posted by George Cant
July 13, 2015

Finally unveiled! The Swiss Side Instrumented Bike Project.
Using technologies direct from Formula 1 motorsport, combined with CFD, Wind Tunnel and Performance Simulation methods performed at a level unequalled in the cycling industry, Swiss Side finally releases the complete details of their Instrumented Bike Project. This unique system, developed by the team’s engineers with over 50 years combined F1 experience, features an array of sensors on a time trial bike for measuring and characterizing the aerodynamics of the bike and rider system. The Instrumented Bike is the fourth corner stone in Swiss Side’s arsenal of highly evolved aerodynamic development tools. Its purpose is to answer fundamental questions, key to aerodynamic development and the project has been conducted together with Swiss Side pro-triathletes, the Raelert Brothers, as well as a selection of athletes from all levels.


1. Aerodynamic Drag is the single most important performance parameter in cycling
2. Better understanding = Better products = Better performance

Swiss Side’s goal is to produce the best-engineered products, offering the ultimate in ‘real world performance’, measurable out on the road where it matters. In order to achieve this, a true understanding of the ‘real world’ is required. This includes not only understanding the onset wind conditions which a cyclist encounters on the road, but also how this affects the rider and the impact on overall performance. Different athletes react differently, so data is collected from a broad spectrum of riders from the pro-level to the hobby athlete.
The data collected from the Instrumented Bike sensor system offers a level of understanding about real world cycling aerodynamics, which currently does not exist. This understanding allows a better definition of the performance measures used for rating the aerodynamic performance of a particular product. For example, the effective ‘weighting systems’ used in CFD & wind tunnel testing, for calculating the relative importance of the performance parameters (eg. drag, side force, steering moment, overall bike moment) at each yaw angle, can be more realistically defined. The end result is better performing products out on the road, not just on a graph.


Capturing an accurate picture of air speed and cross-wind angles which a rider encounters on the road is very important for defining the weighting systems for the performance parameters measured in CFD and wind tunnel testing.
There have been previous attempts to capture the air speed and angle using wind anemometers mounted to the tri-bars, however, there are two fundamental flaws with this approach:
1. The presence of the rider and the resultant backpressure has a significant influence on both the air speed and angle measurement, making them inaccurate.
2. Theses devices also require the physical movement of parts for the measurement. The mass of these parts makes them incapable of accurately capturing sudden wind gusts, which are actually the most important events affecting the rider.
In order to overcome these issues, air probes more common to aircraft and the front of Formula-1 cars were designed and positioned as far forward as possible, out of the influence of the rider and bike. These are coupled to highly sensitive sensors capable of accurately capturing the air speed and angle at frequencies of 20 times per second.
The lower probe is the pitot-static air speed measurement probe.
The upper probe is the yaw (cross-wind angle) measurement probe.

This static pressure plot shows the air probes heads have been placed in the least influenced region ahead of the bike and rider.
The rider accounts for up to 80% of the drag of the bike-rider system. For this reason, the rider position is extremely important to overall performance. Therefore it very important to track the rider position and height.
Sensors capable of measuring both position and load (weight) are positioned in key positions of the bike- on each side of the handlebar, on each tri-bar elbow-pad, and on the seat. An additional sensor is attached between the bike frame and the neck of the rider, allowing the height of the rider’s body to be monitored.
With this array of sensors, it’s possible to track the position and height of the rider at any point in time in the data.
An event button in positioned on the tri-bar adjacent to the cycle computer. In the case of a particular event of interest, such as a sudden wind gust, the rider can effectively ‘mark’ this point in the data by pressing the sensor. With the use of all other sensors and the on-board camera, it is then easy to analyse this event in the data post-processing phase.
The angle of the front wheel and the steering torque (turning force) is very important for tracking the steering sensitivity of the front wheel. Particularly when wind gusts occur, or in high-speed descents, the sensitivity of the front wheel is very important for the rider. If the front wheel responds unpredictably, or with a large torque, then the rider feels unsteady and tends to either reduce power or to lift the body out of the aero position to counterbalance, both of which result in significant performance losses. Therefore monitoring how the rider reacts in such situations, and the threshold of sensitivity for the rider, is fundamental for the choice of front wheel profile depth on windy days, as well as for the development of the front end of the bicycle.

Monitoring the angle of the bike (roll) particularly in cross-wind conditions is important for understanding the limits for the rider. For example, a certain intensity of cross-wind requires the rider to lean against the wind with an angle. Once a certain angle is exceeded, the rider cannot maintain a consistent power output, which can result in significant performance loss. In such cases, a lower profile wheel set and/or a bicycle frame which generates less side force, can actually bring overall performance gains.
The bike angle sensor pitch function is only important for tracking when the rider is going over the handlebars, or doing a wheelie. In both cases, performance losses are pretty major!
An SRM Power Meter, custom built by SRM for this project to provide higher accuracy rider power output measurement, is built into the Instrumented Bike. Monitoring rider power is extremely important because rider power and aerodynamic drag are the same, only acting in opposite directions. So any aerodynamic event (e.g. wind gust) that causes the rider to reduce their power output, must be considered.
For example, if an athlete is riding on a windy day with 300W power output and a large cross-wind gust destabilizes them causing them to stop pedaling to catch their balance, even if they remain in their aerodynamic position, the momentary loss in power is 300W. It’s possible that the rider could maintain a more constant power output with a different setup such as a lower profile, less cross-wind sensitive wheel set. The associated drag penalty would only be the order of 3W. In this case, the overall better package on a windy day, could be be the slightly higher drag, but less wind-sensitive wheel setup.
Therefore monitoring how aerodynamics affect the rider power output is an important part of the Instrumented Bike in conjunction with the other sensor measurements.

An on-board camera system is installed to monitor the rider. The footage from the camera is synchronized with all data measured, enabling the engineers to visually analyse and understand any particular events of interest in the data. For example, if a large wind gust is recorded, was this a real gust or a passing vehicle? Like this the data can be filtered to ensure only ‘real world’ relevant data is considered.
Typical bike computer measurements are also collected with the Instrumented Bike sensor data. If the wheel speed is lower than the air speed measured on the pitot-static probe, then the rider is in a headwind. Pedal cadence is also of interest to see if there are any aerodynamic inputs which affect the rider’s cadence, for reasons of balance for example.
The GPS data is useful not only for tracking the riding route, but it is of particular importance for mapping the aerodynamic conditions present on a particular course. Different courses have different geographical features which can influence the wind conditions and in turn the aerodynamics. Therefore, the GPS data is linked to each data sets so that trends can be compared between similar route types. E.g. windy flat coastal courses vs. hilly inland courses.
All data from the sensor system is logged and stored in an on-board data acquisition system. This is installed in a modified drinks bottle, positioned in a relatively aerodynamically neutral position. The logger is capable of storing over 12 hours of data from all the sensors. At the end of a session, the data is downloaded into Swiss Side’s in-house developed post-processing software for analysis.


The complete Instrumented Bike system was calibrated in the wind tunnel before road testing. In the controlled wind tunnel environment, accurate aerodynamic measurements are made so that the real word data collected out on the road can be matched to accurate wind tunnel data. For example, the aerodynamic drag associated with a range of rider positions was measured, so that the true performance gains/losses of the rider movement measured on the instrumented bike out on the road can be quantified.

The Instrumented Bike during wind tunnel calibration.

Wind tunnel measurements with Andreas Raelert on the Instrumented Bike system.

Following the extensive development phase and subsequent calibration of the Instrumented Bike, ‘real world’ road riding measurements were conducted. Data was collected with Swiss Side pro-triathlete Andreas Raelert in order to better understand his riding style and consequently to allow better optimization of his aerodynamic setup. Subsequently, the Instrumented Bike has been used for data collection with a range of riders, in mountainous as well as coastal regions, wind-still as well as windy areas, and with different riders with varying riding styles.

Swiss Side Pro-Triathlete Andreas Raelert on the Instrumented Bike.


The data collected on the Instrumented Bike is processed in Swiss Side’s in-house developed post-processing software. With the masses of data, logged at very high frequency over hours of riding, a smart tool is required for processing and filtering the data into a useable state. A bespoke tool was developed for this purpose. The software allows the Swiss Side aerodynamics team to display and overlay data. Graphical outputs can be produced and data compared between different courses, different riders etc. In this way, the engineers can understand how the aerodynamics affect the rider in a way never before possible.

Speed plots from Swiss Side’s in-house developed IB Post-Processing software. – Some data collected riding into a headwind: yaw (cross-wind angle), air speed, wheel speed.

Yaw (cross-wind) angle frequency distribution plot from IB Post-Processing software. This gives valuable information on how often each yaw angle occurs for the development ‘weighting systems’.


The data trends and various scenarios of choice are then input into Swiss Side’s Performance Simulation toolbox. Any scenario can be simulated to estimate the time gain or loss over a particular course. Course profile, bike and rider weights, power output, rolling resistance, wind, aerodynamic drag, etc., are all parameters considered by the performance simulation tools.

Data output from Swiss Side’s in-house developed Performance Simulation software, showing predicted performance time differences across the range of Swiss Side wheel models, for the given scenario.

Like this, the Swiss Side aerodynamics team is better able to quantify the parameters contributing to ‘real world performance’ measured out on the road, on the stop watch, where it matters.

Consequently, Swiss Side develops better products from the ground up. Only with the use of the Instrumented Bike and the real world data it produces, used in conjunction with the other 3 cornerstones of the Swiss Side aerodynamic development system – CFD, Wind Tunnel and Performance Simulation, can aerodynamic development be done in the correct way. Anything else employs a degree of guesswork.
The Instrumented Bike and the complete Swiss Side Aerodynamic Development System is used not only for the development of Swiss Side products and optimizing the pro-rider setups, but also for the development of industry partners products, as part of the ‘Aerodynamics by Swiss Side’ program. Purchasing a product developed by Swiss Side, guarantees the absolute best level of aerodynamic performance.
Stay tuned… The Instrumented Bike is not the final frontier. Swiss Side is already working on the next unique and exciting project, to further the development and understanding of aerodynamics in cycling.

With 50 years of Formula 1 experience, Swiss Side strives to revolutionize cycling aerodynamics to maximize the performance of affordable aero wheels. Top quality, unbeatable aero wheels delivering maximum “real world performance” at an affordable price.
For more information:, and @swissside.