Aerodynamics has been the buzz topic in road cycling for the better part of the past decade. Almost every new frame, wheel, helmet, or aero jersey is touted as being X watts faster or so many seconds quicker. But those aero claims are hard to quantify and measure in the real world. Unlike weight, there is no simple way to measure how much more or less aero one bike is versus another. Until now?
Aero Sensor, a new player in the aero measurement device sector, was almost hidden away between a wooden bike manufacturer and a stall showcasing an eBike Conversion Kit in Eurobike’s start-up zone. The British-based company has not only developed a new aero-meter, but a triplet of devices it claims to be the first “complete aero performance optimisation system.” The Aerodynamic Cycling System consists of an “Aerosensor” aero-probe up front, the “Aerobody”, an optical body position sensor mounted to the stem, and the Aerodrome, a highly precise lap timing device with sub-millisecond accuracy.
Aerosensor was founded by Dr Barney Garrood, a former Ferrari and Mercedes F1 aerodynamicist and a keen cyclist. What began as a curiosity to use his F1 expertise to assess his cycling drag quickly escalated into a career change and four years of research. Those four years have led to a development process with over 180 design iterations and an end goal of developing a device/s to bridge the gap between wind tunnel and velodrome testing, outdoor field-testing, training, and racing.
Aerosensor by name, aero sensor by nature
Several brands have brought so-called aero-meters to market over the past years. While each has its pros and cons, one thing they have in common is their complexity, with most requiring considerable patience to achieve any meaningful result. Aerosensor is hoping to finally tackle the main difficulties of at-home aero testing head-on by offering a much more user-friendly system with greater accuracy and repeatability.
The Aerosensor is a portable cycling-specific aerodynamic drag measurement device at the core of the Aerosensor system. While many will be familiar with pitot tubes found on aeroplanes, F1 cars, and some other cycling aero-meters, Aerosensor developed its own aero probe to accurately measure wind yaw angles across a range from + to – 50°.
With the slower speeds in cycling compared to F1, wind and wind yaw angles have a much more significant impact on any aero testing and measurement devices. Garrood explained that accurately measuring yaw angles is crucial in collecting reliable and valuable aerodynamic data for cycling. At the heart of the brand’s claims of “unprecedented accuracy” is the Aerosensor’s almost minuscule pitot tube that can measure yaw angles, along with a proprietary algorithm and a host of other measurements.
This CFD image shows Aerosensor’s F1 probe and a 40° yaw angle. The upstream surface sees a lower pressure (blue) while the downstream surface shows a higher pressure (red). Aerosensor calculates yaw angle from this pressure differential.
While some pitot tubes rely on a three-hole probe to measure yaw, Aerosensor’s probe effectively turns the flow onto a central pitot tube. Garrood claims that the probe always gets a reliable and stable measure of total pressure. By turning the flow, the probe can calculate wind yaw angles by gathering pressure measurements on both sides of the inlet. The upstream inner surface will see a lower pressure while the downstream surface will see a higher pressure. Aerosensor uses these pressure differentials to calculate yaw angle with a combination of all three providing the sensor with the dynamic pressure (a function of air density and wind speed) reading.
With the patented aero probe at the device’s core, the Aerosensor measures air speed, air density, ambient air pressure, and wind yaw angle. The Aerosensor combines these measurements with power and speed measurements to calculate the rider’s live* CdA (aerodynamic drag coefficient) using Aerosensor’s proprietary algorithm to deliver Aerosensor’s claimed unrivalled accuracy and repeatability in “practically all wind conditions”. The Aerosensor then transmits and displays this CdA calculation on Aerosensor’s new Garmin Connect IQ app.
*While Aerosensor states both “live” and “realtime” CdA, the figure displayed is a 30-second rolling average on the road or last lap CdA on a velodrome.
Measuring wind speed is just one piece of the aero puzzle. Precisely measuring elevation changes is equally important when calculating cycling aerodynamic drag. Every cyclist instinctively knows even minor changes in gradient will greatly affect the power required at the pedals. If an aero-meter can’t accurately sense these changes in gradient, it could mistake power variations to overcome elevation changes as an increased aero drag.
Aerosensor tested and researched the latest barometric altimeters under varying conditions to account for vibrations, varying temperature, etc to find an altimeter accurate and repeatable to within +/-10cm.
All that means Aerosensor is now seeing a claimed 1% repeatability on the velodrome and 1.5% for outdoor testing on the road. Repeatability is effectively a proxy for accuracy. If rider A does ten laps with the same setup, the Aerosensor provides a result within a +/-1% window for each lap. Taken over ten laps, that repeatability comes down to 0.5%, meaning the Aerosensor should be capable of assessing even the smallest of aero tweaks, such as gloves versus no gloves or time trial visor versus no visor.
Aerosensor can’t publicly state which F1 teams it works with, but F1 expert Craig Scarborough can.
So accurate and versatile is the aero probe design, Aerosensor has now gone full circle and is supplying the probe back to F1 with two current F1 teams running an F1 specific-variation of the same aero probe technology.
The unit itself is said to be quite aero with little to no impact on overall system drag. Tested in CFD, Garrood suggests the unit has a CdA of approximately 0.0007, or around 0.2% of rider/bike drag. “That’s around 5 grams at 40kph”, Garrood explains.”However as it sits directly in front of the bike, this merely replaces the drag from the bike frame it sits in front of. This means the net effect on drag should be zero or at least too small to measure experimentally.”
The prototype Aerosensor at Eurobike featured a body constructed from anodised aluminium with 3D printed side panels. The final production-ready Aerosensors will be available in both an injection moulded plastic casing or the same aluminium body with plastic injection moulded sides. 
The rear of the Aerosesnor has a USB-C charging port. The claimed battery life for the Aerosensor is 36 hours.
Aerobody checker, a virtual aero position coach
The Aerosensor is just one part of the new Aerodynamic Cycling System. As Garrood and the Aerosensor team developed their new aero probe design, they realised the importance of measuring body position and accurate lap time in creating a user-friendly, repeatable, and complete system.
First of those products is the Aerobody, an off-body optical point measurement system that sits on the stem and constantly measures body position. Three positional sensors within the Aerobody use infrared lasers to measure the position of the head, torso and abdomen relative to the stem with claimed millimetre accuracy.
The rider’s body accounts for the largest chunk of aero drag a cyclist must overcome. As such, body position is critically important to both on-the-road performance and repeatable testing. As riders fatigue, it becomes increasingly difficult to maintain an identical or optimal position. Garrood hopes Aerobody will help riders replicate positions from run to run in testing and offer a quick positional check during mid-competition or training rides.
The Aerobody pairs with Aerosensor’s dedicated Garmin Connect IQ app to instantly notify the rider if they deviate from their saved baseline position. The IQ app displays the current position and highlights the Garmin data field in white if the rider is in the saved baseline position, red if they have moved above the baseline position, or blue if they have dropped below the baseline. This is said to help riders maintain the same position from run to run for greater component and accessory testing repeatability like a virtual coach built into the head unit.
Furthermore, the Connect IQ app records rider body position data throughout the ride to a FIT file for post-ride comparison with aerodynamic drag data. The Aerobody can also provide riders and coaches with data to determine how well the rider can maintain their optimised time trial position in a real-world, high-intensity environment.
Aerodrome timing
Last but not least in the Aerodynamic Cycling System is the Aerodrome, a wireless lap trigger offering sub-millisecond timing direct to the rider’s head unit. Aerodrome uses a tape switch to transmit the end of each lap directly to the Aerosensor, providing the proprietary algorithm with the accurate timing required to significantly improve aerodynamic measurement accuracy in the velodrome and on the road.
By providing the Aerosensor with sub-millisecond lap data, the Aerodrome makes it possible for the Connect IQ app to display and record lap times and lap CdA results almost instantly. Riders can view live, current lap average CdA, and last lap average CdA while riding for immediate comparisons. This removes the need to stop and analyse data between tests.
If Aerosensor’s claims are true, theoretically, riders could use velodrome and field-testing time much more efficiently and potentially test more positions or equipment adaptions in less time. Seemingly a rider could test multiple hand positions, for example, across several laps and instantly analyse if one position was faster or slower without stopping or any lengthy analysing.
Furthermore, with timing information transmitted wirelessly to the Aerosensor, the system can synchronise track position with its internal calculations, making it possible to extrapolate CdA for any given part of the lap. In a velodrome, riders could compare their CdA values on the banking to the straights.
The Aerodrome is also suitable for outdoor testing and can help circumvent the elevation measurement challenge mentioned earlier. The Aerodrome allows the user to accurately set lap start and end points on either loop or out and back courses and take an average of the elevation changes recorded to correct the ride data. Garrood suggests using this method for calculating elevation change provides “an order of magnitude improvement in repeatability and accuracy.”
Be your own aerodynamicist
Aerodynamic position analysis seems like just the tip of the iceberg in terms of potential use cases for the Aerodynamic Cycling System. On a fundamental level, Aerosensor should offer riders and teams a chance to analyse and optimise their aerodynamic setups and bike positions.
Additionally, Garrood suggests that, given time, he can see riders and teams opting to run the Aerosensor system almost daily to improve their understanding of a rider’s aero drag in various conditions and compare how that correlates to what they think the drag is.
The Connect IQ app also offers riders running both the Aerosensor and Aerobody a measurement of their percentage power lost to overcome aerodynamic drag. Garrood explains this measurement will help riders understand just how much of their power output is going into overcoming aerodynamic drag across varying terrain and real-world wind conditions. This percentage on a display could help riders better evaluate whether to sacrifice power and maintain a slippery aero position or vice versa on rolling time trial courses.
Bigger picture, Aerosensor is promising more than just the option to measure aerodynamic drag on the road, but also touting the ability to correlate aerodynamic drag with what the wind is doing on a particular course on race day. You might recognise the Aerosensor from a CyclingTips report during the 2021 Tour de France looking at how an F1 aero probe helped Jumbo-Visma dominate the time trials in last year’s race. Back then, Jumbo-Visma used the same aero probe but under the Velosense name.
Jonas Vingegaard rode his time trial recon with this Velosense aero probe attached to his Cervelo P5.
The probe used in Aerosensor was developed by both Garrood and John Buckley during their time working together under that Velosense umbrella. Both have since gone their separate ways but still share the same aero probe design and patent with Buckley, now of Streamlines Aero, set to launch a similar aero sensor and body position tool package in the near future.
As we reported last year, the Velosense probe offered Jumbo-Visma the opportunity to map the wind conditions on a course on any given day. An on-course weather station might suggest an average wind speed and direction for that specific area and usually from a height much greater than a cyclist on a bike. Garrood suggests the actual range of wind speeds and directions on the course can differ greatly from point to point and at the rider’s actual height, fluctuating as much as +/-20° in oscillating wind conditions.
In recording with the Velosense on the pre-stage recon ride, Jumbo-Visma were combining the rider and course-specific wind conditions on the day of the stage five time trial with wind tunnel and previous testing data on wheels and components. From there, Jumbo was able to determine the fastest setup for that specific stage based on race day conditions.
Take wheels, for example. Rightly or wrongly, most of us currently assume deeper or aero-optimised wheels will always offer an aero improvement regardless of conditions. By contrast, Jumbo and Velosense’s approach is almost a step change in how we currently think of aero wheels. Garrood suggests there’s a range of optimal yaw angles for every wheel. If true, this could mean a wheel that might be fastest across one range of yaw angles, could stall dramatically outside that window, and actually, shallower wheels might be faster on a stage with those given yaw angles.
Furthermore, although so-called “aero-meters” are banned in UCI races, we believe, Garrood confirms teams could theoretically mount an Aerosensor to a team car to analyse mid-race conditions, which is especially useful for later starters on time trial stages.
Moving back indoors, trade, national and Olympic track teams could delve much deeper into the aerodynamic optimisation of their team pursuit and team sprint teams. The combination of the Aerosensor, Aerodrome lap timer, and the system’s ability to map the track could help teams extrapolate the aerodynamic demands on a rider at various positions within the team line and across a range of locations on the track.
Garrood also suggests the Aerosensor system could help us become more efficient with costly aero testing. During his F1 days, Garood developed new wind tunnel technology capable of giving F1 teams immediate pre-analysis feedback on wind tunnel tests. Where previously teams had to run a series of tests, stop, analyse, decide on the next steps, and then retest; Garrood’s technology made it possible for teams to instantly assess if a part or adaption was worth pursuing or if they should stop the run and move on to the next test, saving both time and money.
Garrood suggests the rate of return and resulting performance improvements correlate almost perfectly with time spent aero testing. “The more iterations you can try, the more likely you are to find improvements”, Garrood explains. “So if you can do double the tests in the same amount of time, you greatly improve your chances and simultaneous cut costs”. These testing efficiency improvements Garrood suggests could be game-changing for riders, teams, aero consultants, and anyone who relies on aero testing.
Speculating much further into the future, if Aerosensor’s accuracy and user-friendly setup prove true and pro teams have riders regularly using the Aerosensor, the data collected could go back into frame and equipment development based on real-world conditions. Somewhat similar to what Reserve has done with its three-wheeled scooter in developing the new 52/63 wheelset.
Chung-ing it
We put it to Garrood that many riders can already test their CdA using the now famous “Chung method” free of charge and perhaps with remarkable accuracy, Garrood agrees and then again points out that Aerosensor is about much more than just CdA testing.
In addition to all the potential use cases mentioned above, Garrood believes Aerosensor is still bringing considerable value even to “simple” CdA testing. Garrood suggests the Aerodynamic Cycling System adds value not in the relatively simple calculations but in accurately and repeatably matching up the power, elevation, and speed sensor data, with your position on the lap, the lap trigger, and body position. And then extracting meaningful and useful data using the Aerosensor algorithm and displaying all that on the Aerosensor Connect IQ app within seconds.
“Aerodynamic testing in the velodrome with no wind or elevation change is a pretty simple calculation. Where it gets difficult is matching up different data streams, how to account for the lean angle in the corners which changes the centre of mass position, in delivering the data to the user on a repeatable basis, etc.”
F1 learning from cycling
That aero sensor up front looks pretty familiar to what I saw during my trip to Eurobike.
Sounds good so far, but can aero testing ever really be straightforward? Unfortunately, despite the Aerodynamic Cycling System’s claimed strengths, aero testing will likely test patience as much as CdA for a while yet. Despite Aerosensor’s claimed accuracy and repeatability improvements, aero testing and aero-meters, in general, will always rely on the quality and accuracy of the power and speed data provided and the tester’s attention to detail.
While we haven’t had an opportunity to try the Aerosensor for ourselves, Garrood’s system might only improve the aero testing experience for the patient. So while we won’t get our hopes up for easy, hassle-free, aero-testing just yet, Aerosensor’s F1 links might give us hope on the accuracy front.
Throughout our conversations, Garrood was keen to stress the importance of the F1 link, but not for the usual reasons. While we often hear of technology and expertise trickling down from F1, Garrood was excited to explain how the Aerosensor technology is an example of cycling expertise flowing back to F1.
His excitement is understandable given that Garrood walked away from the no-expense-spared world of F1 expertise to develop a cycling-specific pitot tube to meet the slower speed, greater wind effect, size and weight-critical demands of cycling, only to come full circle and sell the Aerosensor technology to F1 teams.
Aero probes are now getting so small, at least partly thanks to Aerosensor’s work, teams can now mount 30 or more of these sensors on rakes to map the airflow behind specific parts of the car and wheels.
Aero doesn’t come cheap
F1 to cycling or vice versa, you have probably guessed by now that the Aerodynamic Cycling System will not come cheap. While pricing is a little complicated depending on the exact package, a quick glance will tell you the complete Aerodynamic Cycling System with the injection moulded plastic Aerosensor will set you back £1,125 (International pricing TBC). The good news is the same package with an anodised aluminium version of Aerosensor comes in at a slightly lower price of £900 RRP. In better news, Aerosensor will offer a limited number of Aerodynamic Cycling Systems via an IndieGoGo launch campaign, dropping the price to £844 and £650, respectively for the complete systems.
Furthermore, the Aerosensor (£750 / £563 on IndieGoGo) and Aerobody ( £250 / £188) are available and work independently of each other. Additionally, the Aerosensor and Aerobody will be available as a duo package priced at £950 / £713. However, the Aerodrome requires a paired Aerosensor device and is only available as part of the complete system.
Lastly, Garrood will also offer a testing device and service package which includes all three devices plus an hour-long testing session with the Aerosensor team at the Velodrome in Derby for £1,215.
More information is available at Aerosensor.tech.
