Carbon bicycles have become the majority standard in mid-high ranges and are, in general, the great aspiration of every cyclist who wants to upgrade their bike. The fame of carbon as a material for frame construction is such that, in the road cycling segment, it has completely displaced aluminum. At Tuvalum, for example, 9 out of 10 road bikes sold in 2021 had a carbon frame. And in mountain biking, although the gap between carbon and aluminum is narrower, the former also dominates sales from certain ranges upwards. But does this mean it's the only smart buying option? Has it stopped being worthwhile to buy an aluminum road bike? Do you really need to buy a carbon fiber bike? If you've asked yourself these questions, we're here to help you answer them. We analyze the pros and cons of this material in frame manufacturing and its real usefulness, depending on the type of cycling you practice.
A bit of history, when did carbon bikes emerge?
Carbon fiber began to be used in bicycle manufacturing in the late 1980s as an experimental material for road and time trial frame prototypes. Look was the main driving force behind this material for frame construction. This French brand took advantage of the large investment from the famous businessman Bernard Tapie, who bought the brand, to innovate in the development of new technologies for bicycles. Thus, in 1986, the first carbon bicycle in history was born: the Look KG 86, with which Greg Lemond won the Tour that same year. A model that combined carbon fiber with Kevlar and aluminum lugs to reduce weight and achieve better performance, especially when climbing mountain passes. Since then, several brands such as Bianchi, Lotus, or Vitus joined the manufacturing of carbon bikes in the early 1990s. This evolution was eventually joined by major manufacturers like Trek, Specialized, or Cannondale at the end of that decade and the early 2000s. These brands mass-produced models for both road and mountain biking, with more advanced molding techniques and the use of stiffer and stronger fibers.
Are all carbon frames the same?
This evolution in manufacturing processes brought with it different fiber compositions depending on the brand or model to enhance certain qualities depending on the type of cycling practiced or the area of the frame to be improved. You have probably heard of unidirectional UD fibers, 3K, and 12K, among others, but may not know how to tell them apart. They refer to the different composition and weaving of the fibers, enhancing some properties over others:
K Fibers (3K, 6K, 12K...)
This refers to the way the carbon is woven that makes up the frame tubes and components such as cranks, handlebars, etc. K fibers are responsible for the commercial boom of carbon bicycles, thanks to their cross weave that offers greater stiffness and consistency. As for the number, it refers to the thickness of this weave. 3K has 3,000 filaments per fiber; 6K has 6,000 filaments per fiber; 12K has 12,000 filaments per fiber, and so on. The more filaments the carbon has, the stronger and lighter the material is, since less epoxy resin is ultimately used for bonding.
When evaluating a carbon bike, it’s important to pay attention to the type of frame fibers (3K, 12K, unidirectional, etc)
UD Fibers
In recent seasons, unidirectional fiber carbon has become the most efficient carbon for manufacturing frames, especially in mid and high-end ranges. Unidirectional fibers—known as UD fibers—differ from K-type fibers in that they are all woven in one direction instead of being crossed. This means the frame needs less resin and the fibers act as a more solid and lighter block.
Advantages of Carbon Bicycles
The lightness/stiffness benefit is the main and most talked about one you’ve probably heard about carbon. But this material has other very interesting advantages. Let’s review the main ones:
1. Weight: lighter than aluminum
If you want a lightweight bike that won’t weigh you down when riding, climbing, etc., you inevitably have to look at carbon options. Another option if your budget is more limited is to improve your build by introducing some carbon components: handlebar, seatpost, cranks, wheels, etc. The average weight savings compared to an aluminum frame is significant, around 1 kg, although it can be greater depending on the model or brand. This doesn’t necessarily mean that all carbon bicycles are lighter than their aluminum equivalents, since the total weight of a bicycle doesn’t just depend on the frame, but also on other elements like wheels, drivetrain, wheels, etc.
2. Strength
The composition of carbon filaments is inherently very resistant to impacts and heat. And if we add their weave and bonding, we get very solid tubes that are also very resistant to impacts, heat, or corrosion. In the following video, you can see a resistance test of tubes made from different materials (steel, aluminum, kevlar...) where you can see the resistance of composite-type carbon fiber (common in frame manufacturing) compared to other metals.
3. Elasticity and absorption capacity
Its composition using threads bonded with resin (generally epoxy type) offers a flexible and absorbent structure. In addition, many manufacturers such as Cannondale or Trek play with the thickness of the fibers in certain areas of the frame (chainstays, seat stays, head tube) to absorb more or less impact from the terrain. Carbon, in general, is a material with which the geometry and shapes of the frame tubes can be varied to adapt to the specific needs of the cyclist. This gives it a greater ability to absorb irregularities in the asphalt and terrain and offer greater comfort to the cyclist.
4. Higher level of integration
This customization capability of the frame mentioned in the previous point allows the manufacture of frames with slimmer and smaller tubes than those made of aluminum, as well as playing with different profiles, shapes, or sections. The joints of the tubes are barely noticeable and components can be better integrated into it to achieve greater aerodynamic performance.
Disadvantages of carbon
It's not all advantages. Although carbon is a material that offers very high performance in terms of lightness, stiffness, and comfort, it also presents a series of drawbacks that must be taken into account when deciding between a carbon or aluminum bicycle. These are the main disadvantages:
1. The price: they are more expensive bikes
The cost of the raw carbon fiber material is higher than that of aluminum. It is more expensive to produce and process. In addition, molding and manufacturing frames or components is much more costly than materials like aluminum and steel. All of this affects the price. Currently, carbon is still reserved for mid-range and high-end bikes, with starting prices for new models of 1,700 euros and up for mountain or road bikes. If your budget is lower, an interesting option is to buy a second-hand carbon bike. To offset the high price of carbon, some brands resort to integrating lower-end components with their entry-level carbon frame models.
2. More expensive repairs
Carbon frame breakages do not occur as often as people think. It ends up being a material as strong or stronger than aluminum. However, in case of breakage, it is more fragile and its repair in the workshop is more complex and expensive. This is a point to consider, although with some basic and frequent care you can reduce the chances of breakage.
3. Greater sensitivity to friction and tightening torques
One of the most common cracks in carbon frames occurs due to excessive tightening of the seatpost clamp on the frame. Although carbon is a very stiff and strong material, this hardness means that more care must be taken when assembling other components. That is why it is essential to use special assembly paste or grease for carbon when assembling a seatpost or handlebar. Likewise, when tightening bolts, it is very important to respect the torque (expressed in Nm) provided by the manufacturer. If you overtighten, the possibility of cracking or breaking may be greater than in an aluminum frame.
4. Non-recyclable material
Another disadvantage that is not trivial is the carbon footprint generated by carbon. Manufacturing a bicycle frame from this material requires more energy and generates more waste than aluminum or steel. In addition, unlike these latter materials, carbon is very difficult to recycle. Once degraded, only part of the epoxy resin in its composition can be recycled; the rest is highly polluting and usually ends up rotting in landfills or even in rivers and seas.
Myths and legends about carbon frames
Carbon fiber as the star material in bicycle manufacturing is surrounded by a multitude of myths and legends that should be debunked. When looking at buying options, do not let yourself be influenced by these kinds of clichés and look for truthful and verified information from established brands, specialized media, engineering studies, etc.
Myth 1: Carbon is more fragile than aluminum
This statement is a half-truth that needs clarification. Various impact resistance tests give composite carbon fiber greater strength than steel or aluminum alloy. Likewise, its resistance to corrosion and temperature changes is also superior. In general, it is better insulated from the outside. This means that the degradation or risk of breakage due to wear of quality carbon is lower compared to an equivalent frame in aluminum or steel. However, precisely because of its greater rigidity and strength, in the event of a direct high-impact blow, carbon does not deform but tends to crack. Hence the assumption that it is more fragile than aluminum.
Myth 2: It only has benefits in competition
This is a myth that is fortunately being left behind more and more. Although there are still many cyclists who believe that there are no substantial differences for amateur use of the bicycle. As we have already explained, carbon not only provides greater lightness and better levels of stiffness, which are useful in changes of pace or to generate more watts. It also provides comfort and absorption when overcoming obstacles and riding on rough terrain. This myth is easy to dispel: try riding 100 kilometers on an aluminum bike and compare it to doing the same route on a carbon bike. With equal components and assembly, the carbon bike offers greater comfort on long rides.
Myth 3: Carbon needs more care
Carbon may be more sensitive when assembling components. But beyond using specific assembly grease and not overtightening, it requires practically the same care as other materials like aluminum or steel. In fact, it may even require less, since it is not prone to oxidation or corrosion.
Conclusions
Disadvantages of carbon
Not everything is an advantage. Although carbon is a material that offers very high performance in terms of lightness, stiffness, and comfort, it also has a series of drawbacks that must be taken into account when deciding between a carbon or aluminum bike. These are the main disadvantages:
1. Price: they are more expensive bikes
The cost of carbon fiber raw material is higher than that of aluminum. It is more expensive to produce and process. In addition, molding and manufacturing frames or components is much more costly than with materials like aluminum or steel. All of this affects the price. Currently, carbon is still reserved for mid-range and high-end bikes, with starting prices for new mountain or road models from 1,700 euros and up. If your budget is lower, an interesting option is to buy a second-hand carbon bike. To offset the high price of carbon, some brands choose to integrate lower-end components with their entry-level carbon frame bikes.
2. More expensive repairs
Breakages of carbon frames do not occur as often as people think. It ends up being a material as strong or even stronger than aluminum. However, in the event of a break, the fragility is greater and repair in the workshop is more complex and expensive. This is something to consider, although with some basic and frequent care you can reduce the chances of breakage.
3. Greater sensitivity to friction and tightening torques
One of the most common cracks in carbon frames occurs from overtightening the seatpost clamp on the frame. Although carbon is a very stiff and strong material, this hardness means you need to be more careful when assembling other components. That’s why it’s essential to use special assembly paste or grease for carbon when installing a seatpost or handlebar. Likewise, when screwing in, it’s very important to respect the tightening torque (expressed in Nm) provided by the manufacturer. If you overtighten, the possibility of cracks or breakage can be higher than in an aluminum frame.
4. Non-recyclable material
Another disadvantage that is not trivial is the carbon footprint generated by carbon. Manufacturing a bicycle frame from this material consumes more energy and produces more waste than aluminum or steel. Furthermore, unlike those other materials, carbon is very difficult to recycle. Once degraded, only part of the epoxy resin in its composition can be recycled; the rest is highly polluting and usually ends up rotting in landfills or even in rivers and seas.
Myths and legends about carbon frames
Carbon fiber as the star material in bicycle manufacturing is surrounded by a multitude of myths and legends that should be debunked. When considering purchase options, don't let yourself be influenced by these kinds of clichés and look for truthful and verified information from established brands, specialized media, engineering studies, etc.
Myth 1: Carbon is more fragile than aluminum
This statement is a half-truth that needs clarification. Various impact resistance tests give composite carbon fiber greater strength than steel or aluminum alloy. Likewise, its resistance to corrosion and temperature changes is also superior. In general, it is more isolated from the outside. This means that the degradation or risk of breakage due to wear of quality carbon is lower compared to an equivalent aluminum or steel frame. However, precisely because of its greater stiffness and strength, in the event of a direct high-power impact, carbon does not deform but tends to crack. Hence the assumption that it is more fragile than aluminum.
Myth 2: It only has benefits in competition
This is a myth that is fortunately being banished more and more. Although there are still many cyclists who believe there are no substantial differences for amateur use of the bicycle. As we have already explained, carbon not only provides greater lightness and better levels of stiffness, which are advantageous for changes in pace or generating more watts. It also provides comfort and absorption when overcoming obstacles and riding on rough terrain. This myth is easy to dispel: try riding 100 kilometers with an aluminum bike and compare it to doing the same route on a carbon bike. With equal components and setup, the carbon bike offers greater comfort on long rides.
Myth 3: Carbon needs more care
Carbon may be more sensitive when assembling components. But beyond using specific assembly grease and not overtightening, it requires practically the same care as other materials like aluminum or steel. Even less, since it is not prone to oxidation or corrosion.
Conclusions
Once we have reviewed the characteristics of carbon, we are left to answer the question with which we opened this article. Without a doubt, a carbon bicycle ends up having many more pros than cons compared to an aluminum bicycle. We can advise you to buy a carbon bicycle if you are really serious about cycling and want to gain in performance and comfort. The investment, which is increasingly affordable due to its widespread use in more economical ranges, ends up being worthwhile in every aspect and for all disciplines. Even the most radical ones in mountain biking, such as enduro or downhill. However, we do not recommend this type of bicycle if you are going to ride occasionally or for short, easy routes without major sporting goals, where there is less need to go fast. Nor for uses that are not strictly sporting, such as commuting from home to work in the city. For everything else, we say yes to carbon.