Great to see some 3rd party testing of this helmet. It’s ugly as hell, but won’t stop some from buying it if it was super fast.

These guys are doing an amazing job of answering some of the key questions of the day on tech in tri at the moment. Socks, sleeves helmets.

Looking forward to seeing what they thinking of the Aerohead2.

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Regards, Richard
3D Bits and Pieces - https://www.printables.com/@thetrickster_793480

I tested the TT5 against the Mistral, Drone, OG Aerohead, Redeemer from Sweet Protection, Lazer Volante and the Uvex Race 8.

It was tested in the windtunnel in Silverstone.

Tested at 30 km/hr, 40 km/hr and 50 km/hr at 5 degree, and 40 km/hr at 0 and 10 degree.

The 2nd fastest was the MET Drone - but it tested so close to Mistral, Redeemer and Volante - like within 1 watt.

The TT5 was 4.6 watts faster than the Drone - and LUCKILY the headsock only gave me an extra 0.7 watt.

Just to be clear - no sponsors - just looking for the fastest helmet for me.

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Long Distance PB: 8:25
Instagram: larsschmidttri

Nice to see a video on this but I do think Jim needs to know/state the typical,+/- error he gets using his preferred method of aero testing. A few more details in the videos on his methods too would give them greater credibility.

Having tested with Jim outdoors twice I know his procedures with this type of testing. Not to give too much away, but he doesn't just run numbers on one pass or one loop of the bike track, but multiple loops with each change. Jim can see each loop and CDA to tell the overall story of drag with each testing subject (wheel/ helmet/ position) used within those multiple loops.

Its super interesting to see what bike change 'feels' fast or slow and how the actual numbers actually stack up. We learned some real interesting things about front wheel types...one that kind of shocked Jim. But like everything, its is rider dependent. The Mistral didn't testing quite as fast as my Rudy Wing, and my big drop in CDA was achieved by reaching out more with my pad position not by going lower in the front.

This really is important though. Without knowing the +/- of the results, the obtained values are highly questionable and not remotely scientific or robust. Having a three rider sample is essentially a small series of case studies - that’s fine - Jim admits as much and explains well why he tests who he tests. However, the error of each riders testing should be shown (even if the methods are hidden as you suggest). Mind you, this is a major failing of the industry in general and few (with the possible exception of Aerocoach occasionally) ever include such details in their aero testing data.

I get what you are saying. I look at it like FTP testing..you test to see what that number is for you on that bike on that day. We test the base CdA, but not just 1,2 or 3 laps, but 6. Average the CdA. Make the one change (helmet/ wheel/ position) do the 6 passes and average that CdA. Regardless if the CdA is 'correct' or not, you are basing the numbers on that rider, one that day, their bike, set up, weight, same terrain and wind conditions.

If your base CdA is .2475 with Helmet A and after 6 passes of testing it gives a CdA of .2544 we can surmise Helmet B is slower on that rider. Now if it is a closer number, either higher or lower, then you get into what is more comfortable on your head, gives best ventilation, best field of view, ease of strapping on, etc.

Obvious to state, but one item will test different on another rider, BUT looking at the overall numbers from various riders will give you an overall sense of the aero nature of the item being tested.

Maybe in the wind tunnel the +/- of the more static testing is more quantifiable? Testing a lone wheel/ frame or a combination with a mannequin or even a human is going to give you different numbers in that environment than in the wild, thus the importance of individual testing outside.

Funny you mention Aerocoach as my Zephyr wheel (with same tire brand/ size) tested slower than my current race wheel (one Jim has not been a fan of). Not to say its a slow wheel for another person on another setup, but for me it was on mine.

Oh, I agree that the measured CdA is unique to a rider, a relatively arbitrary value and the difference between that an another equipment change made is purely a relative one. That’s really not the issue. However, whether you test inside or outside (or whatever method you choose to use), you should know it’s +/- (or essentially what is its ‘precision’). That measurement error is quantifiable and frankly if any tester doesn’t know what it was, then they haven’t tested properly and their results then lack robustness.

Most good field testers will know what typical error or precision they get with their testing process. Whether anyone’s formal testing has rigour and their results have statistical significance (such as this video) is a huge question a mark for me with the information as he currently presents it (as fun and interesting as those videos are).

One of my first lessons in physic studies was that a measurement is only valid if you have a clue of the error (or the precision, the bias, the accuracy, different disciplines use different terms). If one doesn’t know the error, at least state that one doesn’t know it and estimate it.

I was further taught to round off a measurement value so that the last significant digit gives the error.

It is just amazing how good the cycling scientists are in metrology, giving often 4 or even more significant digits.

How did the aerohead test? This is the Giro one correct?

Yes - Aerohead is the one from Giro. I tested it to be 8 watts slower than the TT5 :) It was almost the same at 10 YAW, but at 0 and 5 it was waaaaaay worse :)

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Long Distance PB: 8:25
Instagram: larsschmidttri

This is a great video. Nice to see Jim making so many of these testing real triathletes on different setups. I agree it's often tricky to pin exact numbers on gains, but I feel each of those triathletes left the test knowing which helmet is fastest for them.

While I haven't tested the Specialized TT5, the Mistral has worked very well for my high head and front end position which is similar to that first rider. I feel that helmet alone allows me to run my aerobars a couple cm's higher with no penalty.

While the Mistral always seems to test fast - Alex Dowsett's recent shootout video showed these same helmets finishing top 2 - it's interesting to see the same pattern where the mistral can really break out for riders that like relaxed or higher front end positions so if you're one of them definitely try one!

Dean