selling something as a cashmere pullover when its just got 2% cashmere and the rest is polyester. Some carbon fibre like Zoltec Pannex 33 only costs about £6/ Kg but some more exotic UHM or intermediate modulus fibres are £hundreds/kg as tow on a spool... not oven woven or bonded. There is a reason for that. What I am saying here is that with carbon fibre stuff often the fibre orientation isn't optimised and often the parts are not made entirely from the fibre quoted. You can certainly get very poor carbon fibre structures and consumer carbon fibre bikes are made to a price. This can mean the margins between aluminium bikes and carbon bikes might not be as great as they could be. It should also be noted that aluminium is a pretty trick material in itself, its just that we are so used to it we aren't very impressed with it anymore. If you want something that is tough and isotropic it has a lot going for it. By your own demonstration though you have shown that for a similar strength and stiffness with T700, you have made a tube that is nearly half the weight of aluminium (due to the difference in density; remember the resin is less dense than the carbon) and lets face it density matters. If you look at a steel tube and an aluminium tube, the thing that makes an aluminium tube potentially stiffer is the fact it has a lower density than steel. You can make a larger diameter tube for the same weight because the wall thickness is the limiting factor. If you go too thin on the wall it can just collapse. If you have a bigger diameter tube it is moving more material away from the centre of deflection, which in turn makes a very stiff tube indeed (the reason why a ruler is floppy if you bend it on its side but stiff bending on edge). Due to the lower density of carbon fibre, you could make an even bigger tube for the same weight than aluminium and really rattle your teeth out. The thing is, for some years they have been able to make aluminium frames that are arguably too stiff anyway, so just saying you can make a lighter frame using carbon properly is probably enough, and certainly enough for the weight-weeny website. There is a reason why some people still prefer a custom steel bike or a bamboo frame and its not because they are chasing stiffness. In all honestly all of the above is a bit academic. If you want to make bike components and sell them they have to pass some kind of certification. Governments regulate stuff to stop bicycles randomly snapping in half and unless you crash bikes or abuse them, they rarely do. This is one of the things that makes me laugh my socks off when I read the weight weenie website. If you get into the business of getting CE certification for a bike frame it is put into a machine that wiggles it around tens of thousands of times. The forces applied are calculated and set by the standards authorities. I am pretty sure the calculations they did for the frame we tested were calculated getting a sumo wrestler to bunny hop off the top of a slide or something. The specifications meant the structure had to be way stronger than it needed to be to do its job... in order that it could be sold in the EU. Bikes ridden in competition need to be available to buy and therefore need to pass these same certifications. There is a specification and test schedule for every component on a bike, each being over-specified. If you were being a real weight weenie, it would be designed with the power output and weight of the rider in mind and if a fatter or stronger person got on it they would break it. If you want to really make light bike parts you need to design and make them yourself. You might find that like Alex Thompson's IMOCA, it might break once in a while but if something is close to being a competitive weight, that's sort of what you are looking for. The reality is though the whole cycling industry is a scam, peddling huge wads of BS. You get reviewers coming out with phrases like "they have tightened up the head geometry by half a degree and its totally transformed it" when people like Mike Burrows seems to think a few degrees isn't even detectable without instrumentation. Its an industry that wants to you to constantly buy the latest thing. A bike with round wheels that rolls well certainly helps but being fit will always make you go faster than having a frame that's a kilo heavier, let alone a few grams. Aluminium frames can certainly be made too stiff, so with carbon fibre, all you can really achieve is something painfully stiffer or something a bit lighter. At an elite level it probably makes a difference but for 99% of riders it probably won't. You certainly don't need a carbon frame to commute to work. If you want to reduce weight by a kilo... take a sh*t and save yourself a grand trying to whittle it off the frame. Consumer bikes aside, carbon fibre is a totally brilliant material and the more exotic fibres I use never cease to amaze me. If you want to be impressed with it as a material look up the foiling IMOCA boats and watch them in full flight. Their hulls are made by bonding a skin of carbon fibre either side of a core material, in this case para-armid honeycomb. The skins are only about 1mm thick either side of a 25mm core. Seriously, 2mm of carbon fibre in total is holding a structure like that together. How awesome is that?

The goal of the (marketing departments of the) cycling industry for the past 10-15 years has been to confuse consumers with things that are either intangible or that they cannot be expected to comprehend. Aerodynamics, Carbon Layups, The "Feel" of a bike. All purposefully misquoted and construed with the purpose of stopping the average consumer making an objective comparison to non-branded or off-branded products from the far east. (Where the branded products are made anyway.) I applaud the efforts of the 'new wave' of RU-vidrs attempting to wake up the Sheeple.

That's what I like about engineers like you: analyse the properties of the base materials and their applications, having technical knowledge and understand AND being able to explain it to us viewers. This was time well spent from both sides. I thank you for creating and sharing this video & insights.

Great that the #insidecarbonbikes tag is being used. I have seen some fibre volume data on various areas of a frame and it ranged from mid 40's to mid 50's, some of the cut ups that I have done would be even lower than this in some areas. Currently the variability of properties is a concern, it has improved over the last few years compared to the older frames which were really bad. Also consider that little testing is done in terms of production repeat ability, or critical flaw size etc. Having variable quality laminate or voids, wrinkles etc in critical areas significantly changes the model predicted behaviour. Another one of the things that I have seen is that even if they do all the modelling and laminate analysis and even if the part is produced with low void content, often during preparation for painting at the factory they sand through a number of plies at the corners which makes it all meaningless anyway.

I completely relate to this guy being a disgruntled engineer as a Chamical Engineer myself. So many things annoy me about the cycling industry; but I don't have the motivation to create content about the utter sheiße I have come across. I applaud you for taking the time to address these issues comprehensively and share your work with us via RU-vid.

This is one of my favorite bike related videos already

When I first heard of carbon fiber, it was in windsurfing masts, and in that case, the big selling point was the reflex response rate. Basically, when a carbon mast deflected, it would straighten itself twice as fast as an aluminium mast with the same stiffness. I think the key point here was same stiffness, the sail makers were selling aluminuim as well as carbon fiber masts for the same sails, so the carbon masts had to be the exact same stiffness as the aluminium mast, otherwise one of them would be totally incompatible with the sail. But if the carbon mast had the same stiffness as the aluminium mast, it would of course be a lot lighter, which of course meant that stiffness had a lot less weight to accelerate, and thus it would straighten itself faster. Also, those early carbon masts, around 1990, were hilariously unreliable. Sails would lay rigged on the beach, and suddenly the mast would shatter without warning. Today, carbon masts are pretty much bomb proof and can withstand absolutely unbelievable levels of abuse. I'm always kind of fascinated that no other sport seems to talk about reflex response rates (or maybe tennis and badminton does), it seems to be all about weight and stiffness.

Thanks, I really enjoyed watching this. You have a great style of presentation covering the technicalities but still easy to listen to.

** Hambini checklist ** Powerpoint: check Insults and sarcasm: check Engineering knowledge: check Hating mainstream cycling media: check

As an engineer I appreciate the work required to make this vdo Well done :) PS I still riding steel :)

Thank you Peak Torque! I own an 80s vintage Columbus steel frame bike, two carbon bikes, and and three alloy bikes, and your analysis confirms my perceptions of their ride qualities. They are basically all the same size and I have used more or less the same alloy wheels and tires. Alloy bike 1 is the stiffest, but uncomfortable, as it was not a great design, cheap, with no subtlety in design. Alloy bike 2 is a bit less stiff, climbs well, but compliance is not great on rought tarmac. The 3rd alloy bike is a Wilier and it is lovely to ride, with a balance of compliance, and stiffness, and feels like the steel bike, though it is lighter than all the other alloy bikes and not much heavier than my carbon bikes. The Columbus SL tube bike was perfect for me when I was young and 68 kgs and racing crits. It is relatively heavy, even though it is not stiff. Now I am 73 kgs and it feels "soft". My de Rosa Idol carbon bike is by far the best climbing bike as it has a big down tube and BB386 bottom bracket. Yet is also feels comfortable and it corners reliably without much torsion flex. I feel the designers thought about the layup. My Cinelli Estrada is early carbon tech and was sold as a Grand Fondo bike. It's not stiff at all, quite light, compliant, but I would not recommend it as a crit bike. It is much less stiff around the BB than the de Rosa. This confirms your conclusion that there is just too many variables like the size, geometry and weight of the rider, plus the riding style, and as a consumer, there is very little chance to know these details about layup and design. Intelligent and unbiassed test riding and reviewing is needed more than ever.

First of all I would like to thank you for producing this video. I am enjoying your videos for some time, the first one I saw was about mounting a Quarq power meter and a BB - I still remember the comment that if you waited for industry to sort itself, you would never get a power meter :) The generalized marketing message I am reading/getting from the cycling industry related to the carbon material is: 1. Carbon is lighter 2. Carbon's stiffness can be controlled and "strategically" used in different areas of the frame differently unlike Alu 3. Pros ride carbon so it's stiff / stiff enough 4. Price is high 5. Carbon product is premium 6. Premium manufacturers have knowledge, engineering experience, CFD, "win tunnels", etc. so they know how to "properly" make a CF product unlike "far east". None of those points seem to be denied by this video. Which is probably good - I wasn't a complete fool. Keep up the good work!

Very interesting topic I would have never otherwise been aware of. Thank you for spreading the knowledge.

Thanks for the information, clear and well presented. Keep up the good work!

Great video and very insightful! Completely forgot about the impact of the epoxy to the overall modulus of that carbon/layup modulus.

Such a GOOD VID, been binge watching some of your vids and they are all very technical which is amazing! Good work

As a fellow Mechanical Engineer, I highly enjoy these analysis videos you make. Cheers.

Why have I only found your channel now - very informative thank you and take a bow

Found you through Hambini. Glad I did. You're both debunking marketing shite. Love hearing engineers giving us a proper insight. Many, many thanks. Subbed.

I tell you mate, you have made the most interesting technical video I have ever seen. You really have great knowledge, and more importantly, communication skills. Fair play to you. I respect you. Thank you.

Too funny. Just sent this video to friends for their viewing, As it turns out, one of them happens to ride with you in HK. Anyway, great video

Matrix algebra took me back to engineering school, a few decades ago. Thanks for all the work that you put into this video!

Well explained👏. Owner of 5 carbon bikes... but always felt my CAAX does not really stands back... makes more sense now. Thx for a great video.

Great and very informative video, thank you for putting this together. The bike industry is full of so much hype and they play it up to the insecure audience which swallow it up. Most of the cycling channels on RU-vid market questionable products to an audience which doesn't understand how things work and worry more about looking stupid, out of fashion or falling behind on what their friends have purchased or adopted. In addition to this engineering approach we may need a cycling psychologist channel where they promote self confidence and being content in their own skin.

great video!! I think Giant does some of the best carbon layup

Late to this party, but this time last year decided to bin the cheap carbon for an Emonda alr5 which I was amazed at once built how light it was for the money. Appreciate the video and time spent putting it together. I’m all for Aluminium Frames, so much lighter... on your pocket😊👍

What a great video. Loved the info about how to calculate the carbon layers, not something easy to find!

Thank you very much for the video. It's the clearest explanation I've seen of exploding the myths of carbon fibre material stiffness that I have seen. Just a couple of points though: It might be worthwhile mentioning fibre wrinkling as a major contributor to lowering the specific stiffness of the material. Not only inadvertently wrinkling but also that due to woven fibres. Or maybe that all just complicate things too much the viewers. Secondly, Michael Ashby's book Engineering Materials 2, chapter 25, Table 25.2, has some useful data on specific strength and moduli composites vs aluminium alloy. Thirdly it might be worthwhile clarifying that you're talking about material stiffness only. A follow-up video on the influence of (tube) geometry might be a useful contribution. Finally it would be great to see your communication skills put to addressing the 'stiff yet compliment' myth. Terry

Great video. It’s like sitting in Prof Ian Farrows lectures again! Haha

Great content, thanks for the clear explanation! I have a question, though: how do RTM carbon frames (like the Time frame covered by Hambini's video, for example) compare to laminate CF ones and Al? Keep the excellent work, =)

Thanks , you answered a lot of my questions

Good explanation of the issues relating to sizing and analysis of carbon laminates. Brings back happy/frustrating memories stressing laminates on Airbus & Military aircraft. Retired now & I think I miss the technical stuff (but not the timescales!). A little bit jealous:)

Outstanding explanation thanks much appreciated. Things everyone who owns or is contemplating a carbon frame ought to know 👍

Great video! Better than some of my undergrad lectures (from what I can remember of them). Another thing that would be interesting to talk about would be toughness & material degradation mechanisms (carbon fibre vs aluminium). I don't expect I'll be riding the same carbon fibre frames in 15 years time (for a variety of reasons), whereas I'd expect my aluminium commuter to still be going strong!

❤️ at last I found someone who knows what they are talking about!

Great video! Also worth notice that CFRP laminates experience coupling between bending-twisting, compression-bending etc. depending on layup, which is described by matrix A,B and D in Classical Lamination Theory (wing of Northrop Grumman X-29 is really interesting example). In terms of bicycle frame rigidity this can be an advantage and disadvantage. Regards

Incredible well done. Best explanation I have heard about carbon fiber. Well done. Thanks

I hope you enjoy this. It took an aeon to make :) For the record and being correct:- @ 6:30 I mean flexural modulus not tensile @ 8:40 I mean flexural modulus not tensile @ 13:08 I mean modulus not stiffness @ 15:44 I mean flexural not tensile

Interesting! I have had and used nearly daily a Specialized Roubaix SL3 carbon fiber bike frame for almost 10 years, well over 35000 miles, and its what I consider bombproof. I'm also a heavy rider 239lbs.

I've gone for aluminium bars and extensions on my Time Trial bike for three reasons: much cheaper, and actually less than 100g difference (about 3 oz in imperial) and I've seen a few clips of carbon bars failing on TT bikes in ways that I've never seen with aluminium (bearing in mind that I'm an amateur on a budget I was concerned that any budget bars I bought would be even more likely to fail than the professionals' bars). Watching this seems to confirm that I made a good choice (beat my PB this year too, not bad at 62!). Thanks Peak Torque, I love your technical analyses.

Excellent video as are his other videos very very informativ eand helpful.

Love your informed videos!!!

tom ritchey said in a inteview, that only think why the manufactures moved from steel to aluminium in 90's is, the aluminium frames have space for a bigger brand decal.

I think the Industry does know they cant get it right, thus keep changing the shape to "marketing obsolete" the previous build and keep repeating this process, and maybe add another gear, etc... . Great Video - Thank You !!

Amazing video, thank you 👍👌

This is amazing, thanks so much! As a sailor who has done lots of research into dyneema and other synthetic fibers, it seems they fall into a similar situation. Lots of nonsensical marketing wank and total bs to confuse the consumer. Drives me up a wall

Plus for all the uncertainty/ball ache in manufacturing and QC let me refer you to messrs Luescher and Hambini!

For me the bigest advantage of CF is that your Can tweek the shape of the frame more easily to put material where strenght is needed. That's how, Compared to hydroformed aluminium tube frame, you get lighter and stiffer bike. And an other important advantage of CF compare to AL is fatigue strenght.

Thanks for your upload and lesson. I think the "only" brand which creates a very good compromise between stiffness and lightweight is still spin-system bikes from Germany in Kassel. But for sure in the end its is also a question of how popular a material is.

Great content. Keep it up!

Thanks for that. I've always thought the ability to vary, and control for, stiffness in some directions and compliance in others was the main feature, aside from weight, of CF versus AL (which makes it possible to build a more comfortable bike, seat post, handlebar, etc.). If I understood the presentation correctly, it sounds like that's something engineers could intentionally do as part of the layup (assuming the knew what they were doing). Do you think OEMs actually do that, or that is more likely to be a bug sold as a feature?

Impressive video! Just subscribed!

I liked it :). Could you comment on which aluminium frames seem have optimised where to put the mass? Or do you think the idea of putting more carbon mass where it's needed wins? Weighing 100kg I'd happily have a bike weigh an extra kg and cost £1000 less. Maybe aluminium manufacturers trying to go super light have actually screwed themselves. Can you discuss longevity of a mid range aluminium frame vs say a basic Giant TCR or Canyon Ultimate?

This is explained very well, as long as the listener understands the principles in terminology, shear, tensile, tortional etc. Explanation of the downtube forces was great, see Trek with straight shot down tubes with a large box sections. A lot of the problem is aesthetics & aerodynamics Vs structural integrity

brilliant video and well explained, i am a chef and thick as .... academiclly :) but even i understood it..... what is youre take on Moots bike frames ? do think they would be worth it or just another cycling industry gimmick ?

Nice Video. Another fun fact is that each fiber not only the bundle must have epoxy on it. You can not have dry fiber touching dry fiber. The polymer mechanics are very impressive also.

Really nice technical video. The part I find most amusing about the whole bike frame game is that people massively overrate how frame properties actually affect riding a bike from either a comfort or performance standpoint (aerodynamics excepted). It's all angels dancing on the head of a pin.

Thanks for this video, I was very to the point and objective. It actually reflects my personal experience switching between aluminium and carbon bikes: carbon is for sure lighter but not necessarily stiffer. The stiffest (impression) frame I have ridden is the aluminium Colnago World Cup cyclocross, specially the way that bike deals with potholes is amazing, it just takes the impact without any flex/vibration. I also had a Specialized Venge which felt very stiff torsionally (pushing hard out of the saddle) but which was also having a lot of road vibrations in the frame and so was very uncomfortable to ride, eventually after just 3k km and a few rides in the rain the BB started creaking so I sold it. Now I don't want carbon bikes anymore, they are lighter but a lot more expensive and not durable (creaking issues) versus the aluminium equivalent. Could you also make a comparison of alu vs steel. I also think steel is also overrated versus aluminium. Steel is more expensive, heavier and I do not believe anything about the statements that it is more comfortable due to better at absorbing vibrations. I think that if it a steel frame is more comfortable it is due to the frame build but not due to the material. I find it sad they don't make any high-end aluminium bikes anymore, I still think it is, everything considered, the best material to make bikes.

Why are the joint sections in aluminium frames not mentioned? I think they have effects on the stiffness of an aluminium vs a carbon monocoque frame!

Which current climbing frames is the stiffest ? I feel the width of BB plays a part too..ie Bb86 vs BB30, former being stiffer

Awesome video !! Carbon still is a wonder material, maybe not for the stiffness but being able to makes bikes lighter has help out a lot and being able to shape the tubes and every other area of the bikes has and is a real good thing for bikes !! And it looks really cool even if it isn't painted. No material is perfect. But, the best engineers in the World seem to use it in all high end industries, from bikes, cars, planes, helicopters, space, and it has realky changed and improved many things in many things. So, it is actually a big improvement and in a real way a wonder material.

I do enjoy your videos. Aluminium does have diectional stiffness, particularly for extruded and rolled aluminium, which is why aircraft components have to be machined in sympathy with the grain flow of the aluminium.

Chugging through your back catalogue ~ great video ~ never ridden a carbon bike and not sure I like the engineering of carbon due to the way it fails ie snaps when you need it ~ so this was interesting

Nice technical video. What about cost of maintenance and durability differences if any?

As a fellow mechanical engineer, perhaps the best video I have seen comparing carbon fiber to aluminum bicycle mechanical properties.

I'm a mechanical engineer myself, but never dealt with composites and carbon fiber. Nevertheless...having the background knowledge to understand what you are talking about I must give you massive kudos for the clarity of your explanation! Furthermore I'm also a very keen cyclist! I have an OPEN U.P., which is considered as an excellent bike by basically anyone. And in fact, it is! But for a very long trip that I'm planning for the summer (now with Corona we will see if I manage...shit virus...) I got a Mason Bokeh. This was driven by the fact that I wanted something a bit more stable than the OPEN and on which I could pack more luggage. The bikes have very similar tires (WTB Horizon on the OPEN and WTB bywayon the Bokeh, both 650b), the OPEN has carbon rims and the Bokeh has Alu rims, but they are both HUNT and they are almost the same in geometry (the rims I mean). I tend to ride the Bokeh with much more load on it, but when I ride it only with bottle and spares I actually don't feel that much difference with respect to the OPEN. The handling is a little bit slowlier because of the geometry (longer trail, longer chainstays...) but when I stand up on the pedals and put down some power I feel basically the same stiffness from the frame. I'm not advertising Mason bikes here but you would not believe how good that bike feels and handles for an aluminium frame. And, added bonus...threaded BB!! True it's heavier...but hey, that is supposed to be carrying 15Kg of luggage so a few hundred grams more on the frame will be negligible! All of this digression just to tell you that from my epxerience I agree with what you said! And that I loved the video!

@Peak Torque... Can you go through the process of designing a carbon seat post? I think it will be instructive for everyone as it involves Euler's Column Formula.

Hi, Interesting video, thanks for sharing! Just wanted to ask one thing about the calculation of stiffness: I was wondering whether it was correct to calculate with the angles deviating from 0 degrees. I guess those fibres were placed on that angle because there are forces in that direction as well, right? So to those forces, the angle would actually be 0 degrees (and thus the stiffness would be high). For example: at the BB, there are forces perpendicular to the frame. Fibres in that direction contribute to the overall stiffness, I assume. Put differently: measuring stiffness in just one direction might not cover 'overall stiffness'..? Anyway, these are just some thoughts from a relative layman, I am sure you have considered this. Best, Thomas

Great video. This helps me not fall for the marketing hype. It's hard to justify spending 50-100% more for the relatively small performance gain. I'll accept the penalty of a few watts of performance and use that money for a professional bike fit, better tires, kit, and perhaps an upgrade of my tools that will keep my bike operating efficiently.

Super interesting!

Thanks for the insights ! Riding carbon bikes feels a bit like riding a kite ( kind of scary ) . Titanium / alloy parts on a Columbus Genius or Max build is the peak of cycling technology for me . GS

Question: Cannondale offer normal carbon fibre frames and then hi modulus versions... What's the difference, am I right in saying the hi mod will just be stiffer as it's not that much lighter, only around 200/300 grams

Thanks for the video. Very eye opening! I'm curious how this information applies to smaller companies like Tsubasa whom manufacture their own custom carbon tubes etc.

Great video debunking the bs that is feed to us by the cycling industry. I’m guessing that some of the key IP that a large cycling brand has is the load cases for its various products, road, xc, dh etc. That it has catalogue over time via instrumentation of bikes in use that is continuously refined. At least I hope so! If it’s anything like the industry I work in there probably is a peculiar load case that’s not normal to everyday use that generally bulks up the laminates. I could just a top tube sitter, the Danny Mac wannabe or the who put that fooking curb there load cases really changing things from the day to day use.

Very interesting, thanks you very much ! :) So do you think a high-end aluminum frame would be a better investment than a entry level carbon frame ? :)

Great video!

Well explained mate. I'm Chief Eng in an aerospace business and do deal with laminates quite a bid. You did stumble over your properties a couple of times but still great job of dis-disillusioning people of this marketing magic. Also worth mentioning is that the quality of the end product does not only depend on design quality (which you described and is quite difficult) but even more on the quality of the manufacturing process which I always liken to baking. Minor changes in the process can significantly affect the outcome and we rely on people to get it right... AndyB

So, are the 7-800 gram carbon frames now available not stiff enough?

I do a few vids like this, and most people just won't believe it, it is amazing how good the marketing is surrounding bikes. People just argue blindly and give examples of tests carried out on GCN, cycling weekly, etc. Which we know are not proper tests, by an independent body. It does amaze me how people really swallow the kool aid. All i can say is marketing is more powerful than the truth.

Great vid. What about the possibilities that carbon offers towards the fabrication of more complex tube shape? Doesn't this give an extra advantage with respect to torsional and bending stifness?

Nice explanation. It's so easy to make mistakes during layup and production too since carbon fiber is so labor intensive. True, they are using laser cutting and robotic assembly now on some of the more advanced production floors, but unless you're a sponsored racer and you need lightness to win, is it really worth the expense? I'd focus on getting in better/leaner shape before running out and spending bank for a status symbol, unless that's your thing, which isn't doing the bike's function any justice.

Curious to learn your thoughts on integrated carbon stem/handlebar?

I do enjoy your analysis. The engineering of a laminate is quite complex and that does not take into account the variations in manufacturing. Your work up emphasizes why the young modulus of the material is far more important. Frankly I will will stick with steel.

this is amazing

Really interesting video. There are very few people that know what they are on about and are willing to tell people why bike manufacturers and marketing companies are chatting out of their arse

After watching Luescher Teknik's videos I doubt many carbon frames' layups actually conform to original design/requirements. You might design the ideal layup but manufacturing will wreck that. There appears to be very poor QC in the industry.

Fun fact: in 2012 I ordered parts for a dream bike. I had a cheap aluminium bike with shimano 105 + Mavic Aksium wheels. I ordered Ultegra, a Ridley Damocles frame, a good saddle and Mavic Cosmic Carbon wheelset. The Mavic wheels got heavily delayed so I built up the bike with help from a bike mechanic, then since I couldnt wait I smacked my old Aksium wheels on the bike.- I literally couldnt feel any difference at all. Zero. Thought it was the same bike. Then a month later I got the Cosmic wheels and OH MAN! what an upgrade. The bike became SUPER responsive! If I had known all I needed to buy was a new wheelset that would be the only thing I would buy. So yeah, carobon fiber hype.

what about the "comfort and compliance" where it's needed vs stiffness where that's needed claims they love talking about? can you engineer that in an alloy frame?

Great video. I really mean it.

I'd love to see you do this analysis on rims, carbon vs aluminum. It should be the same story. People say that the carbon rim is stiffer. But the same cross sectional shape should be about the same stiffness. The deflection of tire and tube should be orders of magnitude higher than that of the rim. My theory is that people change wheels and maybe throw on new tires and they pump them up hard, go for a ride and it all feels stiffer and what they really feel is freshly pumped up tires.

Finally a video on actual composite engineering! Having studied composites it's so frustrating hearing people all of the time treating CFRP as "black aluminium". Really enjoyed your analysis, based on UD laminae, but i'm afraid most manufacturers incorporate alot of woven layers in areas like the bottom bracket and headtube just to get rid off of all the hassle and make the manufacturing a bit easier. Ride on mate!

How's does the tube's geometry (shape) play a factor? Round tube versus aerofoil? Can shapes that are more easily achieved in carbon moulds versus hydroforming make a difference? If there's any difference at all? For your 50mm round down tube example, can you speculate weight difference? Complex aerodynamic hydroforming still seems limited in aluminium bikes, though that might be because the business decisions around justifying the hydroforming jigs cost on a frame that the brand's know can't sell for as much. But that's because consumers are brainwashed into aluminium being a "cheap" material. Finally, the majority of aluminium frames I've seen are 6000 series aluminium, not 7000. What difference, if any, does this make? Great video as always mate 👍🏼

The tensile stiffness is only one part. There are compressive components to the stresses on a bicycle frame. The seat stays and seat tube for instance. I would surmise that CF has only the compressive strength of the Epoxy resin. Depending on which particular resin starts at 69MPa . 6061 Aluminum is around 207 MPa.

I like this guy..... understands the truth about CF, which isn't that diffcult to understand. When I repaired the bumper tabs on my car, I could have used glass fibre or similar but I used CF because it's easier to work with. It isn't some magic ingredient. I prefer an aluminium bike frame as it's far more durable and far cheaper!

Would be interested to hear your opinion about steel and titanium as well. There is a lot of BS thrown around in this part of the industry as well ("ride quality", "road feel", "forever bike").

If you were to design a bike what would it look like?

This is so good!

Great stuff! I'm from the sailing world, although my mountain bike has done several thousand miles, and I am forever trying to tell sailors that carbon isnt the holy grail material. In fact a carbon bow fitting to replace a stainless steel component ended up weight 80grms more but cost £800! Not forgetting the fiting of the item, which needed hull surgery and, therefore, more cost. So to replace this metal fitting ended up gaining weight and cost over £1200 fpr the privilage of having carbon.

You know...I would like to see other patterns used! Kevlar ect... but there is also a hexagon pattern called dragon skin carbon! They even have carbon and kevlar intertwine fabric. But the best thing would be to have a better epoxy or a hybrid epoxy! Graphene is good additive. But ultimately aluminum is dope! Andrew Low of low bikes in San Francisco is probably the best hand made aluminum bike maker! Double pass welds. Huge head tube. Down tube is extremely large. Just Gnarly!