Back in November, when Chris and I went to the A2 Wind Tunnel to test the new FLO 45, 60, 90, and DISC, we decided to study a few things we’ve thought about over the years. Today’s article looks at the difference in aerodynamic drag between a standard build and a clydesdale build wheel.
|Testing at the A2 Wind Tunnel|
If you are interested in our other studies from the A2 Wind Tunnel, please be sure to check them out.
What We Tested
When you order a clydesdale wheel set from us, you get a different rear wheel. All of our front wheels are built with 20 spokes in a radial lacing pattern. Since the rear wheel is the only wheel that is different, we tested the difference between a standard rear wheel and clydesdale rear wheel in the A2 Wind Tunnel. The specs of each build are as follows.
Standard Build: 24 spokes, two cross build, on both drive and non-drive side
Clydesdale Build: 28 spokes, three cross build, on both drive and non-drive side
Here are the details of the test.
1. We wanted to maximize the spoke length in the wheel to find the largest difference in drag possible. We used rear FLO 30s for the test because they are our shallowest rim, and as a result, have the longest spokes.
2. The wheels were built with Sapim CX-Ray spokes.
3. We used the same Continental GP 4000 S II tire in a 23mm size to test both wheels.
How We Tested the Wheels
It’s important to define how a test is performed in a wind tunnel. There are countless variables, and if you are not clear about the test, the results are not very clear. Here is how we tested the wheels at the A2 Wind Tunnel.
1. Tare was calculated and removed from all tests.
2. Each wheel was swept from 0-20 degrees of yaw, in 2.5 degree increments. The drive side of the wheel was opened to the airflow as the angle increased from 0-20 degrees of yaw.
3. The same tire was used for each test.
4. Each measurement was taken twice and averaged.
5. All tires were inflated to 95 psi and calibrated with a digital gauge.
The results were surprisingly similar. The yaw vs. drag graph below shows the rear FLO 30 standard build vs. the rear FLO 30 Clydesdale build.
To determine what this means from a time perspective, we calculated the time savings for each wheel when compared to a Mavic Open Pro with 32 round spokes. The Open Pro used the same Continental GP 4000 S II tire in a 23mm size. The time savings were calculated using our Net Drag Reduction Value formula. We developed this formula after collecting 110,000 live data points with a custom built data logger that was mounted to a bike. If you’d like to learn more about this process be sure to check out the Five Part Series.
We can see that the difference over a 40km and an Ironman is 2 seconds and 6 seconds respectively. In the grand scheme of things, the difference is very small.
Should You Be Worried About Using a Clydesdale Build
Now that we know the aerodynamic difference for a Clydesdale build is nothing to worry about, let’s look at the most common questions we get when we recommend someone moves up to a Clydesdale build.
How much more does the Clydesdale build weigh?
The weight difference is about 30 grams. While 30 grams may seem like a lot of weight, the time difference from a weight perspective is pretty much 0 seconds.
If you find yourself contemplating the Clydesdale build, and are worried about weight or aerodynamic losses, do yourself a favor and size up. While I have not studied the difference in power transfer between the two builds, I would wager a bet that a heavier rider losses more time due to inefficient power transfer from being on a wheel that is not strong enough for them. On top of that, you’ll have a wheel that will stay truer longer, and maintain it’s warranty with us.
I hope you enjoyed this article. Please feel free to comment and ask questions below.