lightheir wrote:

That’s super interesting regarding the lack of importance of tail position. You should start a new thread on it as it’s that counterintuitive

I was bored this morning, speculating is no fun and I don't have a wind tunnel :-)

So, this morning I went out and did 3x out&back. Each out&back is 11.4km (5.7 each way). Lower than usual traffic, maybe 10 per out.

In Green is the profile of the terrain. Rolling hills
In Blue is the wind, about 1km/h. The white is the average for the out or the back so you can clearly see the head/tail.

The bars show the CDA for the out & back. First one .248, then .248, then .246. Not bad.

Now. During the 2nd O&B I would do, 20seconds head down which for me raises the tail a bit, 10 seconds look up which flattens my tail. No difference in CDA.


So zoom into test 2 and 3, and I turn on the raw signal from an IMU we put in the helmet (in Grey). This way you see the difference between my intentional moving of the head and my natural head movement. I was not trying hard to hold my head

Plotting and explaining "instantaneous CDA" would bring us down a rabbit hole, so I plot Virtual elevation in red, setting it to .248. If the moving of the head produced a change in CDA we would see elevation step up or step down every time I did it. The "intentional" head movement O&B tracks the same as the "natural" one.

You see the VE rise on the turn arounds, as well as the helmet IMU as I sit up. VE re-syncs to elevation at test start.



In my case, flattening the tail does slightly raise my front area (we measured that) as DD suggest. Next time I get bored I'll show that :-)

Pulling the front plug makes the LG P09 faster? Seems counterintuitive if true. I had already stopped using the visor but have been keeping the plug in, even in warm, humid conditions, only because I thought it was faster keeping it in.

The Rudy Project you used in 2016 was likely the Rudy Project Wing 57, which I believe was not a fast helmet (where as the latest The Wing is reported to be fast on a lot of people), so in your case the aero road helmet you have been using may have been an improvement over the Wing 57.

 
That is correct, I had the 57 model. I wont use anything that covers my ears in heat moving forward, I just cooked. I found it a good helmet in other conditions,

I also had the Wingspan before the 57 and before the that I had the Syton! Remember Macca winning in that years ago I loved that thing and you could remove the ear coverings, I wonder how that would test v modern aero/ TT helmets?

So I am a pretty loyal Rudy Project Customer in general.

I'm no desertdude, but here's my guess as to why. The front of your head is a high-pressure area, so anything that can reduce the pressure on that spot. Take a look at the image from the Limar Air Pro press release. https://bikerumor.com/...s-astana-giro-debut/ By pulling out the plug on that spot, you allow better airflow by routing air through the tunnel instead of around the surface. So it's basically reducing the frontal area because the air can flow right through and out the back.

It's actually a simple solution. Instead of trying to move air around the helmet as smoothly as possible, pass it straight through.

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See your bike fit. https://bikefitr.appspot.com/

I thought I'd put 2 pics out that show difference in head position between tail up and down. Since a pic is worth a thousand words here are 2000 words. If I can find my Giro selector or bell Javelin pics the difference is even easier to see and the drag difference is even greater than with the Aerohead. I'll also tell you which was faster at the end. First let me explain what you're seeing, how it's captured and what the deviation might be.

This was the same run, just changing head position, captured from the same camera in the tunnel. 2 data points per position each data point is the average of collecting drag for 22sec (iirc 12 or16x per sec) then average out your drag over that 22sec long point to give you your final #. This run was ~ 6 min long just going between head lower and higher. Drag varied by < 20gm per 22sec data point, aka I nailed the consistency on this run. That's <.5w and the tunnel is sensitive to about a .7w change. The tares have not been removed. I tested at 0 & -10 yaw for each position

I went between 2 head positions, head lower and higher. A different way and, imo, a better way to frame the head positions is the top pic is I lined up in the sub 28min swim group. Why did all these people who can't swim start in front of me (PSA -don't be that triathlete)? The bottom pic is I'm through 15km into the bike, the course is pretty wide open, I don't need to worry about plowing into someone.

When I look up I'm forcing the bottom of the back of the helmet down towards my neck closing that gap. When I drop my head my overall frontal area decreases. (use the landmarks in the tunnel to see the difference in head position. (top of helmet to the light, chin to forearms gap etc)

Had the tail been longer would it have mattered? Not on me, with the aerohead, selector & javelin (if I can find those run pics I'll post them). If you lift your head to force the tail down will it increase frontal area? Probably as you can see from the pics you're raising the top of the helmet.

results for the curious
0 yaw head up .234 CdA
-10yaw .216CdA
0 yaw head lower .230 CdA
-10 yaw .214 CdA
FWIW I retested the Javelin later in this session after making some other changes that were faster at yaw
Javelin + 5mm more length on the extensions
0 yaw .236 (.006 slower than previous fastest run)
-10 yaw .221 (~.010 slower than previous fastest run)

Anyway hope that helps & any questions lmk





^^^^ why all the slow swimmers pic aka head higher
vvvvv head lower

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

What about also closing the gap between helmet and neck (with your head in the lower position) by rotating the helmet further back on your head, essentially making the writing on the helmet the same angle in both pics? This is the piece I keep bringing up - get your head position correct first, and then fit the helmet to that (preferably with the tail on your back), and not vice versa, no?

...and I love your Plasma 3, building one right now!

I'd still stand by my having the tail on the back matters less than having proper discipline with head position with the tail off the back. I know for me and the lower head is my normal position, that having a helmet pushed back/tail on the back wasn't worth it.

Most triathletes though, even at the elite ranks from the races I've spectated at, have poor head (and position) discipline.

Out of all my tt/tri bikes, 3 softrides which I Loved, QR lucero, Cerevelo P3X, one or two I don't remember, the Plasma was my favorite.

If I was still racing I'd be confident that how I set mine up was faster than 95% of everything else in the transition area.

Super easy to travel with. From opening my case to zipping it up I could pack it & all my gear in <20 min.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

Thanks for posting this. How about Areohead visor off and the Cda associated with that? You see a lot of people like the Blu, Gustav & Skipper rocking no visor. They're notoriously hot vs sunnies but what's the trade off in cda?

most of the time when I've tested it visor off vs on, off has lost.
Off the top of my head I can remember 1 win visor off.

I really need to do something at the wind tunnel where people come in and test 5 helmets, that's it. On and off in 15 maybe 20 min max.

Pretty soon I hope to be up and running with field testing here in Tucson though.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

Reviving this thread.

Would you mind clarifying if the front plug should be in or out for Max aero?

Also, with no visor (wasnt enamored with it, what is the recommended sunglasses option,? My challenge with sunglasses is that: 1 framed ones - frame blocks visibility in the aero position 2. Frameless. Top art gets sweaty and eventually causes visibility issues. Happy to learn and find a better way!

Thanks very much

Reviving this thread too :)

Something happened to my Kask Bambino during the winter in storage and I need to replace it. Whats fastest/best helmet now?
I was looking for Rudy The Wing, but their largest is size 58, while I need 62.


Specialized TT5 - is it worth it? Looks like something from star wars, but can you remove the sock? Will it still be comfortable/fast without the sock?

I saw some data where the sock was faster across the board and some data where at the lowest yaw angles (-2 to -3 or -4) without the sock was faster then the sock became faster.

The difference was small though, biggest difference was .004CdA at 30mph.

If I was going to go the TT5 route, I'd decide if I was the type of rider who is going to see very small yaw angles, such as < -5 for the majority of my race or the type of rider who was going to see a higher yaw spread.

Then once you figure that out you have more info to make a (hopefully) better TT helmet purchase decision. Could still be the TT5 or it could be something else

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

I think it depends on your head position. I have a Kask Mistral and a Giro Aerohead and it looks much better the Mistral (on me). Despite that it feels much more confortable :-)