Thanks rsbob. I saw that eval previously.

I'm not as sure this is true as you seem to be. Both aero road helmets and TT-specific helmets used to be pretty sensitive to position. The big revolution in helmet designs in the last few years is to make both a little more robust to positional changes. That is, the best TT-specific helmets now aren't that much more aero than the best TT helmets from a few years ago under ideal conditions: however, the new helmets appear to be better under a wider range of yaw and head position. That's one of the reasons why modern TT helmets "look" so much different than older designs.

That sounds like good news then. Do you know if aero road helmets are optimised around a more upright road racing position as I presume TT helmets are optimised around a TT position? Or are the differences mostly size/weight and ventilation?

Ventilation is a big issue nowadays and designs try to manage air flow both around the helmet and through the helmet. A large part of the flow management for TT helmets is how the air comes off the helmet and interacts with the flow coming around your shoulders and down your back, and that's where a lot of the "robustness" focus is: even when you're not optimally positioned for the given yaw angle, you don't want the air to stall. That said, a lot of robustness research has been going into road helmets too.

Thanks, that makes sense. I think I might get an aero road helmet next time. I currently have a Lazer G1 Genesis, which is a nice helmet, but more of a lightweight, ventilated design. It’s great for hot summer climbing, but probably not very aero.

You should go matchy matchy with the bike and get a Canyon/Abus Gamechanger:thumb: Some get aero helmets to also be their cold-weather winter helmet, assuming there's less air flow thru the scalp.

Isn’t there an aero insert for that helmet? But then it probably reduces ventilation to nil.

Since the OP is concerned about marginal gains, go to the Silca site for the Top 10 Marginal Gains
They include the Giro Vanquish as a top aero helmet.

Hmm, I'm not in the racer field, but I wonder if the new helmets have golf-ball-dimples or other "energy adders" on the aft quarter surfaces, to delay flow separation at off-angles of yaw and pitch?

Yes there is an aero cover available for my Lazer. I might look into it but as you say it could be too much of a compromise in ventilation for the long rides I do.

This thread just made me think that modern aero road helmets now appear to have little or no downside compared to non-aero designs, apart from maybe cost. If it saved 10W on the flat I’d consider that worthwhile.

Looks quite cool 😎
Doesn’t score too well in that review of aero helmets linked earlier, but a quality brand.

I saw that. But I also saw another article (can't find it now) that showed the Giro Eclipse Spherical being faster than the Vanquish in a real-world test! I know there is lots of marketing and, ultimately, I'm wondering if it all really matters to a guy like me. I wanted to spend the money for an Evade, but I'm going to get a Bell Z20, as I already have a Bell Formula and it fits like a glove.

I wouldn’t necessarily count on the Bell fit being the same, although it is a bit more likely. I have personally tried helmets from the same brand and found that their fit is not consistent. So make sure you get to try it on before buying. Don’t assume it will fit the same.

I'd love to try it on. But I'm very limited. We have a Trek store that selss Trek, Bontrager and such. There's another bike store that has a limited number of Specialized helmets. Other than that, it's Dick's or Walmart. I think most of us are in the same situation. I was looking at a Giro helmet, but if I want to try it on I'll be purchasing it through the mail.

In that case make sure they will accept returns if it doesn’t fit. Some shops are reluctant to accept returns on helmets unless there is a defect.

I know. Thanks. And I hate returning stuff. But I believe that the Z20 has the exact same fitting device as my Formula. If so, I'll probably good to go. I have to be sure of that.

I think there were some helmets in the past with "textured" surfaces but they must have been a dead-end cuz I don't think they're still using that.

Speaking of dead-end aero research, there's this: https://www.researchgate.net/publica...Maid_Character

Dimpled helmets really work, but you need to be able to spin your head around and around constantly. That's why they didn't pan out.

Top class 👏

I like to keep two types of road helmets in rotation, one that favors ventilation and lightweight for routine training, and an aero helmet for go-fast time. I'm also a time trialist an have a couple TT specific helmets that I have been testing using the Chung method. In case you guys didn't know, RChung is a bit famous in the TT/aero community.

I'm now looking hard at the Giro Eclipse Spherical. Can't seem to find the Z20 in the size/color combo that I want. Do Giro helmets fit oval heads well?

Not quite dead-end if they use live subjects in a wind tunnel. And who said research was boring?

Pretty soon the pro peloton will be sprouting man-boobs for aero-gains and the women will all stuff their bras to become double Ds.

Hey all. As an update, I purchased a Giro Eclipse Spherical helmet. It's marketed as being faster than the Vanquish. I got it on direct from Giro on a sale price of $187. The price is back to $250. Quick review: smaller that I expected, light, and fits my oval head very well. The retention system is pretty nice and works well. I only wore it on one ride in 106 degree weather and it was "venty" enough for me, and that was with wearing a bandana under it. My head never felt overly hot, but that can be that I'm used to very hot conditions. YMMV on that point. I will say that compared to my Bell Formula Mips, I "noticed" the Eclipse while riding with it. My attention is never drawn to my Bell when riding, like it's not even there. Yet I'm wasn't bothered by the Eclipse. As for it's aero-ness, I have no idea. It feels like it moved a tad "cleaner" when on the aero bars, head down. My wife thinks I look sexy with it on. Overall, nice helmet. Nice looking also.

Interesting. Now what you need to do is ride a fixed route one day with the Bell and then the same route the next day (provided conditions are the same) with the Giro and see if there is any quantifiable difference.

Why wait a day? Protocols for field testing to compare drag between different equipment setups or positions are well established, e.g. virtual elevation.

I suggest a day only because I would expect any data to be worth having would require a long enough ride that conditions would likely be significantly different between the start of the first ride and the start of a second ride. I mean, if we're just talking about any potential aero advantages out of a helmet, I would probably want a minimum of a 30 mile ride at effort to give a data point that could be compared. And that would mean almost certainly a minimum of 90 minutes in between start times. In the summer that could be an 80* start for the first ride and a 95* start for the second. At least out here. And that would not give you any time in between for rest and refueling. So if you factor that in, I imagine you would need a minimum of 30 minutes in between, further increasing the weather variables.

I simply don't believe you could get any useful data from a ride much shorter than that. It would allow far more variables to enter into the equation. But then again, to have any real validity, I would expect to repeat the experiment a minimum of three times in each configuration.

But that's just me.