Well shoot. Dylan spills some of my best gravel aero secrets

Basically for free. Dylan, what are you doing? :joy: :joy: :smiley:

I’m going to lose my ‘most aerodynamic gravel bike in the world’ designation.


Wind tunnel video results are always interesting to watch. I agree with Dylan that aero socks seem to get a lot of hate but are a cheap way to potentially get watts. I say potentially as a poster over at slowtwitch (Desert Dude) who has been to the tunnel with hundreds of different athletes has said that some see large benefits and others see zero.

But what I really want to know is how many extra watts Dylan would need if he moves his head around as much on the bike as he does in his videos vs keeping it in one position :laughing:


Yeah. Well, what I would say is that Dylan left out a large part of the data…and that is how the various things that he tested behave at various yaw angles. He gave a lot of talk time to how aerodynamics can impact race times of slower riders…but not much attention to how yaw angle on the same course in the same wind can be dramatically different for those two cohorts of riders (average human vs pro human).

Aerodynamics on the bike is super important…but once your mind starts to morph total aerodynamic impact with the effective angle at which you interact with the wind, aerodynamics become an absolute weapon. Based on where you are on the course and the speed of the group you can really see (in your mind’s eye) that ‘aerodynamic advantage’ slider moving up and down.

Especially in gravel this can be a big, big weapon. For what should be obvious reasons. :smiley: Even if you echelon on gravel the riders in the loosey may still be getting a net disadvantage.

Anyhow, some of the things that Dylan mentions have outsized advantage at higher yaw angles. Some of them have moderate advantages at higher yaw angles and slight disadvantage at low yaw angles. So yaw is a big part of this story that Dylan decided not to tell you. For most, that’s nuance that doesn’t really matter…but it can really make a difference.


For the aero socks aspect, aren’t high end aero socks not like normal socks in comfort and how they stretch out easy and then don’t stay up which makes them add drag. So a sock that is more aero but can still be worn like a regular sock would be better for normal use

Not the Silca sox. They’re some of the most comfortable socks I own. :smiley: And they don’t fall down…I guess ever as far as I can tell.

Rule 28 sox are TT sox. Not uncomfortable but not something you’d wear around the house. And their useful life is over not when there is a hole in the toe of the sock but when the silicone gripper will no longer hold up the sock. If you buy those or similar sox make sure you throw in the price of a can of stickum or spin-It.


good stuff. Have you ever done field testing of aero outside? I’ve done it for years, the best results seem to be in either a steady strong wind, or no wind situation. And of course an ability to hold erg-like power in various positions. With that it is possible, in my experience, to see position changes that result in 0.2-0.3mph speed increases/decreases. Not very exact, but its free and you can test at anytime with varying degrees of success/failure. With enough tries it does appear to be repeatable. Interestingly, and consistent with Dylan’s testing, my most aero position from field testing is usually the aero hood position.

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I understand why one would want to test each thing independently, but what I would like to see is someone start with their position, then add in helmet, then add in socks, water bottles/hydration pack, and etc.

Supposing Dylan did this, determine which socks/hydration pack/etc. he was going to use, then does adding in the large saddle bag actually help? Does it help to the same extent?

I honestly have no idea how this works, but here is my thought process: suppose it takes me 220 watts to pedal at 21.7 mph when I am perfectly optimized. If I move up to hoods, I am now at speed scaled to 190 watts (34 watt difference in video). Now if I switch socks to non-aero socks, since I am no longer at 21.7mph, the wattage penalty ought to be different.

Not only that, but we know aero gains are individual. As such, I could imagine that combining the USWE hydration pack and the large saddle bag might change the aero benefits of each.

Last thing: Suppose the group you are in is going to finish with average speed of 21.7 mph. I’d be interested in knowing how much these aero improvements reduce total energy expenditure for the race. The way I see it, the biggest benefit might not be that I literally go faster but that I have saved more energy if it comes down to a sprint finish.


and change depending on wind direction, a point that @Brennus raised upthread.


:notes: “Shave and a haircut…2w” (actually its more)

edit: I’m old so not worrying too much for that speed, but actually something like added or saved 5w is quite much for like 4-5 hours as w = J/sec

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I had a modest tailwind on Sunday, and saw 20 mph for 130 watts on the flat. Twas lovely.


Last night it was a little windy, from the weather something like 20-26mph.

Two Strava segments, one out, one back, and I turned around at the end of the first and immediately (same wind, temp) did the reverse segment.

  • 13.9mph at 199W
  • 23.2mph at 191W

First was heading due west and SW winds. Reverse was due east, a minute or two later.


Awesome vid!

Really wish more races would use stick on seatpost numbers like they do at the Dust Bowl 100. So simple to mount and out of the way…


So should I wear Silca aero socks at Unbound this year? And will they guarantee that I beat the sun?

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Since you are wearing socks anyway, why not just wear the Silca? I have been wearing them since they were released and they are great socks. I even wash/dry them after every outdoor ride and they show no real signs of wear and they still stay up on my leg.

For myself, I need to get some new handle bars/stem combo that will let me ride aero in the hoods.


@aydraper you vs the sun is a classic conflict like mongoose vs cobra or roadrunner vs rattlesnake…nobody can know ahead of time which combatant will emerge victorious. That’s what makes the conflict so mesmerizing.

All I can promise is that if your feet are uncomfortable at the end, it won’t be because of your sox. And if you are slower than planned, it won’t be because your sox are bunched up around your ankles. And even if you crush the sun, retire in victory, and ride off into the dead body of your enemy, you’ll still be able to wear your sox around the house in comfort.


@aydraper, serious answer this time: I think it’s better to wear just any old low sock along with a set of triathlon aero compression calf sleeves. They cover more skin. They are more secure. The added compression decreases aero drag even if the trip lines are a little out of place. For a long ride like DK200 I believe the compression provides some additional comfort/relief.

From my studies on the matter, I would agree with Dylan’s findings that the Rule 28 sox are faster than the Silca. But IMHO that’s because the Rule 28 sox I tested are about twice as long. But, also in my tried and tru experience, the Rule 28 sox last about as long as a pair of velotoze shoe covers. They are just not a durable item and they’ll start slipping fairly soon if used in a gravel capacity.

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100%….but honestly I kinda doubt their aero claims (especially for the original height socks).

But they are damn comfortable, so why not wear them if you have them. Only downside is they are kinda stoopid expensive (but what Silca product isn’t).

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I had seen the results about the 1L bottle in your jersey pocket earlier today, but I am still blown away by that result.

I hate bottles in my pockets so no way I am doing it, but fascinating result.

And looks like I am gonna have to order a USWE pack. :crazy_face:

(Nice shade thrown at Stetina in the video, also. :joy::joy:)


I’m guessing “number behind seatpost” also gives you an aero advantage, because the airflow looks a bit better.

I never really understood why you have to have a number on your bike in gravel races. Why can it not just be on the rider?

Same reason triathletes have a helmet number on the front….so they can tell who you are and sell you pictures from the event.

That and “tradition”.