ericM40-44 wrote:
Damon, I don't remember for sure, and don't want to name names but I think that I remember Jordan Rapp saying something about it here when he was a Zipp athlete. I think it was more an accident that they found the 23mm GP4000s to be faster, not by design, so b) in your post. But I also wonder, because they have a graph that shows the 22mm Attack slightly faster still, in line with what you would expect a narrower tire to be. Maybe it was just an urban myth that got spread around ST.
I always wondered about the claims of a 23mm GP4000s as it's a bit wider than my Firecrest 808s. Luckily I have a 22mm Attack on par with the Crr of a 23mm SS or 24mm Turbo Cotton, 24mm Force, etc. and so I run that up front. I always considered the 20mm SS too narrow for my wheels and also not as fast rolling as my 22mm Attack.
that said, I brought that up as an example of the industry's race to be the fastest at 20 degrees of yaw and 18mph, for *individual* components, which muddies the water with what we're really after as lower yaw athletes:
what's the fastest wheel tire combo for our bikes?
What is the optimized tire for our wheel?
Is the HED 3 "watts to spin" myth really true or not?
Why does everyone report great things from the H3 when all competitors and even HED in some graphs have it slower?
If the H3 is a good wheel, does the H3+ additional width allow for a better rolling tire and what are the aero gains/penalties of the wider rim?
damon_rinard wrote:
ericM40-44 wrote:
Zipp told us that the GP4000s 23mm is the fastest tire for their wheel
I'm curious if someone can point to a source for that claim.
I recall the rim was reportedly
(1) optimized for a 23C tire, but I was looking for and never saw a claim that
(b) a 23C tire was optimal for that rim.
Two statements with similar, but not quite the same, meaning.
In my experience testing tires and rims (in CFD and wind tunnel testing), the most aero tire is usually narrower than the rim it's on, and the most aero rim is usually wider than the tire mounted on it.
In fact HED's patent puts numbers on this effect.
Cheers,
Damon
The wheel was designed around use of a 23mm tire, but that doesn't necessarily mean that a 23mm tire was fastest. It's still really hard to get around the speed of narrowness (aerodynamically). In this case, it was more issues of total fit. Basically, trying to minimize the penalty of using a wider tire. The goal, of course, was to design a rim for tires that people actually use. And to try to shrink the aero hit so that Crr gains more than made up for it.
Yes, the GP4000S was a "fluke" by all accounts. Maybe Continental knew what they were doing, but maybe not. There's also some importance that different rims do better with different tires. I.e., the GP4000S was a really good match for the Firecrest shape. But that doesn't mean it was/is THE fastest tire (aerodynamically) for ALL wheels.
At the time the wheels were benchmarked, I *recall* (perhaps incorrectly) that the 22mm attack (and some of the other newer Conti tires) hadn't yet been upgraded to the Black Chili rubber, so they were fast aero-wise but bad for Crr. That's hard for Zipp to update with speed, because Continental is a separate company.
Anyway, I think the fastest - aero tire - is still the narrowest (though maybe not if you are talking SUPER narrow tires like 18 or 19mm where the lip would be really pronounced; but nobody really seems to run those anymore anyway...). In terms of practical tires, the 22mm Attack seems to be the fastest, but of course it is a (relatively) narrow tire, though it'll be wider on a wider rim than it would be on a narrower rim.
All your other questions are good questions that I don't have much to add except, "it depends." And, in the case of the H3, it *seems* like the "it depends" depends on MORE variables than other wheels. Like, the variance on that wheel is quite high depending on other stuff...
"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp