How Easy It Is to Cheat with Aerodynamic Data
Aerodynamics is in sharper focus in both triathlon and cycling than ever before. Manufacturers are locked in a constant battle to "save" the most watts, heading to the wind tunnel or the velodrome to prove that their specific product is the absolute best.
But behind the polished graphs and impressive figures lies a truth that rarely reaches the consumer: it is incredibly easy to manipulate the data generated in a wind tunnel.
In this blog post, we dive deep into how data can be skewed and how you can see right through the marketing smoke and mirrors. Afterwards, you can check out this follow-up post, where we showcase a real-world test of our products in the Tempo! Wind Tunnel to demonstrate why aerodynamic optimization can never be reduced to clever slogans and simple marketing buzzwords.
The Yaw Angle: Picking the Perfect Wind
The yaw angle is the first tool a manufacturer can use to make a product look better than it actually is. Yaw refers to the net angle of the wind hitting the bike and rider. In a wind tunnel, technicians can rotate the rider to simulate various yaw angles.
Some products are fastest in a direct headwind (0° yaw).
Other products excel when hit by a slight crosswind (e.g., 4°–7° yaw).
A manufacturer can easily choose to publish data only from the specific angle where their product outperforms the competition, completely ignoring the angles where it falls short. The problem is that the data you see doesn’t reflect real-world riding. On the open road, wind angles change constantly. You want a product that performs consistently well across a broad spectrum of angles, rather than one that excels at just a single, cherry-picked angle.
There is nothing wrong with testing at a specific wind angle that represents real road conditions. The issue arises when a brand intentionally highlights an unrealistic angle just to win a graph.
Testing Bikes and Wheels Without a Rider
Testing wheels or frames by themselves is a classic way to manipulate results. While testing "naked" equipment can be a highly useful tool during early product development, what matters most to you is how a wheel interacts with the bike, and how the bike interacts with the rider.
When you are out on the road, your body position accounts for roughly 80% of the total aerodynamic drag. Your arms, torso, and spinning legs drastically alter how airflow moves around the equipment. Therefore, evaluating gear without a rider in the equation is virtually meaningless. To get a true picture, equipment should be tested with actual riders of varying body compositions and sizes.
This is also why relying solely on CFD (Computational Fluid Dynamics) analysis falls short. CFD is a computer simulation of airflow. It provides incredible, essential insights, but it can never stand alone. For instance, most static CFD models cannot accurately simulate a rider's legs actively spinning. This creates massive uncertainty, as moving legs completely disrupt the airflow over the rear of the bike. Real-world wind tunnel validation is a must.
The Strawman Fallacy: Rigging the Comparison
Even in a wind tunnel, data can be manipulated. This occurs when a manufacturer intentionally selects a weak competitor baseline to make their own product look revolutionary.
The Setup: A brand launches a new mid-depth carbon wheelset.
The Trick: Instead of testing it against the market's current top-tier aero wheels, they compare it to a cheap, shallow, heavy aluminum training wheel.
The Result: The consumer is presented with an incredibly impressive bar chart showing massive watt savings.
While the numbers themselves are technically accurate, the comparison is completely disingenuous. It is not a real-world comparison between two peer products.
Speed and the Boundary Layer: The Complexity of Fabric
The same misleading results can be achieved by choosing a very specific testing speed. This is especially true for cycling apparel, where different fabrics perform wildly differently depending on how fast you are moving.
You might assume that if a jersey is aerodynamically superior at 30 km/h, it will also be superior at 50 km/h. However, the physics of fabric is far more complex, dictated by what is known as the boundary layer.
As air flows over a surface, a micro-thin layer of air forms right against the fabric. At lower speeds, this airflow is often laminar (smooth). At higher speeds, it becomes turbulent. When you wear a modern speedsuit with distinct textures or ribs on the sleeves, that texture is engineered to intentionally force the air to become turbulent.
It sounds counterintuitive, but turbulent air actually clings better to the curved surface of your arms, significantly reducing the low-pressure wake (the "suction" effect) created behind you.
This is a delicate balancing act. The exact coarseness of the fabric structure determines the speeds at which it operates efficiently. At lower speeds, aerodynamic resistance is heavily dominated by pressure drag (form drag). As your speed increases, that exact same fabric texture can become too aggressive, creating excessive skin friction (surface drag), which plays a progressively larger role at high velocities.
In simpler terms: The sleeves that slice through the wind perfectly at 30 km/h are not necessarily the ones that perform best at 60 km/h.
Navigating the "Drag Crisis"
This brings us to the drag crisis, the exact velocity point where a fabric's texture successfully triggers the transition from laminar to turbulent flow, drastically dropping the aerodynamic drag coefficient.
Depending on how a fabric is woven, this drag crisis might cover a very narrow, hyper-specific speed range, or it might be engineered to span a wider spectrum of velocities. When choosing a race kit, it is absolutely vital to choose a fabric engineered to perform at the specific speeds you actually compete at.
The Danger of Absolute Watt Claims
The final and most common trap to watch out for is when brands market test results in absolute watt savings. It is highly oversimplified and incredibly easy to manipulate.
If a manufacturer claims a flat "10-watt saving," it sounds fantastic. But without knowing the exact testing speed and rider context, that number is meaningless:
For a rider traveling at 60 km/h, a 10-watt saving represents a minor 1.42% reduction in total aerodynamic drag.
For a rider in the exact same gear traveling at 30 km/h, that same 10-watt saving would represent a 11.42% reduction in total drag.
Any watt reduction presented to you must always be evaluated in direct relation to the specific speeds and real-world scenarios you will actually encounter on your rides.
To make this completely concrete, we took our own gear into the wind tunnel and ran the numbers. You can read the full breakdown of that benchmark test right here.