I wanted to review Spiuk’s new, very flash TT helmet, the Kronos. But, absent wind tunnel data, all I could’ve done was yammer on about how pretty it is and how it makes me a total chick magnet. Or maybe I could’ve written a thousand word essay about my taint, but apparently I’m more reticent than some people. So I did what any reasonable person would do: I built a rig to measure the drag of TT helmets. (Full disclosure: Spiuk is a team sponsor, so I was sorta hoping the helmet would do well.) (Full disclosure 2: measuring TT helmet drag doesn’t make you a chick magnet.)

I know, I know, my place is a mess.

The rig is built around an old wheel. A crossbar is attached to the wheel, which is mounted in a workstand laid on its side. The wheel’s there just for its bearings. A styrofoam head is attached to one end of the crossbar. Monofilament is wound around the rim, then goes over a hub acting as a pulley, and a basket is hooked to the end. The crossbar only rotates a few degrees. When the forces balance and the crossbar teeters 3-5 millimeters from one of its stops the basket is removed and weighed. I rented a fan that blows up to 22 mph, reasoning that the greater the drag force, the more the rig’s friction would be negated. The rig turned out to be amazingly sensitive – a mere 1.5 gram washer could make the crossbar move.
Of course, the setup is flawed. Even though the channel of air is pretty focused (about 2′ in diameter), it still blows on parts of the rig, adding to the total drag. The airflow is certainly less consistent than real world conditions. The foam head is smaller than a typical head, and the whole thing isn’t attached to a body or a bike. So take these results with a grain of salt.
I ran tests with the Kronos, my Garneau Rocket, my Spiuk Nexion (a regular helmet), and the head alone. Each was run three times and averaged. The numbers are meaningless in absolute terms.

Kronos…………………120g

Rocket…………………128g

Nexion…………………178g

Bare Head…………….108g

The bare head number might seem low, but as stated earlier, the foam head is small. I took frontal shots of my disturbingly pointy head next to it and found that my head’s about 1.2 times bigger. And since drag increases in direct proportion to frontal area (I’m assuming the two heads have the same coefficient of drag), my disembodied head would have registered about 130 grams (or less, depending on how much the crossbar is adding to the total drag). Assuming that number is accurate, then these TT helmets are faster than a bare head (you listening, Mr. Fignon?). I’m sure one of those slim illegal fairings (that don’t offer protection) would be even faster. And of course, a TT helmet is much faster than a regular helmet.
If you read the data as ‘how much drag does the helmet add to the base rig’, you get the Kronos with 12g, Rocket 20g, Nexion 70g. Interpreting the data this way would mean that the Kronos has 60% of the drag of the Rocket. I’m not positive this is the correct way to read the data, but if so it’s quite surprising. I suspect the Spiuk’s closed bottom has something to do with this.
Next I added a flat panel under the helmet to simulate a back. Would the Rocket lose its disadvantage if its open bottom sat flush against a back? I did runs with the helmets as close to the panel as possible, and with the helmet tails 3″ off the panel. Once again, three runs each.

Kronos flush…………………112g

Kronos raised 3″……………121g

Rocket flush…………………128g

Rocket raised 3″……………130g

Bare head……………………106g

This was pretty surprising. The Spiuk got a bigger boost by sitting flush against the ‘back’, while the Garneau basically saw little or no change. I have no clue as to why this is, but I do know that you better not drop your head and let that helmet come off your back.
Time for Hate
Well, it’s $230. But it is pretty and fast.
Where does that leave us?
I’ll try to amass more helmets and do more testing. In fact, if you’re in the NY area and have a LAS, Rudy, Bell, or Uvex (I have a Giro lined up already), drop me a line using the ‘info’ link in the top banner. I’ll also try to get in some other dumbass pseudoscience experiments – saran wrapped helmets, shoe covers, mankinis, whatever.