If you’ve ever owned a disc wheel, you will know that the only part of the wheel that is not covered, is the valve cutout. We are often asked if covering this valve cutout will improve aerodynamics. To be honest, we didn’t know the answer, so we studied it.
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What We Tested
In November of 2015, we visited the A2 Wind Tunnel in North Carolina. We tested a FLO DISC in the wind tunnel with the valve cutout covered, and then repeated the test after we removed the covers. Here are a few more details.
1. The same wheel was used for each test.
2. We used a Continental GP 4000 S II tire in a 23mm size for both runs.
How We Tested the Wheels
We like to describe all of the details of our testing so the results are as transparent as they can be. Here is how we tested both wheels at the A2 Wind Tunnel.
1. Tare was calculated and removed from both tests.
2. Each test swept the wheel 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. Each measurement was taken twice and averaged.
4. All tires were inflated to 95 psi and calibrated with a digital gauge.
The results were very similar. The Yaw vs. Drag graph below shows the FLO DISC w/ Valve Cutout Covered (in blue) vs. a FLO DISC w/ Valve Cutout Not Covered (in green).
I would cover the valve cutout prior to a race. If in the middle of the race you flat, I wouldn’t waste my time recovering the valve cutout.
What is the Best way to Cover a Valve Cutout?
You can purchase special stickers to cover your valve cutout, but our personal favorite solution is using 2″ wide electrical tape. The material is very similar to the covers you can buy, it sticks well to contours, and it’s not impossible to remove. Another benefit is that a roll should last you several years.