The Fat Cyclist Explains: Carbon Fiber

07.28.2010 | 6:32 am

A Note from Fatty: I’m pleased to announce a new series, wherein I explain difficult cycling techniques and technologies in clear, simple English. Except for when it makes better sense for me to explain in French, in which case I will of course explain in English anyways, because I don’t know French.

If you have a cycling-related question you would like explained, simply email me. Due to the volume of email I receive, however, I cannot respond to all questions individually. In fact, I to hardly any of it.

OK, the truth is I haven’t checked that email address in months. But I will soon. I promise.

And now, on with the explainification!

What is Carbon Fiber and How Does It Work?

I recently received an email which I had slightly less-recently sent to myself. This email went as follows:

Hi Fatty,

First, let me begin by saying that I’m a big fan of your blog. I don’t know how you come up with your insightful, witty, and down-to-earth cycling commentary on a near-daily basis. The only person I’m aware of who writes more about cycling than you is Lennard Zinn. Oh, and Bike Snob NYC writes more than you, too. So that’s two people who write more cycling-related stuff than you. And they’re both better than you, too. No offense.

Anyway, the reason I thought I’d email you is to ask a question that’s been bugging me lately. It seems that more and more biking stuff is made from carbon fiber. Frames, cranks, handlebars, seat posts, brake levers, stems, bottle cages. Practically everything.

I understand why they’re doing this: carbon fiber is light, it’s strong, and it can be made into practically any shape. Fine, I get that.

But what the heck is carbon fiber? I mean, I know what the two words are, kind of. “Carbon” is what pretty much everything in the universe is made of, and “fiber” is a thread of some sort or another, and if you eat enough of it, you poop on a regular basis. Excellent.

But when you put those two words together — “carbon fiber” — somehow you’ve suddenly got this outrageously strong stuff that’s really light that you can make into any shape?

It sounds like dark magick to me, Fatty.

Please help me understand what this stuff is and how it works, so I can explain it to other people without giving you credit.

Best Regards,


PS: Please also explain how CDs work.

Duane, you’ve asked an interesting question, and a timely one at that, since I am currently in the process of revising the Wikipedia entry on carbon fiber for accuracy and completeness. And also, quite frankly, for interestingness, because the current entry is so dull that I simply have not been able to bring myself to read it.

Here, in plain and understandable English, is my explanation of what carbon fiber is, how it can be shaped into practically anything, and why it is is so light and strong.

What is Carbon Fiber?

Carbon is the most plentiful element on Earth. Except hydrogen, I think. And oxygen too, maybe. And probably nitrogen, or was it helium? But after that, carbon for sure.

My point is that there’s a lot of carbon.

But what does carbon look like? Well, coal is pretty much pure carbon. So there you go. Carbon is black and flaky, and it’s pretty heavy. And if you drop it it shatters into a bunch of pieces.

“But Fatty,” I hear you say, “Heavy and rock-shaped and flaky and brittle aren’t the kind of properties I generally associate with carbon fiber bikes at all! Or at least not for the past couple years!”

And that’s because carbon is only like that (heavy, brittle, and coal-colored) before you turn it into fibers. Now a “fiber,” as you know, is really nothing more than a thread. And threads are flexible (not brittle) and light (not heavy) and don’t shatter when you drop them on the sidewalk.

So you definitely want to make your carbon fiber-y if you’re going to make a bike out of it.

To do this, you extrude coal through something that’s kind of like a pasta maker, except the pasta is really, really thin. And it’s not extruding a semolina-based dough, it’s using carbon.

And then, once you’ve put the coal through the pasta machine, you boil it for eight minutes. Any longer than that and you’ve got soggy, limp carbon fiber and no amount of pasta sauce and cheese will ever fix it. Believe me, I’ve tried.

[NOTE: Since coal is 99% pure carbon, and coal burns, and most threads burn, be aware that your carbon fiber bike is very, very flammable! And it will give off a thick black smoke when it burns, and the EPA will come and have a very stern conversation with you. Still, the knowledge that your bike burns can be useful in survival situations. But if someone dares you to jump your carbon fiber bike over a bonfire, do NOT take the dare.]

Why Is Carbon Fiber Light?

Now that you understand what carbon fiber is, your next question is, undoubtedly, “Why is it (i.e., carbon fiber, not your question) light?” The answer to this (i.e., carbon fiber, not your question) is really quite simple. Carbon fiber is light because a fiber is nothing more than a thread, and threads are light.

Here’s a way to prove this to yourself and friends.

First, pick up a thread, maybe a foot or so long. See how light it is? Put the thread on your bathroom scale. On most scales, it doesn’t even register. Pretty amazing, if you ask me.

Now, just for fun, put another thread of about the same length on the scale. See? Still doesn’t register, does it? You know why? Because fibers have no weight. Mysterious, I know, but demonstrably true.

The real question is: since fibers are weightless, how come carbon fiber bikes weigh anything at all? My personal theory is that bike manufacturing companies put ball bearings in the downtubes to add weight, putting in slightly fewer ball bearings each model year. This allows them to claim less and less weight (and hence a reason to upgrade) every year.

It’s a lousy trick.

Bicycle manufacturers of the world, I’m putting you on notice. Stop putting ball bearings in the down tubes and give us our weightless bikes now!

Why is Carbon Fiber Strong?

As you know, carbon is the primary element in diamonds, and diamonds are unbelievably strong. Here, try this. Look around you and pick up a handy diamond — the biggest one you can see. Now, try to bend it.

You can’t, can you?

Now, place it between your palms and try to crush it, like you would an orange.

Not easy, is it?

See how strong diamonds are? That’s why carbon fiber bikes are strong.

But there’s even more to why carbon fiber bikes are strong. In fact, the strength of your carbon fiber comes from a number of different factors:

  1. The weave of the carbon fibers. Three-strand braids are extremely strong, but are rarely used. The reason why is quite interesting. Long ago braids were almost exclusively used in factories, but since most guys cannot braid to save their lives, most of the carbon fiber braids were executed by women. A discrimination lawsuit was brought to bear by a man that felt put upon, and that was that. Now the basket pattern is used most often, although some people are working on a new “interlocking pretzel” pattern, which sounds both promising and delicious.
  2. The thickness of the carbon fibers. Thicker is of course stronger, and the best carbon fiber bike would be where each tube is one really thick fiber. But science doesn’t know how to do that yet, and I haven’t told them because they haven’t offered me enough money.
  3. The kind of glue they use to hold the fibers in place. Most manufacturers go with a kind of epoxy, which is fine. Be aware, however, that some of the cheaper manufacturers use straight-up Elmer’s school glue. The best way to tell if your carbon fiber bike is mixed with Elmer’s is to smell it. If it smells like Elmer’s, it probably is. The BEST kind of glue to use, of course, is Super Glue, because that stuff is strong. But hardly anyone ever uses this anymore — even though it’s incredibly strong — due to the fact that factory workers kept gluing their fingers together.

How Is Carbon Fiber Shaped?

The final aspect I’ll cover is how carbon fiber can be formed into practically any shape. Well, first the manufacturing plant mixes some glue up and then they slather it over a layer of the carbon fiber weave, and then they do that same thing again and again — sort of a glue-and-carbon-fiber lasagna — and somehow make it into the shape they want it to be.

Or something like that.

Honestly, I have no idea how. Maybe they pinch it into the shape they want just before the glue hardens. Or maybe it’s magic. It’s a total mystery to me.

Anyway, that’s how carbon fiber works. I’m glad I could explain it to you.

PS: CDs work by using lasers!


  1. Comment by Gunther (from Germany) | 07.28.2010 | 6:49 am

    Wow, looks like I’m the first commenter today. A quotation from the film “Shakespeare in love” concerning how they shape carbon fiber into any form: “I don’t know, it’s a miracle !”

  2. Comment by Penina | 07.28.2010 | 6:59 am

    Thank you, Fatty. It is now clear as mud!

  3. Comment by Razor | 07.28.2010 | 7:11 am

    Dear Fatty

    So – if carbon fibre is so closely related to Diamonds, why isn’t Mrs Razor chuffed when I buy us (well me really, but she can ride it if her feet reach the pedals) a carbon-fibre bike, or parts there of???

  4. Comment by DavidV | 07.28.2010 | 7:23 am


    For the next version can you explain why wearing ‘good’ cycling clothing (read expensive) does make you much faster. I just got some Livestrong Jawbones, and when I’m riding along and see a reflection of myself I think two things:

    1) I look like Fatty, but hopefully not 45…
    2) I look really fast, therefore I must be really fast, therefore really these sunglasses were a good investment as speed is expensive and these glasses were cheap when compared to a Porsche.

  5. Comment by Philly Jen | 07.28.2010 | 7:51 am

    Hmmmm, Bike Snob always spells it “crabon fibré” — so I guess this means he knows French?

    I myself am fond of stinky cheese.

  6. Comment by Greg @ Greg Rides Trails | 07.28.2010 | 7:55 am

    If all it is is glue and fiber, I think I have the next break through frame material: GORILLA GLUE CARBON FIBRE! (Patent Pending)

    I’m going to make a mint…

  7. Comment by neil | 07.28.2010 | 8:27 am

    That explains a lot actually. I am a ludwig and don’t pay much attention to things like this, but I thought they were saying “carpet-fiber”.

  8. Comment by bahama mama | 07.28.2010 | 8:43 am

    I now feel confident that I’ll pass the properties of materials portion of the PE exam.

  9. Comment by Stranded | 07.28.2010 | 8:53 am

    If I’m not mistaken, BikeSnob spells it “crabon fribe” (with appropriate acccent mark or marks). Funny stuff–I plugged it on my blog. Thanks!

  10. Comment by zeeeter | 07.28.2010 | 8:53 am

    As you are clearly well read and as nerdy as I think I am, you might want to take a look at this to fully clarify your explanation!

    And it even starts from a bike!

  11. Comment by Steve | 07.28.2010 | 8:55 am

    It’s like reading an episode of Bill Nye the Science Guy.

  12. Comment by Matt Langridge | 07.28.2010 | 9:06 am

    Dear Professor Fatty

    We at The Nearly Top Secret Airplane Manufacturing Co. have been trying to fathom the secrets of Carbon Fibre for decades. I have just referred your article to the monkeys in our R&D department. They made lots of happy hooting noses and then offered me a banana in thanks!

    As a result of your explanation, we can now start to make Top Secret Carbon Fibre Planes of our own and give those guys at Northrop and Lockheed a run for their money.

    I think the Skunk works boffins will be hard pressed to beat us now. They must be quaking in their boots.

    Thanks again.

    Mr Fuzzy.
    The Nearly Top Secret Airplane Manufacturing Co.

  13. Comment by MattC | 07.28.2010 | 9:57 am

    So let me get this straight…Diamonds are made of Carbon….so a carbon fiber bike is really just a big ol’ diamond In the Rough (ITR). Hmmm…I know my wife wants a diamond for our 10th anniv (coming up soon).

    I can do that…and then I will also want a diamond…only mine will be the ITR version…now it’s how to decide on which diamond to get….maybe a Cervelo RS3? Gosh…so many diamonds, so hard to choose! Thanks Fatty! I’m sure my wife will thank you too!

  14. Comment by Yaroslav Popovych | 07.28.2010 | 9:59 am

    carbon fiber good, make bike go fast I think

  15. Comment by skippi | 07.28.2010 | 10:03 am

    Your explanation has so confused this computer that it is no longer working correctly! Perhaps those i met at the Tour and recommended writing in to you and sending anecdotes(dictionary not working either), and photos will help you with your french, some were french who spoke english with a funny accent , others were from USA who spoke english with a funny accent and others knew your blog and laughed in a funny way!

    Rode the TDF with a metal bike because if it broke the welding would not start a bonfire and pollute the atmosphere!

    Georgethecyclist, fatherandson , skippi-cyclist can be googled for your entertainment.

  16. Comment by bikemike | 07.28.2010 | 10:10 am

    If i were to go to the local grocery and buy bags of charcoal, how much and how long would it take to build a nice carbon frame? I really like the new Specialized S-Works Roubaix SL3 but i can’t afford retail prices.

  17. Comment by roan | 07.28.2010 | 10:27 am

    Fatty, my concern about carbon fiber is the flammable characteristic. Since you ride faster than I do at this time but I plan on going faster than you soon…Is there a sort of color indy-cator that lets you know when you are approaching terminal speed flame-out due to wind resistance other than the black smoke? I’m planning on pushing the envelope and would like your in-put on the gravity of the situation.

  18. Comment by SuomiTri | 07.28.2010 | 10:59 am

    Wow. as a sciency kinda guy (but not an engineer), that explanation made me vomit a little in my mouth.

    on an unrelated note, you won’t eat our meat, but you’ll glue with our feet.

  19. Comment by Lisa | 07.28.2010 | 11:07 am

    My boyfriend recently upgraded to a Carbon bike and LOVES LOVES LOVES it. It’s so light! And he’s faster and does better on hills.

  20. Comment by Jack | 07.28.2010 | 11:11 am

    I can contribute something about the speed when you catch on fire. Fatty rides at higher altitude than many of us. Less oxygen means less chance of igniting your frame or other carbon parts. I do not know how much expelling pockets of bodily gas around your bike increases your chance of combustion. Fatty may have more experience in the bodily gas department.

  21. Comment by Marion | 07.28.2010 | 11:47 am

    Dear Sensei
    I am so enlightened now about carbon fiber and bikes that cost more than diamonds.
    Thank you,

  22. Comment by Joe | 07.28.2010 | 12:11 pm

    Carbon fiber’s only awesome until it isn’t – until it catastrophically isn’t.

  23. Comment by thomas bagby | 07.28.2010 | 12:53 pm

    Nice post and explaining briefly what carbon fiber is. I work with carbon fiber on a daily basis at Boeing. I work on the 787 DreamLiner in Everett, Washington. Let me tell you, carbon fiber is extremely strong and can be difficult to work with. It is lighter than aluminum or steel, but has to be handled quite differently also. It is also as strong if not stronger than aluminum or steel as well. I plan to purchase my next road bike made exclusively from carbon fiber. I just need to decide on whether to go Scott or Giant.

  24. Comment by Joel P. | 07.28.2010 | 1:12 pm

    Thanks Fatty I are much smarterer now.

  25. Comment by classyhick | 07.28.2010 | 1:50 pm

    I have 5 pounds of charcoal briquets and a pasta maker set up in the kitchen. The pot of water is almost boiling, so I should have a new bike in 35-42 minutes. How exciting! I’m not an engineer, or a chef, so I was hoping you could offer advice on cooking some matching carbon pasta fiber shoes? My method is to pat the fibers into a hashbrown looking lump, heat in a frying pan, top with running shoes and allow to melt together. Will placing my head in the pan be suitable for making a helmet?

    Please send a pack of FatCyclist stickers so that you get credit when I hit the road!!

  26. Comment by evil3 | 07.28.2010 | 1:53 pm

    I think I am the only one who has gotten a lower IQ after reading this. Not because the fact that about 90% of it is funny false info, but because I can’t stop picturing someone trying to extruded a diamond in to a thread so they can make their own parts.

    Really I know how it is truly made, and how things are formed. But sadly the last bit about how it is formed is very close to how it is really done so in turn that means you gave us false info. lol

  27. Comment by Drew | 07.28.2010 | 3:07 pm

    This was a great post, Fatty. Thanks very much for taking the time to write it.

  28. Comment by rokrider | 07.28.2010 | 5:40 pm

    So, let me see if I’ve got this right. If I eat my bike I’ll poop on a regular basis?
    Frankly I think there’s got to be a better way.

  29. Comment by gomez | 07.28.2010 | 5:46 pm

    Bahama Mama,
    sorry to disappoint you and make you feel put down, but this won’t help your PE exam AT ALL. You see, a Physical Education exam is made up of doing various hard things, none of which (unfortunately) involve riding a bike, like it should. If–and this is a big if–the rope you have to climb is made of carbon fiber, then it will help that part of course, but it won’t do anything for the 40-yard dash, or the situps or pushups.

    Sorry to break it to you.

  30. Comment by Preben | 07.28.2010 | 6:35 pm

    Mate, that is funny as, I could not imagine handing the future wife a bike to wear on her finger though. :)

  31. Comment by Fiona | 07.28.2010 | 7:50 pm

    Maybe you can explain to me why my partner ‘needs’ more than 3 bikes. I haven’t figured out how he can ride more than one at once, but that argument doesn’t seem to wash with him.

    OK – so maybe you’re the last person who can explain this to me.

    But I’ve always wondered!!!

  32. Comment by Phill | 07.28.2010 | 8:20 pm

    Here’s a great little video promoting BMC’s new Impec. If you haven’t seen a carbon weaving machine in action before it’s worth checking out. Swiss precision at it’s best!

  33. Comment by Gordon In Melb, Australia | 07.28.2010 | 8:53 pm

    I wish to comment on the previous post now so mre read it and check. Notice how many comments to the comments Fatty made about his age …. he realli is THAT shallow.

  34. Comment by ac | 07.28.2010 | 8:53 pm

    neil has it right it’s all just “carpet fibre”.
    Or alternatively, congealed soot.

    I think BMW make a novelty bike-like object with all the cool M-series logos and everything which they say has an anthracite frame. (anthracite is a type of coal BTW)
    See, finally an admission, or slip-up, revealing that it’s just hyped-up coal and PVA glue! So not only will it burn in a fire, the glue will dissolve if it gets wet.
    Stay at home people, safety first.

  35. Comment by Gordon In Melb, Australia | 07.28.2010 | 9:01 pm

    Do I realli tipe that badd when I’m in a hurrrry

  36. Comment by Dr. Lammler | 07.28.2010 | 9:41 pm

    I have my doubts about this post.

    I just hacksawed my brand new Madone and couldn’t find a single ball bearing in the frame.

    But there are a lot of fibers.

  37. Comment by Steve | 07.29.2010 | 12:19 am

    I am so happy that I read this post! Your explanation completely clears the whole carbon fiber thing up for me. Thanks, Fatty!

    Cannonball Costanzo

  38. Comment by Mike Roadie | 07.29.2010 | 4:43 am

    So….if my bike floats, then it’s a duck???

  39. Comment by Jenn | 07.29.2010 | 4:49 am

    Professor Fatty,

    Where does ‘carbon dating’ fit in all of this? A match-making website for cyclists? A self-help tome promoting that the way to a man’s heart (via a pasta maker) is through his stomach…er…saddle…er, no, wait, that’s gross….

    Dateless in Deutschland

  40. Comment by Matthew in Seattle | 07.29.2010 | 5:21 am

    Paging the Real Dr. Lammler. Dr. Lammler to the information desk…

    Everyone knows that the real Dr. Lammler would not admit failure, having just sawed his brand new carbon fiber bicycle to bits. The real Dr. Lammler would make some sort of comments like:

    “My bike was my playground and evolved into my tool of making a living. This lasted 3 years until I realized I will never win a Tour de France. Then I took a tool to my playground and realized I would never be a master carpenter either.”

    “Why do you edit wikipedia???? Take a piece of paper and write it down!”

    or, “CARBON? Periodic Table of the Elements? Either you get it, or you don’t!!!!”

    To the fake Dr. Lammler, I find your lack of confrontational interrobangs to be the cause of your undoing.

  41. Comment by Cardiac Kid | 07.29.2010 | 5:50 am

    So to clarify there are ball bearings AND a motor in my downtube?

    I had no idea there was so much space in there….

  42. Comment by Dr. Lammler | 07.29.2010 | 9:00 am

    To Matthew in Seattle: A very good observation.

    Except my secret is not found in carbon fiber but in my luxury body.

  43. Comment by ging | 07.29.2010 | 11:21 am

    To funny…first your enlightening post, then your readers’ comments.

  44. Comment by Clydesteve | 07.29.2010 | 12:09 pm

    Listen, Fatty, there is still one thing I am hung up on.

    Do you boil the fibers strictly on time – 6 minutes – or do you toss them against the ceiling and see if they stick?

    Please hurry with an answer, both of my brothers will be over for dinner, and I want to be a perfect host.

  45. Comment by Dr. Lammler | 07.29.2010 | 2:27 pm

    I have continued my research and have learned the following:

    1. The top tube on a Scott Addict does not contain ball bearings.

    B. The owner of the Local Bike Shop does not share my enthusiasm for research.

    3. The policeman’s taser gun does not ignite carbon fiber.

  46. Comment by MrDaveyGie | 07.29.2010 | 6:37 pm

    Dear Mr. Fat cyclist.
    How much carbon fiber would it take to meet the Minimum Daily Requirement of Fiber.
    Thank you in advance.

  47. Comment by Karst | 07.29.2010 | 7:26 pm

    If the kids were home, they’d be worried why their Dad was rolling on the floor…laughing and shaking his head, wondering when Fatty was going to write about the perils of carbon fiber clothing.

    Fatty, how are you going to top this one?

    It may not be possible.

  48. Comment by MattyDC | 07.30.2010 | 7:28 am

    Fatty -

    You need a break from the blog, bro.

    Just step back. Slowly.

    Run re-runs until after Labor Day, or until you come up with something remotely or funny or interesting.

    Not hating on you, big fan.


  49. Comment by The other MattC | 08.1.2010 | 12:13 pm

    You realize you just destroyed some lazy junior high schoolers research for hir or her science project

  50. Comment by Mike | 11.7.2010 | 9:44 pm

    It’s true that carbon can fail catastrophically. The best thing you can do is thoroughly inspect joints and high stress areas before and after a ride. If you notice microcracking you can generally preemptively repair the damage by buying a small carbon fiber kit

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