Time Trialing - The Helmet Conundrum

Hi,

Have you tried using the MET Codatronca? It comes with a shorter tail so perhaps easier for your positioning on the bike. :blush:

No I havenā€™t, but it is in my list.
I am trying to make one of the long tail ones work first, with them presumably being faster when used ā€œcorrectlyā€. Doesnā€™t mean that is true, I will try the shorter ones too.

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Out of interest, how did you do this?

The old way, photo and pixel counting or via greenscreen, like the bioracer system??

I did a full profile analysis with a bike fitter/ bio mechanics expert, to find a very aerodynamic yet powerful position for myself. Several cameras were filming me, while riding the rollers. The tool than gave a A and an estimated CdA and speed based on certain metrics.

Coolā€¦ what did it estimate your CdA as?

Donā€™t have the exact number atm, but just under 0.2

Did a little more testing today. Kask Bambino Pro Evo, Bell Javelin and S-Works TT again.

The Kask Bambino Pro Evo: a light weight, high quality ax great looking mid-long tail helmet. With the little ā€ždropā€œ at the end of the tail, it get closer to the back, and therefore looks a little better in position than the mistral. It is very light an comfortable to wear.

S-Works TT: I gave this another try. An aerodynamicist advised me to try going mega low at the front and from the video I send him, he said that way it might work well for me. Biomechanically, I donā€™t think I can produce much power that way.

Bell Javelin: pretty underrated helmet actually. Very easy to have it have it cling to the back and also look well around the shoulders. It is also by far the lightest helmet I have tried so far (373g in L without visor. Kask Bambino 404g in M).
The quality of the helmet however feels worse than on the S-Works and the Kask. The covers over the areas are flimsy and make creaking noises.

The Bell is definitely one Iā€™ll try out in wind tunnel and outdoor testing. The Kask Bambino pro Evo also looks like a winner.

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This is only eyeballing it, but to be honest I think both the Kask and Bell would ā€œlookā€ better if your pads and extensions came up 20-30mm. You seem quite low in the front which causes you to tilt your head back up to be able to look forward. Thatā€™s why none of the helmets flow wel onto your back if you see what I mean. You have a V-shape between the tail of the helmet and your back.

Even though itā€™s not a direct side shot but the MET seems to look the best in that regard.

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You are correct. Getting a smooth transition from helmet to back is a little easier, when the rider is a little more upright. However, such an adjustment is of course associated with a cost.
Too low front can mean: head coming too high, increased Cd, too tight hip angle (lower power), decreased stability, lower back pain
To high front can mean: higher frontal area, less control in wind (due to less weight on the front wheel), increased distance between base bar and arm cups is bad aerodynamically
For me, the current position has tested faster than the one I previously had. What I did is decrease stack height bei 20mm, move arm cups further apart and the extensions closer at the front. Saddle further forward to increase hip angle.

This is a comparison of positions (just some random shot from one of many runs, only goes to show the effects on frontal A ):

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Ahaa I see, nice validation work done already!

If you were to keep that same position, I would have a look at the MET Codatronca or HJC Adwatt. Theyā€™re short tailed but might be easier to have a nice transition to your back instead of leaving you with a dip between helmet and back?

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Maybe someone here might know, currently using a Bontrager Velocis but got a Poc Ventral air for better ventilation. How much ā€œaeroā€ am I really giving up?

Iā€™ve never seen data on either one, but using my oft-miscalibrated eyeball wind tunnel, Iā€™d say a decent amount.

And more due to the size of POC helmets vs. the ventilation holes. Those things are just huge on most people and wider is not aero. (Amd the design itself is not particularly aero either)

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Google brings up this from Michael Hutchinson, 1min over 40km.

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Seems like a much better value than an Aero road frame which IIRC nets around the same gain. Mine isnā€™t full aero but maybe semi, and the more I looked at the Poc the more I got the feeling that despite their claims (with no testing to back it up) it doesnā€™t look like Aero was a thought in its design, aside from the sculpted rear.

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I found a link that references Poc, aero and TT helmets in a wind tunnel and I think it says similar.

Granted Iā€™m not racing or doing TT but most of my rides average 20+ mph so Iā€™m sure the difference is not insignificant. Just because I sweat probably doesnā€™t mean I need to completely disregard aero

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@Cleanneone98 Iā€™ve tested that velocis helmet many, many times because each time I test it, itā€™s so good I say to myself, ā€˜I must have screwed something up there.ā€™ On my noggin its faster than some purpose built time trial helmets. Donā€™t know why and even now as I type itā€¦itā€™s hard to believe.

But the velocis is pretty good for a regular ole road helmet. My guess is the ventral would have a hard time approaching that level of aerodynamic benefit.

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I can notice the difference between my first gen Evade and my newer Evade II.

For me, the first gen is much fasterā€¦I believe it is due to the size vs aero design. Both are SM, but the Evade II is noticeably larger in size.

Tomorrow will be our normal fast-paced AM group rideā€¦temps will be 63* and it is gonna be a packed house. It is gonna be VERY fast and I am absolutely wearing my old Evade (and a skinsuit!)

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Thanks for the feedback guys. I cancelled my POC order, realized I may have jumped to the opposite end of the spectrum a bit hastily. Iā€™ve also been lagging on my haircut upkeep with COVID so I think the mop on my head is not helping my cause here. I donā€™t want to detract from the TT aspect of this thread too much longer but really appreciate everyoneā€™s help.

Great post and details, especially with the pictures. I know you are looking for the best helmet, but my wondering is, is your fit really dialed in? Your position doesnā€™t look comfortable or sustainable and you have a pretty significant hump in your back. Is your saddle too far forward? It looks like you can barely see up the road as you are so compressed. Iā€™m wondering if you moved back a bit it would allow you to see better and be more relaxed.

Just a thought.