THE SCIENCE BEHIND SPEED


Aerodynamics: Why carbon wheels make all the difference

Cycling isn't just about strength and endurance; it's also about cleverly managing resistance. Everyone knows the feeling of a headwind, and aerodynamics determine how much energy you need to maintain speed. At Autumn Wheels, we believe wheels play a crucial role in this battle against air resistance. That's why we explain why switching from aluminum to carbon fiber is a logical step, and how rim and tire width work together.

From aluminum to carbon

Aluminum wheels have been the standard for years: strong and reliable, but often heavy and less aerodynamic. Carbon has changed that.

At Autumn Wheels, we use Japanese Torayca™ carbon fibers – recognized worldwide as the highest quality for high-performance wheels. The production process begins with the synthetic polymer polyacrylonitrile (PAN). This polymer is polymerized into long chains, which are then spun into thin fibers. The fibers are then stretched, aligning the molecules lengthwise. This step largely determines the tensile strength and stiffness of the final fiber.

The fibers then undergo a stabilization process, where they are slowly heated to 200–300°C. Carbonization follows, where the fibers are heated to 1000–2000°C in an oxygen-free environment, resulting in nearly pure carbon. For added stiffness, this can be increased to 2500–3000°C. Finally, the fibers are thinly coated and processed into fabrics or unidirectional layers, ready to be made into wheels.

From carbon fiber to wheel

Once the carbon layers are ready, Autumn Wheels begins the actual wheel production process. Stacking the layers—the layup—is a crucial step. Each layer has a specific function:

  • Longitudinal layers provide maximum stiffness and direct power transfer

  • Cross-laid layers provide extra torsional stiffness and increase durability

  • Additional layers around spoke holes and hub mounting provide extra reinforcement

The layers are then placed in a precision mold and pressed under high pressure and heat in an autoclave. The resin hardens, and the layers permanently bond into a single, solid rim. The result is a wheel that is extremely light, stiff, and yet flexible in a controlled manner. This flexibility dampens road vibrations, increasing comfort and stability while riding.

Why Aerodynamics Makes You Faster

Imagine: you're cycling fast and the wind is your biggest enemy. The faster you go, the more air resistance you feel. At higher speeds, above about 40–50 km/h (25–31 mph), air resistance becomes the biggest energy consumer. That's why it's so important that wheels are cleverly designed.

Aerodynamic wheels help guide air smoothly over the bike and its wheels, reducing energy loss and allowing you to ride faster. The difference is noticeable: it feels like you're gliding through the wind instead of fighting it.

The effect of rim height in practice:

  • 30 mm → especially light and suitable for climbing, limited aero advantage

  • 50–60 mm → at speeds above 35 km/h you save 5–10 watts (~3–5%)

  • 80–90 mm → in time trials and triathlons you save 20+ watts (~6–10%)

A well-designed carbon wheel combines a high profile, light weight, and stiffness. Together, these properties ensure less drag, improved power transfer, and controlled compliance that dampens vibrations.

If you'd like, I can add a section on rim and tire width to complete the blog post and explain why we at Autumn Wheels opted for a 25mm outer rim width. That would really round it off for your readers. Would you like me to do that?

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