Understanding Being Aero & Watts For Cyclists

We commonly hear the phrase “be aero” in the cycling world, but what does it really mean? The quick answer, “being aero” is when the watts you put into the pedals are used to move you forward and not used to overcome drag, therefore making you faster.

We already know that being aero is important. Most cyclists would agree. But would you know how to answer the question, “why is aerodynamics important and what does being aero help accomplish?” If you don't know, that’s okay (that’s the point of this article) and if you do, read on, there still may be something new to learn. Aerodynamics is difficult to visualize and requires complex and expensive testing equipment to measure, like a wind tunnel. This article will help you visualize aerodynamics, understand why “being aero” matters, and suggest the best ways to become more aero. Let’s get started.  

What Is Drag?

Drag is a force acting opposite to the relative motion of an object moving through a surrounding fluid. Let’s break it down piece by piece.  

Fluid

Fluid is either a liquid or a gas. Most people think of fluids as something like water, but the air we breathe is also a fluid in a different state.

Relative Motion

Relative motion through a fluid refers to how quickly we are moving through the fluid, while also taking the motion of the fluid into consideration. Speed is most commonly referred to as our speed relative to earth, which we consider to be zero. Picture being in a canoe moving along the shore of a lake. If the canoe is moving at 5mph, the canoe is said to have a speed of 5mph. If the water in the lake is still, then we are moving through the fluid at 5mph. If, however, we moved our canoe to a river, we could a.) let the river take us down stream and not paddle. In this case, our relative velocity is zero because our speed relative to the shore is 5mph but our speed in the water (the fluid) is actually the same as the speed of the moving water.

Or, b.) we could paddle up stream at 5mph opposite the water moving downstream at 5mph. In this scenario, our canoe moving through the water has a relative velocity of 10mph -- 5mph down + 5mph up -- but our speed relative to the shore is only 5mph.  

Force Acting Opposite The Relative Motion

The force that acts opposite the relative motion can also be visualized by a river. Imagine getting out of your canoe and into the rushing water. If you pick up your feet and allow the water/fluid to move you, you are not doing any work and no drag force is applied. If you decide to stand or walk up river, against the current, your body is opposing the motion of the fluid and the force you feel going against your body is drag force.

This feeling of drag in liquid fluids is more severe than drag through gaseous fluids. The drag you experience on the bike when riding is the same as if you are in the river. You can feel the opposing force riding into a head wind or if you’re riding with a strong enough tail wind, you can do nothing and ride along without any opposition from the gaseous fluid, or air.

Aerodynamics & Watts

For all intents and purposes, pedaling is required to move forward on a bike. (Yes, the bike can move forward if you’re in a crazy tail wind, but in general, pedaling is required.) We measure the energy from our legs that moves the bike in watts. Ideally, every watt you put into the pedal is used to move you forward, but there are some losses along the way. One of those being the need to overcome the drag you experience moving through the air. So, to answer the earlier question, “being aero” means you are using more watts to move you forward rather than wasting them overcoming drag.

Common Ways To Overcome Drag

Your Fit

The largest component of drag on the bike is your body, which accounts for roughly 80% of the total drag. A great bike fit is extremely beneficial and will help you find your most aerodynamic position to lower the drag percentage. Your goal is to find a position that allows you to be aero and have the ability to maximize your power output. You do not want to be able to hold the position for less than 10 minutes or not be able to pedal efficiently. A good fitter will understand your needs. For more on bike fit, listen to Episode 17 of the FASTER podcast and hear what expert bike fitter, Jim Manton, has to say.

Your Bike

An aerodynamically optimized bike provides a real advantage. Nick Salazar from TriRig talks about the right equipment, including bike frames in Episode 32 of the FASTER Podcast.

Your Wheels

If you already have a great bike and a good fit, the most advantageous upgrade you can make are your wheels. Aero wheels allow the air to move around the wheel more smoothly, reducing the drag. All of our wheels at FLO are aerodynamically optimized using our optimization algorithm that was developed after analyzing data collected from on road testing. You can read more from that journey here.

Your Helmet

An aero helmet is another way to become more aero. We’ve learned that helmets are personal, meaning a particular model may work well for one person, but may not work well for another. Testing, if you can, is a great idea.  

Your Kit

A tight fitting and properly placed kit seems to help reduce aerodynamic drag.

General Ideas

When trying to optimize yourself for aerodynamics, it’s important to look at the small things. For example, where do you put your race number? Do you attach it to the front of your bike or have it flapping off your kit? Instead, try having it securely attached and out of the way of airflow.

Keep cables concealed or tight to the frame, choose tires that are optimized for your wheels, check your bottle placement, etc. In episode 12 on the FASTER podcast, Ryan Cooper touches on many of these factors and their aero benefits.

If you still want to learn more, other FASTER podcast episodes that talk about aerodynamics are Episode 24 with Tom Anhalt and Episode 35 with Andrew Buckrell.

Final Thoughts

Hopefully, this article allowed you to see how aerodynamics matter and ways to “be aero” so you can get the most out of your watts.

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