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A Cyclists Guide To Bike Frame Materials: Carbon Fibre

Carbon fibre-framed Team Sky time trial bike

Carbon fibre-framed Team Sky time trial bike

Welcome to the second in my series of posts on the materials used to make bicycle frames.

**UPDATE: The full list of ‘materials’ posts can be found on my new page dedicated to bike building: How To Build A Bike **

Readers of my previous article (which you can read here) will no doubt have been shocked, intrigued and ultimately delighted by my razor-sharp insights into the world of steel manufacture.

Now it is the turn of the young pretender to the throne: carbon fibre.

Virtually the entire professional road cycling world, and certainly all of the teams at the ProTeam level, use carbon fibre frames for their road race and time trial bikes. This would tend to suggest that, as a material, it has certain performance benefits.

So now, why don’t you join me, as we go … through … the … keyhole investigate the hi-tech carbon fibre industry.

What is carbon fibre?

Or carbon fiber, if your spelling is of a more American persuasion.

Carbon fibre is the shorthand term for carbon-fibre-reinforced polymer. Fibres are used to reinforce a polymer (normally expoxy) in order to create a light but very strong material suitable for making things that need to be, er, light and very strong.

The layout of the carbon fibres, and the proportion of carbon to polymer, allow manfacturers to vary the strength and rigidity of a piece of carbon fibre to suit its particular purpose.

How are carbon fibre frames constructed?

The individual pieces of carbon fibre are molded into their desired shapes. Once a mould has been created, sheets of carbon fibre cloth are layered within it and the epoxy is introduced. The contents of the mould are heated in order to bond the elements together.

As to how the bike frame itself is then constructed, the short answer is, ‘it depends’.

You can get carbon fibre tubes and lugs which are then joined together in much the same way as you would with steel tubing (albeit using glue rather than welding equipment).

Alternatively, you can form an entire section of the bike (for instance, the front triangle) using a single piece of carbon fibre before joining it to the other pieces of the frame.

A carbon buzz word that you often hear thrown around is ‘monocoque’. It sounds cool (very ‘racing car’) but is a bit of a misnomer in the cycling sense. Strictly speaking, monocoque refers to an object that derives its structural strength from its skin, rather than the underlying frame. Since a bike is only a frame, the word is a little nonsensical.

That said, the term is used to describe bikes that are made from a single piece of carbon fibre with no joins, such as the Lotus bike used by Chris Boardman to win gold at the 1992 Barcelona Olympics.

Presumably, to the Spanish, monocoque can also refer to the appendage of a male monkey.

Who makes carbon fibre for bikes?

The main suppliers of carbon fibre used to make bike frames and components are Japanese, and enjoy exciting names such as Toho Tenax, Toray Industrial and Mitsubishi Rayon.

The companies responsible for turning ‘raw’ carbon fibre into individual frames and components are almost entirely based in China and Taiwan. The manufacturers work with bike makers and designers around the world to implement their carbon visions.

Why do people choose carbon fibre for bicycle frames?

The two main arguments in favour of carbon fibre frames, at least from a professional racing perspective, are weight and aerodynamics.

All else being equal (and let’s face it, they rarely are equal), a carbon fibre frame will be lighter than an equivalent quality and strength steel (or titanium) frame.

The process of manufacture allows bike makers to produce frames sculpted to maximise aerodynamics. Using computer simulations and wind tunnel testing, frame (and other component) designers can adjust the shape of the bike to reduce air resistance and ultimately allow it to go faster.

The lightweight nature of carbon fibre means that such aerodynamic augmentations can have minimal impact in terms of increasing bike weight.

What are the limitations of carbon fibre as a frame material?

It is important how we define strength (i.e. in my description of the advantages of carbon fibre above). There are a number of properties that might come under the umbrella term, ‘strength’, in which carbon fibre underperforms other materials.

Carbon fibre is a less durable material than, for instance, steel. It is more likely to crack or shatter when something strikes it (or, more likely, when it, and you, strikes something else).

An important factor, particularly if you’re riding the bike at the time, is the speed at which the material fails. If steel receives a dent or a crack, it will generally continue to perform its function for a time. Carbon fibre, on the other hand, tends to fail ‘catastrophically’, which sounds… er, entertaining…

Fin

As I’ve already mentioned, this post is one of a series looking at all materials that are used to make bicycle frames (well, all sensible ones at least). If you’ve missed it, be sure to take a look at my barely-disguised love letter to steel (here’s the link again).

In future posts I’ll be looking at aluminium, titanium and wood, plus any other materials I discover in the meantime.

I do hope you’re finding the series interesting. Please do share it with your own personal peletons (or just click one of the buttons below).

I look forward to welcoming you back to the Grimpeur Heureux soon. Until then, I hope your road surface remains smooth and the wind is always at your back.

Chapeau!

Andrew

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{ 4 comments… add one }
  • Giles Roadnight May 7, 2013, 8:33 am

    Thanks for another good post. Definitely enjoying them. I am most looking forward to the more exotic materials such as Jelly and Ice! 😉

    • Andrew Montgomery May 8, 2013, 8:23 pm

      Thanks Giles. Glad you’re enjoying the posts. Not sure about Jelly and Ice cream, but bamboo will be on its way soon.

  • Jason Kansas July 11, 2013, 12:05 am

    As far as the uses of carbon fiber in bike uses, the rigidity of the material is most substantial. The minute flex in the frame from aluminum and other alloys takes efficiency and speed away from the rider. The weight only matters during acceleration and climbing.

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