Bike components made of carbon fiber have had a sketchy past that is ridden with both their positive and negative attributes. Nowadays, a carbon mountain bike is a fixture in many competitive biking events. When you go to bike store, a carbon frame is always offered alongside alloy types, although it comes with a premium price tag.
Carbon mountain bikes are very durable in general. The power-to-weight ratio is 18 percent higher than aluminum. High-end mountain bike frames can take up to 700 KSI (kilopound per square inch) before they snap.
But there’s more to it than that. While a carbon mountain bike has been synonymous to being lightweight, how come it such a durable material? Let’s find out.
What it Means to Have a Carbon Mountain Bike
There is a common misconception that a bike made of carbon fiber is not durable. I will refute that right off the bat. First of all, I will briefly discuss what carbon technology is.
A carbon bike is more aptly described as a bike with a carbon composite structure. This means the bike is not made of pure carbon; it also has several other components such as epoxy resin. Carbon is the reinforcing fiber that could be sourced either from glass or Kevlar. It is the epoxy resin that fuses them together.
In order to come up with high-quality carbon mountain bikes, advancements have been made in the manufacturing of stronger carbon filaments and their binder, which is resin.
There are two things that bike innovators want to achieve in a carbon mountain bike, and they are tensile strength and stiffness. A carbon filament’s strength is the amount of force required to break its fiber. Most high-end bikes are rated at 700 ksi (kilopound per square inch).
Stiffness, or modulus, on the other hand, can be categorized as standard, intermediate or high. It can be measured in terms of a million pounds per square inch.
It is interesting to note that tensile strength and modulus are not necessarily directly proportional to each other. Roughly speaking, a high modulus carbon fiber may tend to be weaker because of its stiffness. As such, a good carbon-fiber composite should strike a balance between these two important design elements to achieve optimal performance from a finished bike.
Aside from strength and stiffness, a carbon bike’s durability will also depend on the “prepeg”, which is the carbon raw material used, monocoque or bike structure, and the skill of the workers involved in manufacturing.
How Durable is a Carbon Bike
Testing a bike’s durability can be performed against standard use and exposure to the harshest conditions possible.
I have mentioned that a carbon bike is basically made from carbon-fiber composite. The specific strength or power-to-weight ratio is high, which is roughly 18 percent more than aluminum. This means the bike becomes more susceptible to extreme loads during an impact.
When a carbon mountain bike crashes, it neither bends nor dents, instead, it cracks. This damage can be invisible or visible. And this is probably why it has earned a bad rap in the durability department. Once the integrity of the composite is compromised, it becomes very fragile and therefore dangerous to continue using. As such, it should either be repaired or replaced.
Just like other materials, carbon will deteriorate with usage albeit, only after a long time. Carbon has the longest frame fatigue which enables many manufacturers to offer a lifetime warranty on frames made with this material. When aging happens, the resin matrix would be forming little cracks, and all that’s left are the connections of the fiber. The stiffness of the bike frame will slightly change in the process.
As for the different environmental conditions like your bike sitting under a hot, sunny weather, there is nothing that you should worry about. With bikes that are typically coated with UVA-resistant paint, they stand up against the scorching heat pretty well.
Ultimately, you can be assured that when you consider a carbon mountain bike, it will be a durable piece of equipment. As much as you can, you must avoid moderate to high impact on your bike, regardless of what material it is made of, for the sake of not only your bike, but also your own safety.
Other Notable Traits of a Carbon Mountain Bike
There’s more to it than just durability and strength. Carbon allows for more design options, reduces weight and offer a higher degree of stiffness. All these features come a at price though and not everyone thinks it’s worth the money.
The purpose of your carbon bike is a major design factor. Simply put, a bike that’s intended for enduro racing will look different than the one sold for trail riding. It may then have those nice curves and swooping form, which makes for a great-looking bike. Another example of a design difference would be the inclusion of aerodynamics for triathlon bikes, which you won’t typically find in a regular mountain bike.
Carbon-fiber composite allows more manipulation and usage such that it can produce complex bike designs. You will also find the cost of repairing carbon bike much less than anticipated.
Carbon-fiber frames are known for their lightweight features. It puts you at an advantage when you bike on steep terrain. There is less gravity and friction to deal with for the rider. It must be noted that there will be certain portions of the bike that will either be thick or thin depending on where strength and stiffness are needed the most.
Standard mountain bikes are constructed with broader tubes in order to absorb impact more effectively in case of an accident. This adds to the bulky weight of the bike that a carbon type is avoiding.
Comfort is a subjective factor. Carbon mountain bikes may have a high degree of stiffness, but they have the ability to reduce vibrations. This increases the comfort of riding in them, more so for road frames. The bike is engineered to be stiff in some directions and flexible in others, resulting in a compliant and smooth ride.
When you talk about carbon composite bikes, you are already certain that they are very expensive. You’d even wonder if it’s worth paying the extra thousand or two for a carbon bike that is only a pound lighter than an aluminum bike. But it’s easy to understand why it is more costly given the labor-intensive manufacturing process and specialized machinery it entails.
Durability of Other Frame Materials Used in Mountain Bikes
I remember MTB’s form the early days which were made of steel, they were heavy and I just can’t imagine riding one of these nowadays. Aluminium is still the best choice when it comes to budget and quality, slightly heavier than carbon but very reliable.
Aluminum (or aluminum alloy) bike frames are the most popular choice in mountain bikes. They are cheaper, especially when compared to carbon bikes. The weight is relatively light and has retained its design throughout the years.
A bike with a 6061 aluminum frame, for instance, is rust-resistant, making it low-maintenance that is ideal for many cyclists. Although alloy has the lowest strength among other types, it slightly compensates by using a thicker wall on the bike frame. What’s great is that doing so doesn’t add too much weight on the bike as a whole.
It is said that most mountain bikes come with a steel frame considering they were always preferred in the past. When you find one these days, you’ll notice it in a sea of bikes dominated by alloy and carbon by its retro charm.
When it comes to durability, a steel bike is arguably one of those that have a longer lifespan, considering that like carbon, it is repairable, too. However, there is a reason this is rarely seen in the roster of popular bikes – it is heavy such that it weighs thrice an alloy bike.
If there’s a bike frame that will rival the high cost of carbon composite, it’s titanium alloy. This may only be for those who dare to be different, but it is exceptionally durable, which can be considered a lifetime frame.
So yes, carbon mountain bikes are generally durable, and when properly cared for, you can enjoy riding it for many years. They are an expensive choice, but any bike that has great quality will really cost a pretty penny. Just remember that as a rider of any kind, pick the frame that suits you and essentially makes you the happiest.
I always had a thing for cycling sports and love almost anything that involves bikes and boards. I work part-time as a designer in the tech industry and work on my blogs whenever I can.