In the modern cycling world, everyone’s “getting aero”.
A huge chunk of new cycling tech and discourse is about optimizing our bikes, accessories, and our position on the bike in order to minimize aerodynamic drag, in pursuit of saving some precious watts.
In addition, the impact of aerodynamics on tactics in professional cycling cannot be understated, with a significant amount of rider behavior in big races attributed to minimizing drag.
But what is drag? And how much difference does aerodynamics actually make?
In this article, we’ll give you the complete lowdown on getting aero. We’ll be covering:
- What Is Drag In Cycling?
- How Much Difference Does Aerodynamics Make To Performance?
- How To “Get Aero”
- How Does Aerodynamics Affect Cycling Tactics?
Let’s get going!
What is drag in cycling?
Drag refers to the resistive force to motion caused by the air.
But how does this happen?
When you cycle with no wind, you’re moving at a constant speed relative to the air. You’re basically cycling straight into the air molecules, causing them to hit you and bounce off, or move around you.
This creates two distinct resistive forces to your motion: pressure drag and skin friction drag.
For a cyclist, this is likely the dominant form of drag.
Let’s consider a cyclist riding into still air. As their body, face, and bike impact the air molecules, each individual molecule exerts a force on the frontal area of the cyclist-bicycle system.
Of course, each of these forces is minute. However, when you add up the contributions from every particle, this is not insignificant at all. This results in higher air pressure in front of the frontal surface of the rider, since the force per area is higher.
The molecules also move around the rider and bike, slowing them down and resulting in fewer particles per area behind the rider. This results in an area of lower pressure.
Therefore, pressure drag happens when there is a difference in pressure in front and behind the cyclist. This pressure difference creates a resultant resistant force on the cyclist, acting in the opposite direction to their motion, known as pressure drag.
Pressure drag can be reduced in three ways: reducing the frontal area to the air, reducing the velocity of the rider, and creating a bike with specific shapes to optimize the flow of air around the bike, ensuring that the molecules are not significantly slowed as they pass around it.
Skin Friction Drag
As the molecules move around the rider, they slide along the surface. This sliding action generates a frictional force that acts parallel to the sides of the rider – i.e., opposing the direction of motion.
Skin friction drag can be minimized by changing the material from which the bike is made, along with the form of the surface. For example, this is why cyclists wear lycra: to minimize the skin friction drag. It’s also why golf balls have dimples.
How Much Difference does aerodynamics make to cycling performance?
The aerodynamics of an object refers to the manner in which air flows around it, and its potential resistance to skin friction and pressure drag.
Essentially, drag is a cyclist’s worst enemy.
At speeds as low as 15 km/h (9 mph), drag is already the dominant resistant force to a rider’s motion. At speeds above 40 km/h (25 mph), the proportion of your resistance that is due to drag rises to 90%.
Even at 20 km/h, over half of your power is dedicated to overcoming the aerodynamic drag. That’s a lot of watts that can be saved!
This is why we have seen such a shift in design philosophy with bicycles: everyone’s prioritizing the aerodynamics of a bike now.
Even in the case of lightweight climbing bikes, we have seen a shift to increasing their aerodynamic qualities. The gains that they offer, in general, are just far greater than decreasing the weight or altering the mechanisms of a bike.
How to “get aero”
So clearly, reducing your drag is extremely important as a cyclist. But how do you actually do it?
Getting aero is essentially made up of two components: reducing the aerodynamic drag of your bike, and reducing the aerodynamic drag of yourself, as the rider.
Getting Aero: What do aerodynamic bikes look like?
Aero road bikes are made with one thing in mind: minimizing drag.
An aerodynamic road bike will usually be made of carbon fiber. Part of the reason for this is that carbon fiber is far easier to shape than other materials such as aluminum and steel, which have to be drawn out into tubes.
In order to minimize pressure drag, an aerodynamic road bike will be as thin as possible, reducing its frontal area.
The tubes will also often take the shape of an aerofoil (an airplane wing), in order to reduce the amount that the air molecules are slowed down by as they move along the surface of the bike, resulting in a smaller pressure difference in front and behind the bike.
In order to minimize skin friction drag, aero road bikes will often be textured – on a microscale – in such a way that they have less surface to exert friction on the air (in the same way that a golf ball has dimples, but to a lesser extent).
Aero road bikes are so efficient at decreasing the pressure drag that the dominant resistive force is actually skin friction drag, in the same way as it is on an aerofoil.
Getting Aero: How to minimize the drag on yourself, the rider
The aerodynamic qualities of the rider play by far the largest role in reducing your drag on a bike.
In fact, around 80% of all drag experienced on a bike is on the rider’s body.
This is generally minimized in two ways. The first is to reduce the skin friction drag by wearing lycra, using aero shoes and helmets, and shaving your legs (though this last one is an extremely minimal difference… don’t tell the MAMILs!).
The second, and by far the most important aspect of getting aero, is reducing the pressure drag through your position on the bike.
In fact, by changing your position alone, you can increase your performance by up to 20%. That’s massive, in the context of a time trial or a race, for example.
In order to adopt an aero position on a bike, you need to minimize your frontal area. The first step here is to move your hand position from the bars or hoods to the drops. This changes your body position from largely upright to much more tucked.
You can then attempt to keep your chin as close to the bars as possible, keeping your back as straight as you can. Additionally, if you want to get really aero, then you’ll need to have your head somewhat down.
How Does Aerodynamics Affect Cycling Tactics?
A huge amount of the tactics involved in professional cycling are about aerodynamics.
The most obvious of these is drafting.
Every cyclist knows what drafting is. It’s where you sit in another rider’s “slipstream”, thereby reducing the aerodynamic drag you experience as you ride.
This works because, when the first rider moves through the air, they are subject to a pressure drag. This means that the pressure behind them will be significantly lower, which is referred to as their slipstream.
So, the pressure drag on the subsequent rider will be lower since the pressure in front of them is reduced significantly. In fact, through drafting on only a single rider, you can reduce your aerodynamic drag by 50%.
Drafting at the back of a peloton results in even more significant gains, with reductions in drag of up to 94%!
We see this all the time in professional cycling, whereby a GC contender will be drafting behind their domestiques, in order to save their energy. The teammates at the front will often rotate in order to keep up a high speed for the GC contender.
Another example of drafting is during the sprint finish. A sprinting lead-out is essentially a rider taking the brunt of the drag in order to allow the sprinter behind them, to conserve their energy for a powerful acceleration into their sprint.
In addition, on days with a strong crosswind, we often see cyclists form an “echelon“. This is where a team will orient themselves parallel to the wind direction, i.e. across the road, in order to shield the team leader from the worst of the powerful crosswind.
A major context in which we see aerodynamics affecting cycling equipment is during a time trial.
Here, riders often use a dedicated time-trial bike in place of a road bike in order to minimize the drag on the bicycle.
These are extremely aero road bikes, often making use of a disc wheel (which reduces skin friction on the wheel), and aero bars that allow for the “puppy paws” position to be adopted legally and safely.
Additionally, among elite cyclists, one of the major factors that separates the best time-trial cyclists from the rest is their ability to adopt and hold extremely aerodynamic positions, something that has a huge effect on their performance.
So, should you be getting aero?
If you want to get faster: yes!
A massive amount of modern cycling is to do with aerodynamics, and the pursuit of getting aero is never-ending. The possible gains are massive, with technology constantly improving to allow for drag to be reduced even further.
So, no matter how serious a cyclist you are, it’s worth getting aero! Your rides will be faster with the same amount of effort. Who doesn’t want that?