Why Do Bicycles Have Spokes?

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Why do bicycles have spokes?

Bike spokes to bikes are like the unassuming cousins to a family gathering. They hardly take center stage but keep everything going smoothly from the background.

Imagine a bike in your mind. Does your imaginary bike have spoked wheels? It probably does. But do they have a real purpose or are they just charming decorations?

This article will tell you all about bike spokes and how they play an essential but often overlooked role in the functions of a bike. They look pretty simple but there’s actually a lot of Science that goes into their development.

Bicycles have spokes because they are a cheap and ingenious way to make light, yet remarkably strong wheels that are not sensitive to crosswind. Spokes support wheel structure and play a huge role in the bike’s maneuverability, flexibility and shock resistance.

What’s a Spoke?

A spoke is one of many long, thin rods weaved together that go between the wheel hub and rim. The hub is at the wheel’s center and has an axle and bearing for rotation. The rim is the circular frame. Spokes tie these two bike parts together.

How do They Work?

Spokes are akin to very long screws that act like springy torsion bars. They hold the shape of the wheel and receives the highest stress. The spokes pull the rim towards the hub, and they must all be equal in length and apply equal tension for the wheel to remain true.

A wobbly wheel is said to be out‐of‐true and is difficult to maneuver and can even cause you to crash. In addition, uneven or too high tension can ruin the bike rim.

An out-of-true wheel can be fixed by truing. Truing in bikes is the process of adjusting the spoke tension that pulls on the rim so they are even and incorrect alignment.

Spokes are pulled very tightly towards the rim and sustain the great but uniform tension that act like a preloaded spring. If you put a load on the bike‒namely, your body — it’s this tension that allows the wheel to bear your weight without getting bent out of shape.

The extreme tension makes spokes responsible for making wheels very strong without sacrificing lightness.

Bicycle Spoke Size and Shape

Bicycle spokes usually have a diameter of 1.8 or 2.0 mm. That’s 15 and 14 gauge, respectively. Larger gauge numbers equal a thinner spoke.

Most spokes are made of stainless steel. Galvanized steel may be seen on older or cheaper bikes. Titanium spokes are around but they are excessively expensive. Aluminum and carbon fiber spokes are not unheard of but they are rare and are sort of impractical.

A spoke starts life as part of a massive, continuous roll of wire. The wire is then unrolled, straightened and cut into precise lengths. A head is formed on one end of the cut piece.

For j‐bend spokes, they are bent into an elbow to more than a 90-degree angle so it’ll fit the inside and outside of a hub. Straight pull spokes do not have this bend. From this point on, the process diverges depending on the type of spoke made.

Straight Gauge Spokes

That’s pretty much it for the straight gauge spoke. They are cheap because they are so simple to manufacture.

As the name suggests, straight gauge spokes maintain a uniform gauge or thickness from end to end. They don’t last as long as other types of spokes as their straightness give a little less resistance to fatigue.

Straight gauge spokes are ideal for heavy‐duty bicycles like mountain bikes where weight‐saving is not a primary priority.

Swaged Spokes

You may also hear the term Double‐butted or Butted when referring to this type of spoke. The terms come down to the process of manufacturing.

Double butted spokes have the ends made thicker while with swaged spokes, it’s the middle that’s made thinner. These spokes come in varied dimensions and thickness.

Swaged spokes are created by taking a regular spoke and drawing it with a reducing die. This reduction in diameter increases elasticity, adds strength and reduces weight. It also transfers stress to the spoke’s midsection, allowing for efficient absorption of high-frequency vibrations in the road. All this translates to a more responsive ride and a higher fatigue life.

Swaged spokes are more long‐lasting than their straight counterpart. However, these spokes are also more expensive to produce and a bit more difficult to true. They’re ideal for road bikes that are made for regular use with consideration to speed.

Bladed Spokes

This spoke starts out as a regular spoke that’s drawn into a swaged spoke, then flattened into a flat blade. This process makes it a very light and responsive spoke with high fatigue life. The flat blade slices through the air which reduces wind drag and saves valuable seconds.

The downside to this type of spoke is that they can be 3‐5 times more expensive than round spokes and are less resistant to twisting. When this happens, the flat side is twisted to face the wind instead of the blade, thereby,  increasing wind drag instead of reducing it. For this reason, bladed spokes are not advisable for general cycling use.

Bladed spokes are sometimes referred to as “Aero spokes”. They are used in aero bikes, short for aerodynamic bikes, which are a type of bike usually meant for bike racers and short course triathletes.

These bikes apply the principles of aerodynamics for increased speed and they come with specialized frames, aero wheels that have aero spokes attached to aero rims, and even aero helmets and aero clothing, etc.

There is also an aerodynamic position that riders have to take in order to effectively reap the speed benefits.

How Many Spokes Are On a Bike?

Wheels can have any number of spokes but traditional bike wheels commonly have 28, 32 or 36. The old standard sometimes has a front wheel with fewer spokes than the rear wheel, although nowadays, equal numbers are quite common.

The number can actually vary primarily depending on the purpose, but also style, year and even the country of origin.

A high spoke count usually equals stronger and more durable wheels. What basically happens is that the load can be distributed evenly among more spokes, thereby lowering the cyclic stress on each spoke.

Add in a criss‐cross lacing pattern and you got yourself a stiff, robust wheel that will take you long distances and are great for traveling on rough terrain. Lacing patterns will be discussed in the next section.

Aero Wheels, on the other hand, have fewer spokes that are usually bladed. The lesser number of spokes is ascribed to the principle that fewer spokes equal lesser wind drag. These are the wheels that can have 24‐28 and can even go down to 16 or even 12.

The catch is that the spokes have to be made of stronger material to support the accompanying cyclic stress. These materials can be heavier than ordinary steel spokes. The idea is that the reduced number compensates for the heavier material.

Then, there’s the disc wheel that does not have spokes but a covered or solid wheel and reduces even more wind drag than wheels with few spokes.

How are Spokes Arranged on a Wheel?

Even the way spokes are installed on a wheel influences the wheel’s stiffness, strength and weight.

The 3‐cross or 3X lacing pattern is the most common and means that a spoke crosses 3 other spokes as it connects the hub and rim. Bikes for general use often have this pattern.

More lacings use longer spokes because the criss-cross means more distance from the rim to the hub. This also means more weight and strength but marginally lesser speed.

Mountain bikes, because they are made for tougher roads, may use 3X or even a 4X pattern. The 2X and 1x patterns are found in lighter, faster bikes.

The 0‐Cross or radial pattern is built to maximise speed. The spokes go straight from the rim to the hub without crossing. These spokes are shorter, lighter and offers less wind resistance.

Why Do Bikes Have Spokes Instead of Solid Wheels?

Spokes make wheels cheap, very lightweight and strong. Coming up with a light and strong solid wheel would require expensive materials such as carbon fiber. Even then, they are still noticeably heavier.

Solid carbon fiber wheels are not unheard of, but for most regular bikes, this is an impractical option.

For example, spokes are more maneuverable because they are lighter and are not as affected by crosswinds. Bicycles are designed to efficiently make use of the strength from your legs to propel the bike forward. To illustrate, imagine the drag when biking with a solid wheel against strong crosswinds.

A good fraction of the force used would be utilized in countering the angled wind instead of moving the bike, not to mention the possibility of the bike being swept and blown around.

In sports, athletes have been known to use streamlined carbon fiber discs in velodromes — indoor track cycling arenas — for increased speed, usually combining a spoked front wheel and a solid rear disc for better maneuverability.

Discs are more aerodynamic and don’t encounter air resistance the same way spokes do.

But track cycling in an indoor arena protected from the wind is a far cry from cycling outdoors where crosswinds will make controlling the bike nearly impossible. That’s why discs aren’t normally seen in road or mountain bikes.

Summary

Now that you know how important spokes are, the next time you imagine a bicycle, you can add a bit of sparkle to the spokes in recognition of these unsung heroes.

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