Yeah, that one is kinda funny. Here is one that might surprise some folks:
I tested (Chung method) the not fast (pure grip) race king 29 x 2.0 on pavement last night… almost identical rolling resistance to 700 x 42 pathfinder pro. Both done at pressures used for gravel.
This is the Drew Dillman argument; a gravel tire would naturally be faster where there are little to no suspension losses because it is narrower, higher pressure, and has less aggressive tread. Whereas the fastest XC tires are slower because they are wider, softer, with more aggressive tread.
What was recently recognized by DJ (and others) was that the fastest XC tires appeared to have more supple casings which means less hysteresis and impedance losses than the typical gravel racing tires - on pavement. These lower losses become marginally more beneficial at an increasing rate as the surface crr increases and suspension losses increase.
As you said, there has to be some mechanism that makes the TB slow on pavement, other than aero. Hysteresis, tread pattern, suspension; mechanisms we already know and can identify and test. It’s possible there’s some factor that has not been clearly identified as an intangible, but it would still be present in the testing and the scale isn’t there.
I also think the aerodynamic penalties are if not overstated, too broadly applied. There are very few aero-tests of XC tires on modern gravel or event MTB carbon rims. We know there might be something more than what we’ve seen so far after the results DJ had wind tunnel testing the 2.2 Race King on deep rims.
On the topic of gravel tires on XCC being discussed a few posts above, I’d just like to mention that I know from a few reliable sources that what some of the teams are looking for is lower weight rather that rolling resistance. Some of the Short Track courses are more manicured than many gravel races, so reducing inertia can be worth optimizing for while trading off some volume
Yeah not much on it.
I’ve done it back and forth with Reserve shallows v Hunt Limitless. Good aero results for both 40 mm caracal race and 52 mm thunder Burt’s on the Hunts.
On Payson’s podcast, he gets into a tire width discussion with Alexey for a bit. Payson basically saying wider is almost always better and Alexey giving a much more measured viewpoint. Probably no coincidence that Payson is sponsored by Allied (who just launched a bike that supports MTB tires) and Alexey rides for Enve (I think officially supports up to 50?). And a good tangent besides the typical “depends on course” was a discussion on “who” is better suited for wider vs. narrower. Payson made the point that wider is better for the “typical joe” at these events and I tend to agree with that. More comfort is usually going to translate to a better day even if there are situations where speed vs. watts is sacrificed. And that also had me thinking about how much speed plays a role in comfort. There are a lot of courses that I go pre-ride and it feels like a complete beat down going 15-17mph, but then you get to race day and you kind of fly over some of that chunk and it doesn’t feel as rough or sketchy. For slower/amateur riders, there are probably bigger reasons besides speed vs. watts that someone might want to run a larger tire.
Thijs Zonneveld (Dutch Maffia) did this last year. He switched between faster tires and tires with more protection or more thread for sections of the course. He was with the winning break with Haga and Lachlan but flatted from that group.
Will be the kiss of death for my next race now, but I got round the Gralloch on 2.25 Thunder Burt front and 2.1 Thunder Burt rear without puncturing. Running inserts. Think I was probably running them at 20psi.
Well now I’m at 3 I know of who punctured and 3 who didn’t.
Lower pressures definitely seemed to help.
Interesting to hear @gloscherrybomb did it on Thundero’s, as that was my second choice, albeit in the 44 non-HD version. I do like those tyres! 
Which casing TBs? I tried the Race Skin variant years ago and I slashed it in mild terrain the first week, but dang they were fast.
I’ve been running the Super Race 2.25 TBs on G23s without inserts front and rear locally in Ohio for the past month or so, and so far holding up well. Puntures typically are not as big an issue here compared to Arkansas or Kansas but still a good sign they are holding up.
The Race variant as that was all that was available at any sort of reasonable price
Oh brother… Think MTB tyres are fastest on gravel? Think again.
Has John K. ever tested gravel suspension or weighed in on this? My gut tells me this has already been litigated. Clearly when it gets really rough it’s going to help. Class I/II seems unlikely, but I am willing to be convinced.
In my experience, for the local “gravel” that I ride the most, a hard tail mtb would objectively be a faster choice for most of it. However it’s more fun to under bike lol.
For the course I think it’s again very dependent, some of them would be quicker with suspension but others have enough champagne gravel or road that it becomes harder to know what would be best for an overall quickest time.
I get a weird buzz from every new piece of evidence that that makes the ‘it depends’ answer even more ‘it depends’.
Without being a physics major it does kinda make sense to me intuitively. Smaller contact patch so less friction but still mitigating vibration and suspension losses. The weight and aero penalties then need to be considered based on course and likely pack characteristics.
Yeah that was my first thought (actually his chat with DJ which may or may not be the same thing?) I didn’t actually click on this link but I’m guessing they’re talking same principles.
Flight Attendant seems like the other piece of the puzzle that makes the next gen of suspended race bikes really work IMO.
Aero-faired FA 100mm full-sus at about the weight of a current mid-tier rigid Ti gravel bike would be my guess for the pinnacle of that generation of technology (assuming no unexpected tech developments before we get there, which of course there will be). Tires at 45-50mm WAM with rims to match.
Two things Re Gravel tire and suspension fork,
this may be true for the front, but what happens for the back tire?
May be faster in a straight line, but where i live, i gots to corner fast too. Surely a mtb tire corners better
Actually, never mind, everyone go back to gravel tires please, that would be way cool for me in my races
This has me thinking about the new Diverge. I know ppl talk shit about futureshock but maybe that little suspension and 50mm Tracers or 2.2 MTBs are actually quite a bit faster than these aero gravel bikes that barley clear 45mm…
