Meanwhile - Dutch beachracing champ (and DK200 2022 winner)'s bike
Dry sand without reachable hardback underneath, you just need a lot of tire. Knobs help to paddle if you’re spinning your tire, but this isn’t a practical technique on a bike and doesn’t work for turning.
Worth noting that GravelKing tires are pretty old school…some of the OG gravel tires out there.
I’m not certain they reflect the best tire designs in today’s gravel market (and as noted, they certainly don’t if you are riding behind someone with them!!)
What tires are those? Schwalbe g one? Which have tread and are not slick?
“The G-One Speed uses a small circular nub tread profile that’s tightly spaced and rolls very well on the road. The nubs get progressively taller as they reach the edges to enhance cornering grip off road”
…??
I ran the SK+ in the Unbound 100 last year. No punctures, which was job 1, but really question the value of the micro knobs to do much more than blast the down tube with tiny pebbles & grit. I’m almost 99% sure I’ll be on SS+ this year.
It’s more a texture that wears off almost instantly. i have a set right next to me. They have smaller dimples than my Gp5000 tires.
Why anyone listens to this clown is beyond me
Not trying to be pedantic but since grains of sand are so small I’d imagine all those treads could provide a significant amount of reaction force in the direction of travel compared to a completely slick tire.
Maybe the tires cost 50% more than competing tires because of the labor involved in shaving down those side knobs.
I read his aero study. He used 15 and 30 second tests. WTF can you tell from a 15 second test?
What duration do you consider acceptable?
AFAIK, these shorter sample rates are relatively common in this type of testing. It’s about getting drag values in a state and comparing to others in that same set of variables.
Those short times are extrapolated into longer ranges like 40k or longer to relate more to specific event distances as needed.
Extrapolating is fine but I don’t see how his measurement could be precise enough when taking 15 and 30 second samples.
It’s been nearly 10 years since I was in the WinTunnel at Spesh for my testing, but they did some short window of testing as well. It was no longer than 1 minute per position between our test cases. Their equipment at least, is sensitive enough to get force/drag data in that duration, to which they dump right into their formula to get the longer projections.
I have no idea what RH does, but this process can and does work in this basic small measure to large estimation process for whatever equipment and setup Spesh made. I can only presume other tunnels take a similar approach.
Indeed, you only need sufficient time for any transient flow behaviour to have stabilised. If this happens within that short a duration, then you have your test condition.
As working section size or flow velocity gets larger, the energy costs can become sizeable so you don’t want to run any longer than necessary. I chatted to a researcher at university working on transonic flows, and for that wind tunnel at that speed, you’d get a useful test window of well under a second!
I agree with the article. I think some are losing a central point. Jan is not saying knobs are not beneficial, he is saying SIDE knobs are not beneficial. If knobs help with all around traction, use them. I do this in the winter riding in the mountains because all the gravel roads are mud and snow strewn. In the summer I have only used slicks properly aired for the conditions. If I can stand on the pedals and accelerate with my slicks, I run the slicks. If I can stand and accelerate only with knobs then I run my knobby tires. I have run side knobs in the past and they feel terrible when they “hook up” and cause as many issues as they prevent in my experience. I have found high volume file treads/slicks to be better in traction and better all around when riding gravel but I live in the PNW where it is dry when I do my gravel rides. On the rare occasion I do a winter gravel ride in the hills, I will consider knobbies if the roads are muddy. I have multiple sets of semi slicks (side knobs) hanging in the garage I never use anymore because they are slow for slicks and don’t help when I need it.
This is really interesting context — thank you for sharing. I knew RH has done wind tunnel testing in the past and it’s interesting to see them using similar timeframes for the tire testing!
They are measuring CDa right? It doesn’t take an hour of wind tunnel time to test for that.
This is the wider tires are not slower article:
First, Herse is trying to sell his stuff. His testing methods are not super scientific. I just take what he writes with a grain of salt. He states contradictory info like on one hand ‘wider tires are faster’ than then ‘wider tires are NOT slower’. He completely discounts the more rigorous work of BRR.
I have a set of GK SS, GK SK+, Pirelli Cinturato Gravel M, and Pathfinder Pro in both 38 and 42. So I can now overthink it and guarantee that I have wrong tire for Unbound! 
Just close your eyes and grab a random set from the bin. Introduce a little chaos into your life! 
So I read the article. The main argument seems to be that most people don’t lean the bike enough in gravel corners. I don’t know how you ride your bikes, but I (still beginner) lean the bike quite a lot (like a MTB, bike steeper than the body). This gives me more stability and body weight is deeper, also more weight on front tire.
Of course it depends on the length of the corner. In long enough corners my knobs (pathfinder pro and some newer schwalbe tires) catch the dirt/gravel. I see that they are dirty after riding.
The whole article however reads a bit like a marketing text. And they also sell tires with knobs.
This is why I loathe gravel. Just stick a pair of conti 5000’s on the road and be done with it.
