Manufacturers have been producing bicycles with frames and forks made of different materials for quite a while now. The most common combination is an aluminum frame paired with a carbon fork.
Carbon forks are chosen over classic metal options to minimize the bike’s weight and improve the rider’s comfort thanks to carbon’s absorption properties. By relying on carbon only for the fork, manufacturers lower the production costs and provide an affordable machine satisfying the public’s fascination with the new age material.
What Are The Main Benefits of a Carbon Fork?
Carbon has a crystalline structure. This means that the molecules and atoms forming it are held together in a highly ordered three-dimensional pattern which results in great structural integrity.
This sophisticated architecture allows carbon to sustain a lot of tension before breaking while simultaneously having a notably lower density and consequently weight than steel, aluminum, and titanium.
The Density of Carbon, Steel and Aluminum
|Carbon fiber||1.78 g/cm3|
The table above reveals the following:
- Carbon has a roughly 35% lower density than aluminum.
- Steel is 4.4 times denser and heavier than carbon.
Therefore, in theory, if the dimensions of a component are preserved, but it’s built of carbon instead of aluminum, the weight of the element would drop by 35%.
If the same is done to replace a component originally made of steel, the weight should decrease 4.4 times.
However, the production process isn’t that simple. Additional carbon fibers might be added to strengthen an element. The extra support increases the weight of the product.
Ultimately, the weight reduction that carbon can provide is around 20-50%.
For instance, a light Chromoly MTB fork weighs approximately 1080 grams (e.g., Salsa CroMoto Grande) whereas one made of carbon is 660g (e.g., Ritchey WCS Carbon). The Ritchey Carbon fork is 39% lighter.
The reduction would be even greater if steel of lesser quality (e.g., hi-ten steel) is used in the comparison.
If we compare a steel road fork to a carbon one, the weight savings rise even more because road forks don’t have to be as strong as those designed for off-road.
For example, Surly Steamroller 28″/700c (Chromoly) weighs around 1000 grams whereas the Ritchey Comp Carbon Road Fork is approximately 540g – almost a 50% difference.
The table below compares the weight of more mountain bike, trekking, and touring forks made of steel and carbon.
|Surly ECR Disc 29″ MTB Rigid Fork||1400g||Salsa Firestarter Deluxe Carbon 29″||620g|
|Surly Krampus Disc 29″ MTB||1180g||MRP Rock Solid MTB Fork Disc 29″||725g|
|Identiti XCT||1630g||ENVE Fork MTB 2019||719g|
What about aluminum?
Aluminum forks are significantly lighter than those made of steel but still slightly heavier than the carbon options.
The next table contains aluminum forks designed for MTB, trekking, and touring.
|Kinesis CrossWind 413 Disc 28″||710g|
|Kinesis Maxlight 475 Disc 26″/27.5″ MTB||874g|
|Salsa Beargrease 26″ MTB Fatbike Rigid Fork||740g|
The structural geometry of carbon has given it a high modulus of elasticity – the quantity measuring an object’s resistance to elastic deformation.
The tensile modulus is measured in pounds of force per square inch of cross-sectional area (psi) and in the case of carbon fiber it ranges between 34.8- 145.0 million psi.
Meanwhile, the tensile modulus of steel is approximately 29 million psi whereas that of aluminum is about 10 million psi.
Therefore, carbon has the potential to be many times stronger than steel and aluminum.
Road Absorption and Compliance
Carbon forks could be engineered according to the needs of the rider. They could be made stiffer or more compliant by altering the design and placing different grades of carbon at certain locations.
In general, the goal is to make the fork as stable as possible laterally and more compliant vertically.
FAQ: Can’t the same be achieved with steel and aluminum?
Steel forks are springy and certainly enough for many consumers. They lose to carbon forks not because they aren’t compliant, but because they’re heavier.
Aluminum, on the other hand, is lighter than steel, but it’s also less compliant than both carbon and steel and provides a harsher ride.
However, aluminum components have gotten better over the years. Newer aluminum forks and frames are surprisingly soft. Hence why many people believe that a lot of aluminum’s bad reputation is due to the less sophisticated production processes used initially.
Carbon allows the production of forks with aerodynamic shapes without negatively impacting the strength and weight saving properties of the element. Hence why many carbon forks look futuristic.
Long Shelf Life
Unlike metal, carbon components do not degrade over time. Consequently, they could potentially have a very long shelf life if they aren’t damaged in an accident and receive proper and consistent care.
Aluminum Frame + Carbon Fork = Affordable Lightweight Bike
By combining a light aluminum frame with a carbon fork, one can produce a very light bike for a lot less money than if the entire bike was made out of carbon.
This strategy combines the benefits of aluminum (low price + low weight) and carbon (low weight + compliance) while minimizing production costs.
Conversely, putting a carbon fork on a steel bike makes less sense for two reasons:
- A steel bike could be very light, but that property comes at a higher price. Hence why we find aluminum frames on most consumer models.
- A nice steel fork already has the damping capabilities that a carbon fork can offer.
Other Incentives Behind Carbon Forks
Carbon’s properties are not the only reason to pair carbon forks with frames of different materials.
The motivation behind this decision includes the following points too:
Ease of Production
Forks are an independent and fairly small component. Those traits create a favorable condition to produce them out of a different material.
Also, forks are significantly easier to manufacture than a frame because they are of smaller size and have a less complicated shape to mold. This property facilitates mass production.
Since the fork has a direct and easily perceivable effect on the level of comfort, making it out of carbon is a great way to implement the benefits of the material while using as little of it as possible.
Carbon is a fashionable material used for the production of aircraft and spaceships. By making a carbon fork, manufacturers add “cool points” to their low and mid-range models while keeping the bicycles affordable.
This marketing maneuver may not affect the experienced cyclists who know that a cheap carbon fork isn’t necessarily better than steel and aluminum ones, but the beginners are often impressed upon learning that they can get a carbon component with their entry-level bike.
Stylish, High-Quality Look For Cheap
To determine the quality of a carbon component, one has to scan or cut it. Hence why even the cheapest carbon forks can have a very elegant and expensive look to them. This peculiarity boosts the appeal of carbon forks even more.
What Are the Downsides of Carbon Forks?
The quality of carbon components has increased greatly over the past decade. Nonetheless, the material has some inherent downsides:
Low Impact Resilience
Carbon fiber may have a higher tensile strength than steel, but it can’t take external hits nearly as well because it lacks density and robustness. As a result, carbon components require frequent inspections to ensure that the integrity of the composite has not been disrupted.
Carbon’s poor ability to deal with direct impact is why commuting with a carbon bicycle isn’t the most sensible strategy.
If you lock a carbon bike at a busy bike rack, someone might easily scratch it or even put a dent in it while locking their bicycle. And all that could happen without the other person even realizing it.
Meanwhile, steel and even aluminum can get scratched and hit a lot more without suffering from fatal degradation.
For the same reason, steel components have been the preferred choice of commuters for a long time. They can survive a monumental amount of abuse, scratches, and hits while preserving their structural integrity. Moreover, they do not demand nearly as frequent inspections as carbon.
Carbon fiber components require more intensive care to avoid catastrophic consequences.
For example, one must tighten the stem bolts with a torque wrench to the required specifications. If that’s not done, the stem may crush the steerer tube because carbon is hollow and doesn’t deal very well with compressing forces.
Most beginner cyclists may fail at this task simply because they are ignorant of the subject. Truth be told, most people don’t even know what a torque wrench is in the first place.
In addition, carbon components require special grease designed for carbon. You’ll also need a special carbon-specific blade to cut the steerer tube.
When you add the necessity for frequent examinations, you have a recipe for a beginner unfriendly component. This alone is enough to push away some of the crowd simply because most people don’t take the maintenance of their bike as seriously as dedicated cyclists.
Contrariwise, steel and aluminum are more forgiving and thus beginner-friendly.
FAQ: Why does carbon require frequent examinations?
Because the composite is strong only when its integrity is preserved completely.
Moreover, when carbon fails, it does so without great signs of warning. And when it breaks, it breaks for real.
Of course, sudden failure can happen even to a steel component, but the chances of that scenario are far greater with carbon fiber.
As a consequence, careful examination of every carbon component is necessary, especially after a collision or very aggressive riding.
Some of the carbon forks in the tables above are over USD 500 because carbon costs USD 10-20+ per pound, and the production process is complicated and labor-intensive.
For half that, one can buy a very decent Chromoly or aluminum fork.
Of course, there are also significantly cheaper carbon forks, but the quality isn’t always up to par, and the performance that one expects of the material isn’t there.
Hence why it’s often better to purchase a steel or aluminum fork produced from a reputable company than to go for a carbon one made by an unknown manufacturer.
Having said that, the prices of decent carbon forks are going down.
Frequently Asked Questions
Why do some carbon forks have aluminum steerer tubes?
Aluminum steerers on carbon forks are there mainly to cut production costs and lower the price of the fork.
Another benefit of alloy steerers is that they are more resistant to compression. As a consequence, the clamping force of the stem is less likely to crush the tube.
Is it worth it to upgrade my bike with a carbon fork?
It could be if the rest of the bike matches it. Putting an expensive carbon fork on a cheap bike is impractical and so is replacing a high-end aluminum or steel fork with a low-end carbon one.
Furthermore, in some cases, the vibration softening that carbon provides can be achieved by simply lowering the tire pressure (if possible) or switching to wider tires that can run at lower pressure.
Would it be worth it to repair a broken carbon fork?
Yes, but only if the price of the repair is noticeably lower than buying a new fork. Also, the work has to be done by a composite shop with skilled people in it. Otherwise, it would be wiser to replace the fork with a new one.
Grimes, G., 1992. Composite Materials. Philadelphia: ASTM.
Elert, Glenn. “Density of Steel”. Retrieved 2020-06-03.
Bajpai, P., 2017. Carbon Fibre From Lignin. 1st ed. Springer, pp.19, 20.