GoPro confirm how much drag an on bike camera causes

As much as we’re all very grateful for all of the on bike footage, it does raise the question that when a race can be lost by seconds and marginal gains is the phrase de jour, how aerodynamic is an on bike camera? Are the riders sacrificing performance for our viewing pleasure?

>>> Mark Cavendish’s new Venge

Thanks to some testing in the famous Specialized wind tunnel now we know.

Cameras on display

Although the camera below was only used during the neutral zone, it is a great example of how on bike footage has become so popular and sought after.

Also, at the start of stage two of the Tour de France a few bikes were seen with the older GoPro HERO 4 attached. The GoPro HERO 4 is substantially larger than the new GoPro HERO 4 Session, therefore you’d expect the former to create far more drag.

GoPro Hero 4 Tour

>>> Mechanic’s GoPro catches footage of crash aftermath

Test

The test results claim that the latest GoPro model accounts for close to one watt when a rider is travelling at 45kph or just over 28mph. When riders are travelling over 100kph (as Mark Cavendish has done in this Tour de France) the GoPro’s impact on drag will have been greater.

https://twitter.com/MarkCavendish/status/621373948832403456 

>>> GoPro launches tiny new HERO 4 Session camera 

At 1 minute 57 into the video there is a good screen shot of the results table. The table refers to CDA, this stands for Coefficient of Drag Area which is measured in m2. In short, the lower the CDA the more aerodynamic the position, and from the CDA you can work out the wattage required to ride at a set speed.

 >>> CDA system used to calculate aerodynamics

If you look closely at the screenshot you’ll see that when travelling at 45kph the Venge’s drag was 79.5 watts. With the new GoPro mounted on the front of the bike the drag increased to 80.3 watts. This equates to the GoPro HERO 4 Session creating 0.8 watts.

The new GoPro is 50% smaller than the HERO 4 (Trusted Reviews)

The new GoPro HERO 4 Session is 50% smaller than the HERO 4 (Trusted Reviews)

Interestingly, placing the GoPro at the rear of the bike produced slightly less drag of 80.2 watts. Lastly, the table shows that the new GoPro creates less drag than its predecessor the HERO 4 which created 82 watts- a not insignificant extra drag of 2.5 watts compared to riding without a camera.

>>> Garmin announces new action cams

So, although the extra drag created by an on board camera is not huge, it does show that mounting an on bike camera has a negative impact on performance.