These in-depth scientific studies always seem to neglect the weight and aerodynamics of the RIDER. That is surely the biggest factor when it comes to speed and efficiency.
But reading "The secret race" by Hamilton (one of Armstrong's team mates), they do focus obsessively on it. They would often ride for hours, then take sleeping medication and go to bed without eating.
It's definitely very significant for european-style touring races, but people overstate it for even high-level amateur rides especially in flatter areas. Which is most gravel riding.
Ah, the smell of fresh gatekeeping in the morning. You don't know what road these people are on, just their current state. For all you know, they've already dropped dozens of pounds and are happy with their own improvements. Never look down on a fat person on a bike.
I'm a cycle advocate and spend hours a week fighting for infrastructure etc where I live, that I hope helps all kinds of cyclists.
The problem is that there are so many variables with riders. For example, just a slight change in head position can increase drag more than any improvement in frame tube shape could save.
They basically never test these aero bike gadgets on a rider.
Aero helmets and clothes are probably the only ones that get tested on riders in a valid way.
https://www.cyclingweekly.com/news/racing/check-illegal-sock...
Weirdly "aero socks" are both a thing and make a big difference to the point that they are heavily regulated by the UCI.
Any cylindrical part of the bike or rider is going to perform badly so if you can encourage the airflow to stay attached around it you reduce the amount of effort required to move you forward, hence aero clothing being a big deal.
If you're a serious cyclist then it's pretty easy to spend money on good quality clothing.
In addition after switching to a Brooks saddle (I tried literally 10s of saddles using the "saddle swap" forum feature on some forums) I now no longer ever want to use padded bike shorts again. Of all the short types the simple padded chamois was my favorite (simple foam - no gel or any other BS) and now I just prefer wearing a pair of synthetic lightweight boxer briefs (no fly) that were designed for hiking originally. There is no padding at all and from day one the brooks was extremely comfortable. It only got more comfortable with time and applies all pressure directly to my sit bones. Every other saddle + padded short (even ones that mostly were on my sit bones) ended up forcing padding into the areas between my sit bones and outside them as my weight compressed the padding. I havent tried their new non leather seats but they seem to operate by a similar tension (a tensioned pliable surface vs a hard plastic shape with padding on top) which results in your weight creating additional space below the sit bones vs filling it with padding.
In Michael Huchinson's Faster[1] it mentions that they tested a rider naked in a wind tunnel to find out!
If you look at a modern TT skinsuit you can see that they try to cover as much of the arms and legs as possible. They usually stop above the elbows and knees because it's hard to cover the joints without wrinkles.
Likewise, socks are now as long as permissible (without breaking the UCI sock rules!), which I think is about halfway up the calf. It would be faster to cover all the way up to the knee joint.
It all sounds silly if you don't race but if you've put some effort into getting fit then after awhile it's hard to gain even 5 or 10 more watts. If you can reduce your drag by more than that just by wearing a better pair of socks... well why would you?
BTW I have a Brookes on my commuter Brompton too. :D