Introduction
One of the latest trends in carbon road and gravel wheels is the emergence of carbon spokes. Traditionally, wheels have used steel spokes, but due to advancements, there are now multiple options. In this article we will explore some of the differences, and look into the future of carbon spokes as a technology.
Steel Spoke Design
Most steel spokes now are straight pull, rather than J-bend. Straight pull spokes can be lighter and suffer from less fatigue, as the bending of a metal makes it more fragile. Steel spokes have been proven reliable and are very mature as a technology. They can even be made lightweight, with some spokes such as Sapim CX-Ray spokes coming in at only 4.4 grams each. Steel spokes can have a rounded profile or an aero bladed one, though this shape is somewhat limited as it is difficult to make more complex shapes with steel without compromising integrity and adding a significant amount of material.
Carbon Spoke Design
Carbon spokes started out in triathlons and time trial wheels, where each wheel had 3 or four large spokes. These wheels are not particularly practical for regular road or gravel riding. They did however offer benefits when it came to aerodynamics. Later, more traditional wheels with a larger number of spokes. While these wheels became more practical for the everyday rider, they had a significant flaw. A single broken spoke or rim would mean the entire rim was compromised and had to be thrown away. This is because the spoke was bonded to both the hub and the rims.
Newer carbon spokes can now be replaced just as easily as steel spokes, making them convenient and significantly less wasteful.
The Main Differences
When comparing steel spokes and replaceable carbon spokes, there are a few things that separate the two.
Price
Due to production costs, carbon spokes are more expensive to produce, and in some cases much more expensive to produce. Just like carbon rims are much more expensive and labor-intensive to produce than alloy rims, the same thing is true with spokes. In addition, due to economies of scale and research and development, the latest generation carbon spokes are even more expensive.
Weight
Carbon spokes can be made significantly lighter than even the lightest steel spokes. 2nd and 3rd generation carbon spokes weight roughly three grams each, while 4th generation spokes weigh roughly two grams each. The lightest steel spokes like Sapim CX-Ray weigh 4.4 grams each.
Responsiveness
Carbon spokes are significantly stiffer than the equivalent steel spoke. This means that you get improved power transfer. In order to balance things out fewer spokes are needed to achieve the same strength and stiffness, allowing for fewer to be used.
Durability
One commonly held belief is that steel spokes are safer than carbon spokes. Now, in general, this is not the case. Bonded spokes are much more likely to fail due to imperfections and lack of uniformity as well as those of earlier designs. Now, replaceable carbon spokes have been a game changer. They can survive the toughest races in WorldTour races. They also have much higher torsional strength than steel spokes. Of course they can break in a crash, but so do steel spokes. After years of working with carbon spokes and talking to pro bike teams as well as customers, we are confident that carbon spokes are just as reliable and safe as steel spokes.
Comparing Carbon Spokes
While steel spokes are a very mature technology, carbon spokes are being revolutionized and improving with every iteration. Let’s dive into how carbon spokes have changed and which ones we use on our wheels.
First Generation Carbon Spokes
First generation spokes are what most people are familiar with. These spokes were bonded to both the hub and the rim. They were groundbreaking and led the way for things to come. They did have several major drawbacks like a lack of repairability, high cost, and higher rates of failure, but they are very cool. There is something special about a monocoque carbon wheel. While these are slowly being fazed out in favor of replaceable spoke designs, they are still an important part of many modern wheels, including trispokes for TT and triathlon events.
Second Generation Carbon Spokes
Once second generation carbon spokes hit the market, they were instantly a game changer. Now, carbon spoke wheels could be much more easily manufactured and with a greater margin of safety due to uniformity. These are the predominant spoke used on carbon spoke wheels today. They can be replaced just as easy as regular steel spokes. Their rims did need custom spoke hole drilling at specific angles so that spokes do not contact one another.
There are a few drawbacks to 2nd generation spokes over newer generations. The first is that they all use round spoke heads. This means that they could very easily experience spoke twist, leading to worsened aerodynamic performance. In addition, since 2nd generation spokes were relatively new, quality control problems were more likely.
Additionally, these hub designs tended to have open flanges, which meant that a loss of spoke tension could cause spokes to become dislodged. While rare, this was a possibility and was worrisome for many riders.
Third Generation Carbon Spokes
What separates the third generation of spokes from the ones before is that they can now be mechanically secured, meaning that they do not experience spoke twist. This offers a big aerodynamic advantage over second generation spokes. While these spokes are becoming more common, they are still the minority. Specially designed hubs are also required to use third generation spokes. Some of these hub designs, including ours, completely eliminates the possibility of spokes becoming dislodged.
Fourth Generation Carbon Spokes
As of now, only a few brands have started to adopt fourth generation spokes. The main advantages fourth generation spokes have over their second and third generation counterparts are twofold. These new spokes are more than 50% lighter, putting them in at around only two grams each with nipples. Ours achieve such low weights partially due to using titanium thread pieces and spoke heads. Furthermore, they offer a significant amount of additional compliance, giving them the ride characteristics of steel spokes. We use the lightest spokes available, making them even lighter than Berd spokes.