Hey guys,

I don't want to jump into this discussion except to clarify the direct questions about our shield research. I've been MIA recently due to a busy few months so if I miss anything that I may be able to chime in on, just PM me to take a look and I'll get on it!

Anyways, what we have found is that a head is a fairly poor aerodynamic shape because it is a pretty good approximation of a sphere. Spheres are bad because (at the Reynolds numbers associated with the size of a human head and bicycle speeds) they tend to separate nearly at the point of max width/diameter and create a large wake region, resulting in high drag. Wearing a good aerodynamic helmet is actually faster than wearing no helmet since they shape the head into more of an ellipsoid than a sphere. Why do I bring this up? Because with the way visors are typically executed, the visor/helmet front end becomes closer to a sphere (by creating a smooth round surface from the front of the face onto the helmet surface) and separation migrates back out to the wide point - again, resulting in higher drag. We've found this in nearly every visor/helmet combination that we tested. In a way, it can be worse than wearing no helmet since we've created a sphere that is bigger than your head.

Now, to the point of why some helmets may contradict this and test better with a visor than without: The catch with not having a visor is that you have to manage the airflow inside and out the back of the helmet. With an open front, no matter how tight you wrap the sides of the helmet to the head, flow will enter. Unless the helmet has been designed to effectively evacuate this flow, this can result in higher drag. With some helmets, drag from internal flow stagnating can be higher than drag from adding a visor, so the net result is a visor is faster in that particular system.

Finally, specifically with the S-Works+McLaren helmet: the fastest configuration is with no eyewear. We realize almost no one rides without something over their eyes, but we wanted to be upfront about what the fastest configuration is. Next fastest is with sunglasses (this one depends on which model exactly with no real rule of thumb - but I don't recall testing a sunglass model that was slower than a visor on this helmet). Next is with a visor.

Sorry for the long winded response, but I like to get these things right/clear and with aerodynamics it's hard to be brief. Hope that helps, and again sorry for barging in on this particular thread!

I understand the general ideas of separation, pressure, etc..

Is it because the shield is effectively 'blocking' the air, instead of letting it find its way through the helmet via the paths of least resistance?

I really prefer a visor over glasses, but I'm getting the impression visor vs. no visor is not position/person dependant, it's sounding more & more like a universal truth.

Educate me.

Once data from the aerocamp last weekend at ERO starts to circulate you might see some data on the Wing57. It's up to everyone individually to post there data, but I think most are planning on it. Think about half or maybe just under that tested it.

The star of the show was the Louis Garneau P09.

Jim@EROsports wrote:

JTolandTRI wrote:

Once data from the aerocamp last weekend at ERO starts to circulate you might see some data on the Wing57. It's up to everyone individually to post there data, but I think most are planning on it. Think about half or maybe just under that tested it.

I'll leave the Wing 57 numbers to the campers. The star of the show was the Louis Garneau P09.

Is the P09 availible for sale yet?

I understand the general ideas of separation, pressure, etc..
Is it because the shield is effectively 'blocking' the air, instead of letting it find its way through the helmet via the paths of least resistance?

I really prefer a visor over glasses, but I'm getting the impression visor vs. no visor is not position/person dependant, it's sounding more & more like a universal truth.
Educate me.