Two Wheel Blogs

I got another rude awakening this morning at 4:45 AM when my alarm went off. Time for more aero testing at the Centaur Road wind tunnel.

Today's test was one I had been really looking forward to. I had in mind a head to head test of timetrial helmets. Today I tested a Giro Advantage II against a Louis Garneau Rocket.

I don't remember if I mentioned it before, but a couple of weeks ago Andy Coggan and I wrapped up an aero testing session by switching helmets. He took my Giro Advantage II, and I took his LG Rocket. We each did a single pair of runs - just two data points each - in the hope of getting some idea about which timetrial helmet was faster.

What we saw led us to believe the LG Rocket was indeed the faster helmet. On my head, Andy's Rocket asked me to produce every so slightly less power than my Advantage did. Andy saw a slightly larger difference. For the both of us, at least with on small sample of data, it looked like the LG Rocket was the faster helmet.

But one small sample of data is hardly conclusive. So I decided to take a break from my quest to find a more aerodynamic timetrial position and spend one of my wind tunnel sessions testing the Giro Advantage against the LG Rocket.

Andy had a pretty good idea for how to carry out a test that would yield reasonably reliable results. The method called for making two runs in each direction through the wind tunnel at each end of the speed curve. This would produce a total of 16 data points, 8 for each helmet, with 4 data points clustered at each end of the Power / Speed curve. That's the curve I've attached below.

If you look closely at that curve you might be able to tell it's really two curves. The Power vs. Speed curve for the Giro Advantage is nearly indistinguishable from the Power vs. Speed curve for the LG Rocket.

That's not to say that these helmets are aerodynamically equals, not by any stretch. In order to say that I'd first want to do a lot more testing. For one thing, there are a lot of variables I'd want to consider. I would like to test to see if taping over the air vents changes the results. Some believe these timetrial helmets are faster if the underside of their tails are enclosed.

Conclusion: At the end of the first round of timetrial helmet testing between the Giro Advantage II and the Louis Garneau Rocket, I can only declare a tie. If there is a difference, it's too small to matter.