RSR Moto's Guide to Motorcycle Carbon Fibre

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A graphite polymer
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A graphite polymer

What is Carbon Fibre?

Carbon fibre is made from graphite - a chemically pure form of carbon. It is a polymer in which the carbon atoms are arranged hexagonally, in long thin sheets, that can be thought of as ribbons. When these ribbons are packed tightly together, you have carbon fibre.

These fibres themselves are flexible and can’t, on their own, be used to form rigid structures. Instead, they are used to reinforce other materials like epoxy resins and other types of thermosetting compounds. These materials, when combined with carbon fibre weave, are known as composites because they have more than one component.

Carbon fibre reinforced composites are incredibly strong and light. They're five times stronger than steel, twice as stiff, and one-third the weight. Carbon Fibre can be used to replace metals and plastics in a variety of applications where strength and light weight are crucial. 

Applying pre-preg carbon to the mold
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Applying pre-preg carbon to the mold

How Carbon Fibre is Made

There are two main ways of making carbon fibre parts: wet lay up and autoclave pre-preg.

Wet Lay Up
Wet lay up involves placing dry carbon matting into a mould and then coating it with resin. Further layers of matting and resin are added as required. The resin impregnated matting is then sealed in a vacuum bag and is  baked in an oven or autoclave. Once out of the oven/autoclave, the last stage in the process is trimming and the application of UV lacquer. It is possible to make carbon fibre parts at home using this process but we wouldn't recommend it.

This method has two major disadvantages. The first is that the final product is relatively heavy due to the repeated build up of layers of matting and epoxy. The second is that it tends to have a less attractive finish due to air bubbles being trapped in the fabric. It is does, however, have the advantage that it is cheaper. RSR Moto do not sell wet layup carbon fibre. Read on to find out about our process.

Autoclave Pre-Preg

The main difference here is that pre-preg fabric already has the resin within it. Because the process doesn’t involve applying resin to dry carbon matting, there are no unsightly air bubbles.

As with wet lay up, the carbon matting is layered into the mould. Once in the mold, the fabric is heated under pressure in an autoclave for up to eight hours. When the product has been removed from the autoclave, it is trimmed to remove excess material. Finally, it is treated with UV-resistant lacquer. 

The finished product is lighter, stronger, and better finished with none of the flaws found in wet lay up - an important consideration when adding carbon parts to our beloved motorcycles

A major issue for the manufacturer is that pre-preg has to be kept in a freezer to prevent the resin from hardening. This has significant cost implications, which leads us to our next topic.
An autoclave as used by one of our suppliers
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An autoclave as used by one of our suppliers
Making strands from raw carbon
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Making strands from raw carbon

Why Carbon Fibre is Expensive

There are two reasons for this: the highly complex manufacturing process and the cost of the materials. 

The raw carbon itself comes in blocks and is not expensive at around £3/kilo. However, processing it into the strands of carbon that make up the carbon weave is a costly process. The manufacturer needs to invest in costly machines to draw the carbon our into lengthy filaments, and ovens capable of taking the materials through three heat cycles at over 1000 degrees celsius. As you can imagine, the power bills are significant. 

The next stage is weaving the carbon into sheets. This is a lengthy, high precision process that again requires massive, energy hungry machines. One square metre of good quality finished carbon fibre sheet costs around £75.

The process of manufacturing the part itself is  an extremely exacting process that can only be done by hand. The addition of UV resistant lacquer, and hand finishing and polishing the part, further add to the cost. 

Despite the cost, the unique advantages of carbon fibre - its strength, stiffness and light weight - mean it is ideal for a wide range of applications. Add in its attractive appearance and the appeal for the motorcyclist is easy to understand.
Twill weave carbon fibre
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Twill weave carbon fibre

Different Carbon Fibre Weaves

2/2 Twill Weave

The most common type of carbon fibre used on motorcycles is ‘2/2 Twill’. Here, the weft goes over two intersecting warps, then under two more etc, giving the 2/2 weave its name. The result is a diagonal pattern in the finished product.

This type of carbon fibre is mainly associated with Aprilia, BMW, Honda, Kawasaki, Suzuki and Yamaha.

Plain Weave

Plain weave is the second most common type of carbon fabric. In this weave, the weft passes over one weave, under the next and so on, creating a pattern that resembles a grid.

Plain weave carbon fibre is the type mainly found on Ducatis and MV Agustas.

The most important consideration when choosing carbon fibre for your bike is simply to choose the type of weave you like best.

Other Weaves

Carbon fabric is also available in harness weave, basket weave, leno weave and several other varieties. These obscure patterns can suffer from stability issues and are hardly ever seen in motorcycle/automotive applications. 

Check out our range of top quality pre-preg autoclave manufactured carbon

G
lossary of Terms

Autoclave: A heated container used for initiating and maintaining chemical reactions and other processes using high pressures and temperatures.

Carbon: Chemical element with the atomic number 6. A non-metal which has two main forms (diamond and graphite). It also occurs in impure form in charcoal, soot, and coal. Chemical symbol: C

Epoxy Resin: An adhesive material made from a class of synthetic thermosetting polymers.

Graphite: A grey crystalline form of carbon which occurs as a mineral in some rocks. Can also be made from coke. Uses include: as a solid lubricant; in pencils; as a moderator in nuclear reactors and, of course, making carbon fibre parts for RSR Moto.

Polymer: A substance with a molecular structure built up from a large number of similar units bonded together, e.g. synthetic materials used as plastics and resins.

Thermosetting: Denoting substances (especially synthetic resins) which set permanently when heated. In the manufacture of carbon fibre parts, the thermosetting takes place in the autoclave.

Warp & Weft: The threads on a loom over and under which other threads (the weft) are passed to make cloth.

Check out our range of best quality 100% autoclave pre-preg carbon fibre.

Plain weave carbon fibre is the type usually found on Ducatis and MV Agustas. 
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