That’s my point - if a static value is used for CdA, then the aerodynamic differences between tyres are not being measured, so a faster tyre may be faster for both rolling resistance and aerodynamic reasons…. so he is not testing rolling resistance in isolation, he’s testing speed, with the ‘fair enough’ caveat that rolling resistance far outweighs aerodynamics for determining a tyre’s speed.
To isolate for rolling resistance, the CdA would need to be different for every tyre tested (which is clearly impractical).
“is not testing rolling resistance in isolation, he’s testing speed”
Ah, I think I see your point. Which is valid, there’s not clean isolation of rolling resistance vs. air resistance. Just some isolation due to selection of what’s changed between tests. And I’d expect given all other equipment and body position the same between runs, the difference in aero between similar-width tires at gravel speeds is quite low. Meaning the Crr isolation would be reasonably solid.
And it’s not really “testing speed” in the sense that velocity is only used indirectly in virtual elevation calculation. It’s not like rolldown testing or velodrome testing at constant power where the fastest run wins. Sometimes in Chung testing the slowest run may end up having the lowest Crr (or CdA) estimate.
Oh, I’m measuring the aero differences between them too… kinda part of the protocol to get the diff aero values to solve really clean for rolling resistance.
It’s not super impractical, but there is some extra care needed while testing to get it done. @Robert_Chung discusses this in his white paper… example here:
Ah good to know, thanks for the correction. In layman’s terms, as long as speed is varied enough across the run, you can tell the difference in CdA because the rolling resistance is constant?
yeah pretty much. Both should be constant, so then the power and speed variation mainly on uphill parts helps to find a unique pair of both values that matches the repeated efforts to the actual elevation profile (1 meter DEM in tiff files)
this is a good example from a test I did a few weeks ago.
If RH is a ‘cult’ with no basis in performance fact, why do so many top athletes choose his product - and then win/place highly on them? I’m guessing Sofiane Sehili, Lael Wilcox, Ted King and Brennan Wertz (current US gravel champ) all have their own reasons for riding RH.
Observing facts (a boatload of wins and placings), and in the absence of any explanation to the contrary, maybe the truth is they’re really good tyres all round?
Or maybe the lesson is that all the minutiae of testing using whatever method covered in the thread above doesn’t amount to a hill of beans in the real world of all-day riding/racing, and people placing their faith in said tests to declare a ‘winner’ are fooling themselves?
Not to reopen the can of worms, but my only thought on this is that I don’t personally think using sponsored athletes winning races is a good example for judging performance in this case - I would see this mainly as a source of income first, performance second (not to say that athletes would choose bad equipment for money’s sake but if two options are good enough but one of them pays your bills then it’s a no brainer).
I’m not disparaging RH or anything but it’s not like any of those athletes (or any athletes for that matter) are going out and repeating race routes on competitor equipment - I’m not going to say that Pogi only wins because of the Colnago he’s sitting on.
That the tires are the best because sponsored pros frequently win on them is an arguable point, but it is a valid point that contributes to the discussion. It’s making that same point seven times in the same thread that make people feel like there’s something cult-like about fans of the tire.
I don’t mean this as an attack. You clearly believe in the qualities of this tire and want others to benefit from them. I feel like you should know why the message isn’t being received the way you’d like.
My raising it was to get an answer that made sense. Scrolling back I think you’re the first person to acknowledge that frequent pro wins is a valid point in the discussion (thanks). Maybe that will help people looking for a better tyre option to look beyond charts and marketing claims (yes, including RH’s own test results) to what happens in the real world.
Again, I’ve already conceded waaaay back that there’s no ‘best’, they just happen to work for me, where and how I ride. YMMV.
p.s. What’s really funny is people assume RH has lots of money - any money - to pay riders to use their stuff.
I’m subscribed to their blog, so when they posted this in mid-April, I assumed that Rene Herse sponsors the Rene Herse Racing Team. Did I miss something? If it was an April Fool’s joke, count me fooled!
If you read it, it wasn’t a ‘business decision’. He wasn’t looking for a team to spend money on. The first four paras cover it pretty succinctly. They don’t pay people to use their stuff because they don’t have to. This team were already using RH, and when another sponsor pulled out, RH stepped up because he liked them and they had been kind to him. I doubt other brands - owned by private equity, subsidiaries of much bigger orgs etc - would or could do likewise. I may be doing them a disservice, but I doubt it . Nuanced, sure.
Sponsorship doesn’t necessarily have to be paying a salary, free or discounted equipment goes a long way too. If you’re an amateur or privateer I’m sure saving 150-200 on a pair of tyres when you need a change helps out, if you’re getting them for free. I don’t doubt that Jan and the team get on but I doubt they’re putting his brand over their jerseys for nothing in return. Lots of amateurs sponsored by a local shop that just get a discount or some free kit etc.
As an aside seeing as she’s come up a few times as an example, Lael Wilcox is seemingly a specialized rider now going by her sponsors page and bike setup - might have to buy some of their tyres to get me around the world and come 4th in unbound
Thanks heaps for that John. I believe the winner Cameron Jones was running the slicker variant of his two tires on the front too which was an uncommon choice apparently. There is a bit of a interview with him on Payson McElveen’s podcast. Actually, looks like there is another new one as well.
Just so we’re crystal clear, unless you’ve got evidence to the contrary, is it fair to assume that Rene Herse is contributing financially (in addition to provision of tyres) to the Rene Herse Gravel Team (whether or not it was a sensible business decision to do so), Ted King, Sofiane Sehili and Brennan Wertz? (As noted, Lael Wilcox now seems to be all-in with Specialized).
That does not mean that those riders aren’t happy with RH tyres, or couldn’t have sought out alternative sponsors. And there may be other riders of a similar calibre riding RH tyres that they have purchased with their own funds (or received free but with no further financial contribution from RH).
Maybe I’m wrong about that. But assuming I’m not, it does feel a bit disingenuous to claim RH can’t/doesn’t pay riders, even if their marketing budget is orders of magnitudes smaller than some of the big brands.
RH lists King, Sehili and Wertz as “very much part of our team”. I think it is safe to assume that they are sponsored riders.
before this conversation, I had never heard of Sehili before. Ted King is well past his prime and not winning any meaningful races anymore. Wertz did win the gravel natty champs last year and SBT GRVL this year on RH tires.
As noted earlier, Keegan won some of the biggest gravel races in the country on some of the slowest possible tires (Maxxiss Reavers). Winning does not necessarily equate to fast (or even good) tires. I don’t give much credence to what pros are riding except for when they are free to choose their components and test options to arrive at a result. Even then, I’ll pay close attention to their reasoning (i.e. did they make a certain HB choice for comfort vs. aero, etc)
. Nuanced, sure.
