FLO All Sport Series – The A2 Wind Tunnel Results

From an aerodynamic perspective, the wind tunnel is the the ultimate test of any product. When designing the FLO Gravel series we realized the importance of a wide internal-rim width when trying to lower rolling resistance. The goal with the FLO All Sport Series was to widen the internal-rim width, and optimize rim shapes around tires ranging from 25-32mm, all while producing a faster wheel than our previous models. Quick answer, we did it. Read below for all the details.

We tested the new FLO All Sport line and our existing line of wheels with Continental GP 5000 tires in 25mm, 28mm and 32mm sizes. We also compared the new FLO All Sport line to a Mavic Open Pro to show the benefits over a standard OE wheel.

For accurate results, you need a testing protocol. Small changes can have a large effect on the outcome, especially in a wind tunnel. For example, different tire pressures or different tires can change the results. Tires have different molds and each mold produces different results, so a testing protocol helps ensure these items remain consistent.  See below for our testing protocol:

1. Before testing the wheels in the wind tunnel, we run a tare run. This allows us to calculate and compensate for the drag caused by the fixture used to hold the wheels in place. This “tare value” is then removed from future tests so we have accurate aero results.
2. Then, we set tire pressures for each wheel using an Ashcroft pressure sensor. This allows us to set the pressures within 0.1% and make it repeatable. Over the years we’ve learned that removing a pump from a valve can result in a 5psi loss. We use a specially designed valve that allows us to close the valve and prevent air loss when the pump is removed.
3. Once the wheel was mounted in the wind tunnel and the fans were turned on, each wheel was swept from 0-20 degrees of yaw, in 2.5 degree increments.
4. A measurement at each yaw angle was taken twice and averaged.
5. This was repeated with the differences mentioned above, but we make sure same tires and tire direction is used for each test when comparing one wheel to another.

In 2015, we built a computer that mounted to the front of a bike we rode in multiple riding scenarios and collected over 100,000 data points. These data points taught us how a cyclist interacts with the wind when riding and what percentage of time they spend at each yaw angle.

In the wind tunnel, we measure the coefficient of drag (CdA) produced by the wheel at each yaw angle. Using this value and making the assumption that a cyclist is traveling at a relative velocity of 22mph, we calculate the number of watts the wheel produces at that yaw angle.

Since we know the average time a cyclist spends at each yaw angle and the watt value for each yaw angles, we can calculate the average watt value for any given wheel.

The results we receive at the wind tunnel are an important part to the whole development of the wheel. It gives us the aerodynamic part, but for these wheels, we also considered rolling resistance. These add up to Total Power, or a measurement of the number of watts it takes to overcome aerodynamic drag and rolling resistance. The wind tunnel tells us the number of watts consumed by aerodynamic drag. The lower the number, the better. If we’ve done our job, the wheel will consume fewer watts than an OE wheel.

The results from the wind tunnel were better than we expected.  The charts below show the Total Power watt values for the FLO All Sport Series when compared to our existing wheel line and a Mavic Open Pro.

The panes below expand to show the Total Power values for the FLO 49 AS.

The panes below expand to show the Total Power values for the FLO 64 AS.

The panes below expand to show the Total Power values for the FLO 77 AS.

From the data above we are able to estimate your total time savings when using the FLO 49 AS, FLO 64 AS, and FLO 77 AS when compared to a Mavic Open Pro. It’s important to note that the wheels come in rim brake and disc brake versions.  

We’ve been able to increase our internal rim width from 17mm to 21mm, optimize rims around much larger tires, and even reduce the depth of our FLO 90 to a FLO 77, all while creating faster wheels. We hope you enjoy the new line as much as we do.