If you are riding a course that warrants 2.2 inch tires (and in some cases a front suspension)… and with gravel bikes coming in at pretty much the same weight, what is the benefit of riding a gravel bike over a hard tail?
Primarily aerodynamics. Gravel bikes will get you lower and narrower.
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Gravel bike is still going to be a lot more aero. I’ve got 38cm bar on my gravel bike and in a much more aero position than on my hard tail.
Properly set up, being on the hoods is more aero than in the drops.
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Curious about this… Can you explain how this is possible?
The key is “properly set up”…you need to establish a position where your forearms are mostly horizontal and parallel to the ground.
In the drops, your arms tend to be extended more vertically and cylinders (i.e. the shape of your arms) are terrible for aerodynamics.
In addition, you can get just as low, or at least close to it, when you are on the hoods. Again, when properly set up.
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I’m still hoping that Specialized comes out with a gravel version of the SL8 that can fit 2.1s. To me that would be the ideal gravel race bike. Their current offerings seem to be getting long in tooth. For the first time I would buy a Ridley over a Specialized.
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chainring size and quantity.
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Agreed! I am convinced a more aero Crux will come out next year. Or maybe they repurpose the Diverge into an more racy bike with MTB clearance?
But who rides like that for a 100-200 mile gravel race? 
Thank you for the article! It says in conclusion:
If you translate all of that into time savings, the researchers say that on a flat 40km course (about 25 miles) with little wind and the cyclist riding solo at a constant power output of 300 W, he’d save about 45secs by swapping from riding upright on the hoods to riding on the hoods with horizontal forearms."
I don’t think those 45 seconds would happen real world over a 100-200 mile gravel course. Who can hold that position for hours on end?
Is the real question what are the aero differences between the bikes? Can you set up a hard tail similar to your gravel bike? Don’t some pros do this already?
A bit of apples vs. oranges now…even a more upright position on a gravel bike will be more aero than a hardtail. Whether you can achieve an “optimized” hoods position or not will just enhance the aero advantage (even if it is for shorter periods).
Yes, but it is a bit of a pain…the higher stack of a MTB can make achieving a similar position a challenge. See what Keegan had to do this year at Leadville…
Now that is an extreme example as most of us likely have a bit more crossover between the two geos, but there are other compromises, as well (size of chainring, etc)
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The best racing gravel bike of 2024 has been around since it’s redesign in 2022, the Giant Revolt. You can run 2.2" tires as a 2x, downtube storage and integrated cables with the 2025 model if that’s your thing.
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2025 not out until may 25 as frameset =[
So what’s the catch?
no udh 
(if you care about that)
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It’s Ugly
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The main issue with drop bar hardtails is the aerodynamics of the front fork. Most of my drop bar hardtail racing has been in events that are essentially ITTs and with limited pack riding/racing. The few road-race style gravel events I’ve done seem to indicate significant drag, even with a 60mm fork.
There doesn’t seem to be any wind tunnel data available to evaluate. I suspect the increased drag easily outweighs the impedance benefits of the wider tires.
There are courses that warrant 2.2 tires, but do not warrant a suspension fork, etc. Going from gravel bike to hardtail is a bigger step in both technical terms as well as ride feel terms than many people want to admit or perhaps are aware of.
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Revolt doesn’t have a race geo though, for size ML/56 it’s shorter and taller than Checkmate or Grail for example - bad for aero, good for chunky trails.
Any bike can be raced of course and Giant and Santa Cruz riders do pretty well doing actual racing in GP. And probably sizing down to work around the geo to get more aero.
So just strictly speaking - it’s probably not in the top 10 race bikes.
I like my Revolt (2020’ish I think it is) and I’d probably get another one if/when I decide to get a new gravel bike. Lotta bang for the buck. I do have it slammed and probably will throw on a -10 120 this winter. Are there more ‘racy’ options? Probably but it does ride well. I’d consider going down a size but this one does fit well.
I think the “race geo” concept applied to gravel bikes doesn’t make much sense given the range of parcours and equipment.