Streamlines: REAL WORLD AERO TESTING(VIDEO)

CdA—three letters that underpin nearly every conversation in time trial and long-course triathlon racing. Short for coefficient of drag area, CdA quantifies how much aerodynamic resistance a rider presents. In simple terms, the lower your CdA, the less power you need to hold speed. It’s one of the most decisive metrics in race performance.

Three Ways to Measure CdA

There are three primary methods athletes use to test and refine their CdA:

1. Wind Tunnel Testing

The most technically sophisticated—and cost-intensive—option. Wind tunnels allow testing the largest number of variables across a range of yaw angles and wind speeds. They’re ideal for benchmarking how specific equipment performs in different wind speed and wind angle conditions.

But there’s a caveat: riders often adopt positions they can’t realistically sustain in race conditions. This is especially true for long-distance triathletes chasing small gains. Because the rider remains static, fatigue isn’t a factor—unlike race day. It’s easy to walk away with a flattering CdA value that doesn’t translate outside the tunnel. Nonetheless, it’s a powerful tool when used with positional honesty and clear test objectives.

2. Track Aero Testing

Track testing offers a controlled environment while still requiring real-world handling and position stability. Measurement systems take a rider's power and speed, combined with atmospheric conditions, to calculate CdA. Once familiar with the rhythm of the velodrome, riders can focus purely on the run—no distractions, just data. While consistent and repeatable, it does require booking time at an appropriate facilit,y and simply riding on a velodrome comes with a learning curve for newer riders.

3. In-Field Aero Testing

Field-based aero testing is becoming the most accessible and race-relevant method for many athletes. Using on-bike sensors (wind and body position sensors), the power meter, and speed sensor, field testing allows you to assess aerodynamic performance in the conditions you’ll actually compete in—wind, gradient, temperature, and surface variability included.

Like track aero testing, there is hardware and software required, but with more freedom for locations. The fact that it is outdoors, does inherently limits some locations in some months of the year.

Streamlines Brief Background

Streamlines is the new kid on the block, well, sort of. The foundations of the hardware that comprises the system started to take shape in 2016. It was 2021 when the Streamlines ecosystem really started to evolve, for real-world aerodynamic measurement, and their devices started to emerge with the (then) Jumbo-Visma team.

Since then, John and the team from Streamlines have not been standing still. They have now amassed World Tour teams and Pro Teams to adopt the use of their technology, and to no surprise.

Streamlines has developed the hardware and software that allow for accurate and reliable in-field measurement of aerodynamic efficiency. Combined with an accurate power meter and a speed sensor, Streamlines provides the equipment and protocol for actionable aero insights—outdoors, under real-world demands. The Streamlines system is one of the most valued developmental tools we use here at Sync.

Take a look at our new YouTube video to see how the session went.

Field Testing with Streamlines Aero

We partnered with Streamlines for our latest sessions to conduct in-field testing using the CIRRUS ecosystem. The Wind and Body devices attach directly to the bike and body position dynamically, while you ride. Speed, power, wind, environmental, and body data are all transmitted and logged in the NIMBUS data logger. The Android phone doubles as the data logger, sending the ride file to the cloud the moment the run is completed, for automatic processing in the online portal.

Where traditional field testing requires a lot of manual input and post-processing to get an estimate of CdA, the Streamlines ecosystem closes the loop and automates the process. This maximises time and enables truly actionable feedback.

With Dylan and Martin, we tested various configurations—hydration, helmets, and clothing—while riding at target race intensities. The result? We gained clarity not just on what was fast, but on what each athlete should focus on for maximum benefit.

The CIRRUS system allows cyclists, coaches, and manufacturers to test their aerodynamics quickly and precisely. Unlike wind tunnels, CIRRUS allows for real-world testing, eliminating the need for travel and expensive hourly rates.

Findings

For Martin, the main objective of the test was water bottle positions. With the ability to now hold two 1-L bottles behind the saddle, we tested every option possible. The findings were positive in the sense that there seemed not to be a penalty for bottles behind the saddle with this specific setup.

"We are happy with the initial work done in aero testing on the velodrome. We now want a more realistic picture of aero performance in the field. We are working through bottle placement and the development of accessories to support both aero performance and hydration requirements, and the Streamlines CIRRUS system can give us immediate, valuable feedback."-Ken Ballhause

”It was very interesting to cross reference the data from the velo to the real road. I think field testing is the real thing to be honest. In the velo a could get a crazy tuck going and not really have to look up where as in the road it felt more realistic with looking up the road, dodging rough patches, etc. It was also good to have data on the penalties of bottle placement. Personally I want to relay as little as possible on the aid stations on course, so knowing I can carry a lot with out it solwing me down is a good thing to know. Overal I was very happy with the field testing, I think this will be my preferred method of testing moving forward” -Martin Ulloa

Dylan found that the helmet played a huge role when playing with different fabrics on the sleeves. To the point where it became clear the helmet choice should be the first part of the puzzle when looking at upgrades on top of a good position. 

"Dylan is playing an important role in assisting with some equipment testing, benchmarking a number of road cycling helmets, as well as time trial garment configurations. For this, we have set Dylan up on the new Giant Trinity."-Ken Ballhause

"Aero testing out in Doreen was a really successful day. I trialed different helmet, sock, and overshoe combinations and uncovered performance gains I wouldn’t have otherwise found. The standout result was the integration of the Rudy Project helmet into my position. Its wide, flared shape helps smooth airflow across the top of my head and shoulders, reducing turbulence and improving efficiency."-Dylan Procker-Parker

The CIRRUS aerodynamic drag measurement system is a comprehensive ecosystem of hardware and software that streamlines the entire testing process—from setup and data collection to analysis. As Ken Ballhause explains, it’s unlike any other aero testing solution.

"At Sync, we leverage the CIRRUS system to evaluate athlete performance, optimize time trial positions, and refine equipment choices—from cockpit setup and garment selection to helmet placement, much like positioning bottles in triathlon. The system also plays a key role in the ongoing development of our products, such as the evolution of the Sync AB03 and its accessories. Ultimately, testing with CIRRUS helps us validate our designs and generate innovative ideas for future advancements."-Ken Ballhause

Understanding and optimizing aerodynamic performance is crucial in the world of time trial and long-course triathlon racing. Whether through traditional wind tunnel testing, track aero assessments, or the increasingly accessible field testing methods like those enabled by Streamlines and CIRRUS, athletes and teams are continually pushing the boundaries of what’s possible. The integration of advanced tools and real-world data not only provides immediate, actionable insights but also accelerates innovation in equipment and positioning. With technology advancing rapidly, the future of aerodynamic optimization is more precise and accessible than ever—making every watt and every gain count.