In my last Gorilla Spun newsletter, I wrote about why I recommend hand-built wheels. Starting with this edition, I would like to delve a bit deeper into the world of wheel building, focusing on the components that make up a wheel and explaining their differences.
For the first installment, I’d like to talk about "spokes."
According to Google, "a spoke is one of the members that make up a wheel."
While not every wheel uses them—as there are disc wheels and baton wheels—they are an essential component in every wheel we build at Gorilla Spun.
Spokes come in a vast array of shapes and materials. When you add variations in length, thickness, and color to the mix, they are actually the component with the greatest variety in wheel construction.
Let’s take a closer look at each of these aspects.
First, shape.
There really are a great many types.
This is because the spokes used in factory-built wheels are almost always custom-designed for that specific wheel. While they offer no flexibility, they are designed to provide performance perfectly matched to that specific wheel system.
As I mentioned last time, this is the definitive difference between "hand-built" and "factory-built" wheels.
So, what kind of shapes do the spokes in hand-built wheels take?
Let’s start by looking at where they connect to the hub.
Broadly speaking, there are two types: "J-bend spokes" or "straight-pull spokes."
The pros and cons of each are:
J-bend spokes:
Most commercially available hubs are compatible with J-bend spokes, allowing for a wide selection of hubs. Because the head is bent, stress tends to concentrate there, so if a spoke breaks, it’s almost always at this point.
Straight-pull spokes:
Because there is no bent section, force isn't concentrated in one place, making them less prone to failure.
However, because there is no anchor point to hold them when tightening the nipple, the spoke can spin, making them difficult to adjust. Furthermore, they require specific hubs, so there are fewer options available.
That pretty much covers it.
Next, let’s look at the body of the spoke.
There are several types here as well: round spokes, aero spokes, and butted spokes.
Round spokes:
These have a circular cross-section and are the most commonly used type. They provide stable rigidity in all directions.
Aero spokes:
These flatten out into a shape resembling a flat noodle. By reducing the frontal projected area in the direction of rotation, they offer superior aerodynamics. Conversely, the side profile is wider, making them more susceptible to crosswinds, and they have lower lateral rigidity.
The thickness of the flat section varies, and some require hubs with specialized spoke holes.
Butted spokes:
The thickness of these round spokes changes along their length. While the degree of change varies by manufacturer and type, the main purpose is weight reduction by thinning the center. However, because they are thinner in the middle, that section is subject to more stress, making them slightly weaker than pure round spokes.
Furthermore, regarding butting methods, there is "single-butted" where it thins out once; "double-butted" where it thins out and then gets thicker again; and "triple-butted," where the thicknesses differ at the head, the center, and near the threading.
Also, the spoke thickness I’ve been mentioning is defined by JIS (Japanese Industrial Standards). For bicycles, gauges #12 through #15 are set. For sport bikes, #14 and #15 are used in almost all cases, while #13 is occasionally seen on downhill mountain bikes.
However, I have never personally worked with a #12 gauge spoke. Given that I have been involved with bicycles for nearly 25 years, it is safe to say they essentially don't exist in this context.
This difference in thickness naturally means that thicker spokes offer superior strength, while thinner ones are weaker. Conversely, thicker spokes are heavier, while thinner ones are lighter; therefore, it is important to strike the right balance for your intended use.
Material also plays a role in determining strength, but since this post is getting long, I will save that for next time.
Next time, I will talk about Spokes – Part 2 – Materials.