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.  

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 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 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.  

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.

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.

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.

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.

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.  

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