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Oct 12, 2022

In this week’s episode, Randall has Josh Poertner on to talk aerodynamics. In a wide-ranging conversation, the two touch upon Josh’s time as Technical Director at Zipp, involvement in the development of computational models for rotating wheels, early collaboration with Cervelo founders Phil White and Gerard Vroomen, founding and leadership of the product brand Silca and The Marginal Gains Podcast, and ongoing consulting work with elite athletes and teams.

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Marginal Gains Podcast

Episode Sponsor: Logos Components 

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Automated Transcription, please excuse the typos:

Silca - Josh Poertner

[00:00:00] Craig Dalton: Hello, and welcome to the gravel ride podcast, where we go deep on the sport of gravel cycling through in-depth interviews with product designers, event organizers and athletes. Who are pioneering the sport

I'm your host, Craig Dalton, a lifelong cyclist who discovered gravel cycling back in 2016 and made all the mistakes you don't need to make. I approach each episode as a beginner down, unlock all the knowledge you need to become a great gravel cyclist.

This week on the show, I'm handing the microphone back to my co-host Randall Jacobs.

Who's got Josh Portner, the CEO of Silka on the shout out a wide range in conversation about the sport and high performance. Many of you may be familiar with the storied Silka brand. It's been around for close to a hundred years. But josh took over back in 2013 with a mission of merging the highest quality materials and craftsmanship with cutting edge design and manufacturing

When you visit the Silca website, you notice a tagline, the pursuit of perfection, never settling, always improving. And I think that embodies how Josh approaches the sport. . So I'm excited to pass you over to Randall to dig into this conversation. Before we jump in i want to thank this week sponsor logos components

Yeah, I've been itching to get back on a set of six 50 B wheels, and I've been waiting for my logo's components, wheels to arrive. They literally just arrived last night and I'm super stoked. But yet disappointed because I have to go away for the weekend and I won't be able to actually ride them

until sometime next week. I chose the Atara six 50 B model. As you know, I'm sort of big on the big tires, big fun philosophy. So I've been eager on my unicorn, which I've been riding on a 700 SEASET for a while now. To get into the six 50 bees again and see what a six 50 by 50 combined with that rock shock fork is going to yield for me on the trails here in Marin. You guys may remember.

Me sitting down with Randall, talking about what makes a great gravel wheel set and everything that went into these logos component wheels. I encourage you to go back to that conversation because whether or not the logo's wheel set is for you or not. I think Randall does an excellent job of teasing out.

All the various considerations. You should be having when considering buying a gravel wheelset,

It is no small expense when getting into a carbon wheel set, but the team at logos has endeavored with their direct consumer model. Uh, to make it as affordable as possible and make them as durable and high performing as anything out there on the market. I written wheels designed by Randall for the last three years. So I'm super excited.

To see his latest vision come to fruition. With these new wheels and I'll have them underneath me soon enough. I encourage you to check them Randall's also an active member of the ridership community. So if you have questions for him, feel free to join us over there at the ridership and connect with other riders. I seen people paying that their wheels have arrived so you can get some real, real people answering your questions.

About whether they're enjoying the wheelset and how they perform, et cetera. And I'll have more on this in future additions.

At this point. I'm going to hand the microphone over to Randall. And i hope you enjoy this conversation with josh

[00:03:30] Randall: Josh Portner, thank you for joining us on the podcast. This is a conversation I've been looking forward to for quite some time. Some deep bike nerdy is probably about to ensue, so, uh, let's dive, let's hope. Dive right into it.

[00:03:43] Josh: Well, thank you for having me.

Always, always up for some deep bike. Nerdy. I like that.

[00:03:49] Randall: So a number of our listeners will already know who you are, but just give folks a high level summary of what you do now.

[00:03:55] Josh: Oh gosh. So I own Silca, um, or I own Arrow Mind, which, uh, owns the Silca brand and trademark, um, and, and all that that entails.

And then we also have a, uh, we own Marginal Gains, which is a podcast and a YouTube channel. And, um, Yeah, our goal is to, a mind works with a lot of pro riders, pro teams, world tour teams. Um, you know, we do everything, Excuse me. We do everything from, you know, performance consulting, uh, modeling, uh, you know, setting up our record attempts for people or, or helping them design our record attempts.

Um, you know, we do tire pressure work with pros. We do equipment choices for teams. We think some of the most interesting stuff we do, um, is around where like, uh, teams or national federations don't trust the equipment they're getting from somebody. And they'll come to us and say, you know, the, you know, bike brand X says that this does this, and our writers don't think so.

Can you tell us what's true? And. We'll find a way to make that happen. So we, we've had some pretty interesting ones of those with, uh, particularly around the Olympics with the national federations. You know, no, nobody wants to have another Under Armor speeds skating suit, uh, situation, , right? Where all the, all the athletes think something is true and therefore it becomes true and, and nobody knows.

And so, um, you know, so we do a lot of that. Arrow mind does that, essentially. And so that's a lot of the performance work I was doing in my old world. I was technical director at ZIP for almost 15 years. Um, and, and then Silca is the product arm of the company. Uh, that's probably how, you know, most people know us.

You know, we make pumps and tools and, and, but we also make a lot of crazy things that people look at me and go, Oh, where the hell did that come from? Well, that probably came from some project or another. We did it in the Arrow Mind side of the business, Um mm-hmm. . So that's how we've gotten into sealants and lubricants and 3D printing and, and all sorts of other craziness.

Right? That's sort of how the one flows into the other. And then, you know, Marginal Gains is a podcast and, and YouTube channel where we talk about it all and, and we, we typically with a, a team or a company have like a two year. Secrecy period on a technology. And then after that we can do something with it and, and talk about it and tell the story.

So, you know, it's always, it's always fun to go through those periods where like, Oh, thank God we can talk about that now, . Cause you know, we're talking about it internally all the time. And, and you're like, Oh, can we put that in the podcast? I don't know. So, so that, that's what I do now. We, I, I play with bikes basically.

[00:06:34] Randall: Very, very cool. And, um, when you talk about the consulting work you do, is this kind of full stack performance consulting, is it very a focused, is it all technical sides, including say, like bearing drag or, or things like this? Is it, um, obviously positioning falls into Arrow Nutrition. Like where, where do you, ooh, where does your domain physiology start?

[00:06:57] Josh: And I draw the line at physiology, you know, there's a whole, there, there are people who are, are like my equivalent in that world. And, and my God, I can never even dream to. You know, clean their shoes. So, um, no, you, you need someone to talk physiology, you know, And I'll, I'll pull my phone out and we'll call Allen Li or somebody, you know, Yeah.

With a bunch of contacts. But, uh, you know, Alan's one of my favorite go-tos for things like that and be like, Oh dude, I've been over my head help . You know,

[00:07:21] Randall: he, he's, um, he's actually been on the pod before, but Craig interviewed him, so I might bring him on in the future to do, you know, my, my more kind of nerdy type of interview.

Alan's great. Yeah, no,

[00:07:31] Josh: he's, he's a lovely guy. He's a lovely guy. And, and I just love, I mean, he, you know, like I find myself pretty quickly sometimes getting into places where people's eyes just glaze over, like, what the hell is this guy talking about? And, you know, I love that Alan can do that to me in about 30 seconds, you know, we're talking about the stuff that he does.

You're like, Oh, whoa, shit, way over my head way. I, I didn't even recognize the last four words that you used in that sentence, . And, uh, so it's, it's awesome to be able to be surrounded by people with that. But no, you know, we. The stuff that they come to us for. I mean, you know, when I left sip and started soak, of course everybody and their brother, you know, came and said, Oh, design us a wheel.

I'm like, well, like I can't do that for a couple years. But also I'm kind of just done with that, you know, like I've lived that life. I, you know, it, it was fun. But, you know, we, we continually updated wheels for 15 years, but it, it really is kinda like doing the same thing over and over again, you know? And, and so it just wasn't fun for me.

So, you know, they'll come and say, um, you know, help us design this cockpit, or we, we do a lot of, with our, our in-house, uh, 3D titanium printing, we do a lot of custom cockpits for, uh, teams, riders, things like that. You know, where we laser scan the rider, get the position, lock that down to the wind tunnel, design the part, 3D print it, um, you know, stuff like that, that, that's really exciting.

We, we'd get a lot of, you know what, um, You know, help us optimize for this time trial at the tour or the Olympics or whatever, where, you know, what tires should we run and we can, we have systems and tools and, and spreadsheets and a million other things that we can, um, Yeah. Help, help them determine. And then a lot of times we, you know, we get companies coming to us, um, really just wanting to know, like, you know, if, like, which of their sponsor products should they use and when should they go off sponsor?

You know, you'll see that a lot at like, the tour where, excuse me. Um, you know, like they, they ride the sponsor correct product, you know, 98% of the time, and then they're gonna sneak it in here or there when it's really critical. So, you know, what, what are those really critical points? And then, you know, if, if they're gonna risk getting in trouble or outright get in trouble, like it needs to be worth it, right?

And so they might come to us with like, okay, you know, we need. I need a time trial tire for this rider for this day. You know, what should we do? And, and we'll help him with that. But yeah, you know, if you, if you were a, a brand, uh, or a world tour team there, or approach our athlete that wanted to go to the win tunnel, you know, you might pay us to come along.

Um, a lot of what I do too is kind of fun is just act as like a fly on the wall in these team to sponsor interactions. You know, I think I was probably at half a dozen wind tunnel tests last year where I really had pretty much nothing to contribute other than being the neutral third party in the room, um mm-hmm.

you know, so that everybody was comfortable that everybody was. Comfortable .

[00:10:26] Randall: Well, I would imagine there's a mix of the, uh, the political, if you're talking about, you know, what should be using our own sponsors gear versus slipping something else in all the way to, um, balancing the competing goals of say, like comfort and pure power output on the bike versus aerodynamics.

Um, if you're talking about a time trial position. Yeah.

[00:10:47] Josh: Oh yeah, for sure. And, and I think even down to, you know, and I think as much as we love to talk science and testing and, and try to be as scientific as possible, I mean, this stuff is really, it's emotionally hard. It's politically hard. It's, you know, companies will bring new equipment in, they're with their engineers.

I mean, those guys and girls want that stuff to work so bad. And you know, sometimes you just see things coming out where, Oh yeah, that's clearly faster. And you're like, Well, actually, the way I would interpret that is it's probably about. The same, um, or mm-hmm. , you know, let's, let's rerun that test or, um, you know, it's always, I don't know, it, it, they, they like, people like to get themselves in these loops where, you know, Oh, we did this and it's 10 seconds faster and it's that, And I feel like back in the, you know, when I was with zip, we did this a lot during the Lance Armstrong area and he was writing our disc and, and we were coming in as consultants for the first probably five tours or whatever.

And um, you know, every wind tunnel test you'd get to the end and they would have this chart that's like, we just made him 90 seconds faster. And it's like, look guys, that. There is no 90 seconds faster. I mean, you know? Mm-hmm. like, like that is not gonna happen. You know, you, you just did a whole bunch of stuff that's not sustainable that he can't hold his head like that.

Mm-hmm. that helmet tails gonna come off the back, you know, I mean, cuz he, people do things like, Oh, oh, the helmet tail moved, rerun. You're like, Yep guys, when you ride in the real world, like the tail's gonna move. Like you don't, you know, people like to, they select data, um, without even realize they're selecting data.

And so, you know, it is, it's just good always to have a third party in the room. Um, you know, it's kinda like funny story, you know, back to, you know, my zip days, how Firecrest came about, you know, Firecrest was literally the name of the prototype that, that kind of blew all of our minds. And the reason the prototypes had weird bird names was that we had to double blind them across engineers because you just didn't want anybody.

Kind of, you know, having an effect on their product, right? I mean, we all, you know, we all fall in love with our children, right? . And, and in this world, like you, you can't love your children. Um, and you have to be willing to kill them when they're not good. And, um, you know, we would do this double blind thing where we would like assign them all a number and then we would assign bird name, these bird names a number, and then we would randomize it and then they would get all put up.

And then nobody really knew whose idea was what, when you were in the tunnel. Um, that's necessary, right? Cause you're, you know, you can be your own worst enemy at that stuff. I think we've, you know, we've all been guilty of that a time or two in our lives. But, uh, you see it all the time, particularly in these performance, um, improvement coaching type things where, you know, people just wanna will something into existence even when it's not.


[00:13:38] Randall: Well, and I can see, um, you know, the marketing oftentimes has it much more, uh, presented, much more like a, you know, this is just, it's physics. It's more, it's more exact, it's more, um, it's more controlled. And, um, there are competing variables, particularly when you have, you know, a monkey in the middle.

You have to, this, this, you know, this animal needs to be comfortable. This animal needs to be fueled, This animal needs to be able to control this machine through a varied environment. And that varied environment may be varying in real time if weather changes or things like this. Um, and so there's just all these competing interests.

And so when you see, you know, I often laugh at like, You add up all the different arrow benefits that, you know, different companies claim for components and you should be doing. Right. Right. You know, you might be looking at, um, uh, relativistic effects potentially at some of the speeds you'd be able to achieve.

Uh, Jen, just like how, how many watts can be saved. Totally. Being a little bit facetious there.

[00:14:37] Josh: Yeah. No, no, it's totally true. I mean, and I still have this photo somewhere, I think I even showed it a couple years ago on social media. But as this, this really great photo that I love that ended up, um, on the wall at the Texas A and Wind tunnel, but it's me with next to Lance Armstrong, um, in the, what became the Nike Swift spin suit, um, that had been flown down there from, you know, Seattle.

And it's, uh, oh God, the guy in from his book college or whatever he calls him, and then a guy from Nike, so it's the four of us. And I'm kind of standing there like doing, you know, like pointing at something on his back and it, like, a college student took it for the school newspaper and then they had him autograph it and it ended up on the wall.

And so like, Oh, that's me. You know, it's kind of funny. But, but the real story there was that suit, you know, they were paying like 3000 bucks a meter for this suit. They'd been putting it on a mannequin in the tunnel. I mean, it was gonna save three minutes per 40 k. And you're just sitting like going, guys, like, I, I mean, just quick doing the math, like three minutes for Lance Armstrong, you know, like the guys already, That's not possible.

And, and of course we get it. We put it on him. Um, the whole thing, you know, it, it's, it's cool, it's fancy, it was very red and it does nothing. I mean, it literally, we were, and the Nike people are there and they're like, Oh, that's not possible. It, it can't do nothing like whole. Let's run it again. Okay. Now get 'em out of it.

Put 'em in the normal suit. Run that one. You're like, it, it just doesn't do anything. And, and they just kept going. Well run it again. Well do this. Let's, let's close pin it up. Let's tighten it. Let's, do, you know, I mean, I bet we, we lost two hours trying to make that stupid thing look like it would do anything.

You know, And again, it's, it's just people being people and we've all done it. But

[00:16:21] Randall: I hear like something of stages, of, stages of grief. Like, you have your baby and like first it's denial, and then you, then you have bargaining. Yeah. Yes. Put so much into this. Yeah, that's exactly,

[00:16:32] Josh: that is exactly what it is.

And, and you know, the, the crazy reality with that one was, you know, three months later at the tour, they launched it anyway, and they said it saved three minutes and he , you know mm-hmm. . And we, we. It, you know, I just had to laugh. I mean, I remember, you know him, you know, winning whatever one of the time, trials by like a minute and like going, No.

So Nike's essentially saying he would've lost that time trial by two minutes had it not been, had he not been wearing that suit. Come on guys. Um, yeah.

[00:17:00] Randall: Well, and I think that, that maybe that's, um, you know, headline number one from this interview is don't believe everything you read, especially if it's coming from a party, has a financial interest in it.

[00:17:10] Josh: That is true. That is true. Yeah. I, I, I tell don't, don't even believe yourself. Right? I mean, truly like you, you are a bad, um, a bad predictor of things and, and you're a bad feeler of things and nobody wants to admit that. Um, but it's just true. You know, that's, I've been preaching that gospel for, for years.

But, you know, I mean, 90, I, I would say 90% of the things you. That you feel when you're on your bike. Total, total crap. Um, and, and we know that cuz we, we've done blind testing with riders. I mean, like unbelievable world class rider. And if you blind them to what they're actually riding, they can't tell you almost any Yeah.

Um, you know, all that perception, but still, but the stories away, the

[00:17:56] Randall: stories we tell ourselves are powerful. There is a strong placebo effect. Oh, for sure. Uh, for sure. But it has to be acknowledged that that is the placebo. And if you actually had those beliefs about things that had genuine benefits, you would get both, You would get the actual

[00:18:11] Josh: benefits.

Yes. The, the most powerful thing in the world is a placebo that actually works. Right. , where you get, it's like a, it's a double whammy benefit. Um, and so yeah. That, that's where, you know, I mean, in a nutshell that's a lot of what, you know, I've made my career doing right, is trying to help, help sway people towards the, the, the placebos that, that actually do have a, a, a benefit for them.

[00:18:34] Randall: So this has the conversation going in a slightly different direction than I was anticipating, which I'm really enjoying. So I've been, I've been diving into this lecture series from this guy Robert Sapolsky at Stanford. It's on, um, the, uh, uh, behavioral biology, and it's looking at all the different ways in which studies go wrong.

And so there's like, you know, beliefs about something, uh, for a long period of time, you know, eminence, people in the field, uh, promulgate these, you know, these ideas. And then it's shown that, you know, the study was, was not, uh, taken, uh, done properly or what have you. And so I'm curious, let's dive more into things that go wrong in the study of aerodynamics and, um, maybe kind of the edge of, say, human performance where interfaces with aerodynamics

[00:19:17] Josh: Hmm, ooh.

Interest. So, I mean, a, a good. I would say career defining for me, example of that was, um, you know, we, from like 2009 to 2012, we were really all in on developing, uh, CFD for the, for bicycle wheels. And it, it just wasn't working right. Everybody was talking about it and showing papers, and, but I mean, it just, the reality was like the CFD just never looked like the wind tunnel.

The curve shapes were different. The data was, we're, we're talking It

[00:19:47] Randall: wasn't mid, mid

[00:19:48] Josh: nineties, right? Oh, no, Mid, mid late two thousands. Yeah. Like mid, late, late

[00:19:53] Randall: thousands. Okay. Yeah. And you're not using, you're having to develop something ground up or you're having to, uh, adapt something from Desso or, or one of these bigger

[00:20:02] Josh: vendors.

Yeah, So I think the question at the time was, you know, how do you, how do you really properly model the spinning wheel in, in flow that's also translating, right? And you look at. You know, all the CFD stuff with aircraft, um, you know, there's no rotational flow, you know, and then you look at, there's special models that people have built to look at, like, um, turbine jet, turbine engine combustion or whatever.

But those are incredibly unique. And they're also, you know, there's RO flow rotating, but in a different access and Yeah.

[00:20:36] Randall: The F1 guys perpendicular access.

[00:20:38] Josh: Yeah, exactly. Exactly. And so, and then you got the F1 guys who weren't really modeling, um, they were modeling the rotation of the wheels, but they were doing it by modeling a rotational component at the surface of the tire.

So you were, you weren't essentially like spinning the wheel, you were just saying, Oh, there's a induced rotation a about this surface. Um, which has been in the, the solvers forever. So

[00:21:02] Randall: in interesting, this is taught because the, those wheels are traveling so quickly, especially the top of the wheel. If you're doing 200 miles an hour, the top of the tire is traveling at 400.

And so you're having sign significant turbulence at that interface, right? Well,

[00:21:15] Josh: and you, you have like Magnus effect, right? You're actually getting pressure differential top to bottom, um, you know, from , the direction of the wheel spinning. And so, you know, we, we could do stuff like that pretty accurately, right?

You know, you could look at the, you know, a rotating baseball and, and predict the direction that's gonna curve. I mean, things like that were possible. But, you know, every single, and, you know, my God, I used to get, I still do occasionally, but I, I used to probably get 20 PhD papers a year from kids all over the world.

Um, you know, Oh, what do you think of my paper on, you know, CFD of bicycle wheel? And we're like, Oh, it's beautiful pictures, but your data's crap. Um, . And it just wasn't figured out. And, and in 2009, I, I met a guy, Matt, uh, Godo, who's a triathlete, but he also worked for a company called FieldView. And they had built all of the CFD automation for, uh, Red Bull F one, um, and probably half the F1 grid, but his, his big account was Red Bull.

Um, and he, I met him at Interbike and he had a paper that he was working on. He said, I think, I think I might have figured this out, but I really need to be able to like, Like, build a wind tunnel in the computer and then look at it so we can directly compare them back and forth. And, and so we, we did that.

We published a paper at the a I a, which was at MIT that year, and it went over really well and people liked it. And we published another paper the next year, um, at, at the a i A conference. And that went well. And then we got this big grant, like an $80,000 grant from Intel, um, to really tackle this problem.

Cause the, the head technologist at Intel at the time was a guy, uh, Bill Fry Rise, and one, one of the coolest guys I ever met. Um, you know, the kind of guy who, whose resume just has like a five year period that says like Los Alamos , like,

[00:23:01] Randall: okay, you're cool. You know? Yeah. Yeah. Not, not allowed to talk about it.

What do you do? Yes. Uh, yes, exactly. .


[00:23:08] Josh: uh, but he was a cyclist and he was some senior, somebody at Intel. And, and, um, And they, they gave us this money and we, we, we really went hard at this and we ended up developing a, essentially all of the little nuance details. Uh, we did it in star ccm. We post processed it in field view.

I think we processed it on like a thousand cores, which for 2010 was, you know, a lot. Right.

[00:23:33] Randall: Um, and these are, these are, um, CPUs and not GPUs for that era. Right. A lot of the stuff of that era GPUs now, right?

[00:23:40] Josh: Yeah. Yeah. I remember we, yeah, I mean, that was the beginning of, uh, that was the beginning of the cloud.

It was pretty cool, like 2008, 2009, people were still traveling. I remember at one point in that process there was discussion that like, we might have to travel, um, to, Oh God, what is it? The, the university over there in Illinois had a huge, had like a 1200 core machine and they're like, Okay, we, we might have to go there and, and buy, you know, two days of time.

And then as that was happening, cloud. Kind of the beginnings of cloud was there. And I remember we, we met a guy who had a cloud thing, and they had just been bought by Dell. And, uh, we were at a conference and he's like, Oh, no, you know, with our, our thing, What was that called? But, uh, with our thing, you, you can just do it like up in the ether.

We're like, Whoa. You had never heard of that before. Yeah. Um, it was just exciting times and, and, uh, but, but we, you know, had this great team. We pulled it together. I mean, that's really where Firecrest came from, right? It was, it was largely designed using, um, Hundreds of iterations of capes predicted to be fast, uh, using this cfd.

And, and ultimately we won. We, we became like, I think the first non university and non-governmental group to ever win a, uh, uh, innovation excellence award from the Supercomputing Society. So it was pretty cool. Salt Lake City's like this huge super computing conference and you know, it's like darpa, this and university of that.

And it was like these four guys from this bike brand and, you know, was, uh, it was a pretty cool experience. But, but in that, so that's like a huge tangent. No,

[00:25:17] Randall: no, this is, this is great. And, and just to take a, uh, stop for a second, CFD computational Fluid Dynamics software that is used to model complex multi-variate systems where there's second order effects and, you know, fluids and, and things like this.

So anyone who's not, uh, who's not with us on that, like complicated software for complicated system models, in your

[00:25:39] Josh: ideal world, it's like a wind tunnel on your laptop, right? In the, in the George Jetson's version of things. It, it's the wind tunnel on the laptop. And in the reality of things, it's kind of more like, eh, it's about as good as guessing most of the time.

But, but, but sometimes it's really good at finding certain really specific things. So I won't, uh, I won't knock it too hard, but why the thing I wanna

[00:25:59] Randall: dive in a little bit

[00:26:00] Josh: here. Oh, go ahead. Yeah, yeah. Well, let me, so let me finish the, the thing that we discovered in this process that was super cool. Um, was that once we had all of these transient, we were solving for all these transients, um, and we really started looking at not just like the, you know, the, the side force or the yaw force or you think of um, you know, the whole thing with like wheels and handling, right?

This all came out of this project cuz you could, you could predict the steering torque on the wheel, which, you know, none of the balances being used to test wheels at the time even had torque sensing, right? You had drag side force and lift, but none of them had the rotational components in there. And so that for us at first was like, oh shit, we've never thought about torque cuz we weren't measuring it.

Right? It's sort of one of those, yeah, like you've biased your study all along, but then the big one was looking at the predicted, um, data and there were all of these, uh, harmonic effects. and we kind of looked at each other and we're like, Oh my God, every wind tunnel you've ever been in, Right? The first thing everybody discusses is, you know, what's the, what's the, the time across which you're taking the data and at what frequency?

And then you're averaging that data, right? Cuz we're all after a data point. And you could look at the tunnel data and the CFD data, and when you pulled them out of their point form into their wave form, essentially you could see the harmonics kind of lined up, the frequencies match when, oh shit, we've been averaging out a really important piece of data for 30 years.

You know, this harmonic thing is big. Like what's your,

[00:27:39] Randall: your standard? So it's operating on a, it's operating on a frequency that is smaller than the sample rate. Or how

[00:27:46] Josh: was it essentially? Essentially we were just idiots and we were just, we were just time averaging the all of that out. Right. I mean, it's, you know, if you need to Okay.

Any wind tunnel you, you went to in the world and be like, Oh, well, we'll take, we here, we take data for 30 seconds at, you know, whatever, a hundred hertz, 60 hertz, 120, or whatever it is, and then we'll, we'll take an average. Oh, okay. That, that's fine. Got it. You're averaging out in there is real, um, uh, like amplitude changes, uh, largely due to vortex shedding is, as it turns out with bicycle wheels.

But a lot of that high frequency handling stuff, particularly as wheels get deep, um, , sorry, I'm in, uh, I'm in our studio, which is off of our kitchen and somebody's lunchbox just, just leapt off of the top of the

[00:28:34] Randall: refrigerator. Um, yeah, sometimes I'll have a niece or nephew come in screaming, so No worries.

Yeah. So, but,

[00:28:39] Josh: uh, but no, we, we realized there, there was a, a. About a factor of five difference in amplitude between wheels in terms of that, those oscillating effects. Right. Which typically it's just, it's generally vortex shedding. And the CFD can predict that really well, right? Where your little pressure builds up, sheds off, sets off a counter rotation that sheds off.

Um, but as a, as a cyclist, you, you feel that as the wheel, you know, kind of oscillating left to right. Um, and we, and let's, let's for 20 years, you know,

[00:29:12] Randall: Yeah. So you're just taking the, the lump, you know, 30 seconds averaged out data and saying, Okay, it gives you this amount of benefit and you're not seeing those.

Um, I mean, really what we're talking about is, uh, you know, instability that may. Or, you know, otherwise result in, in control issues on the bike. And I want to take a moment to just like, define some terms, uh, because not, you know, many of our listeners are not overly technical. Um, but uh, I think some of these concepts are easy enough to get your head around, like, so, you know, describe at a very high level you're talking about vs.

So, you know, maybe describe lader flow and flow attachments and vortices sheddings. How, how does this, how does this, uh, how can you understand this without a, a technical background?

[00:29:59] Josh: Oh, those are awesome questions. Okay. So Lader LaMer flow is kind of what you. What the, the world wants you to think of in the wind tunnel.

You see the wind tunnel picture and they've got like the, the 10 lines of smoke and they're all kind of flowing together cleanly and beautifully. That's, that's meant to, to evoke lam or flow, right. That if you were to drop a, a smoke or a particle in there, that they would all flow in lamini, you know, like sheets of paper.

Um, yeah. Uh, so, so

[00:30:29] Randall: it's going in a straight line. Smooth,

[00:30:31] Josh: controlled, Predictable, yeah. Flow. And it, it follows the contours of the thing that it's flowing against. So,

[00:30:38] Randall: so kinda like water flowing down a river sort of thing. It's not perfectly laminate, but it's all going roughly in the same direction. And there's not a lot of water

[00:30:46] Josh: in a pipe disturbance, you know, would be in a pipe better example, presumably pretty laminate, right?

And then you start to add stuff, you know, water in the river. Now you're, you're, you know, you've got a rock and now all of a sudden there's a disturbance and it starts to swirl. Um, and so you, you get into, you know, more complicated types of flow. I, I think the, the big ones, you know, for us to think about are, you know, most, so most drag that we deal with comes from, um, uh, pressure related things.

So you either have like the, the high pressure on the front of the rider, right? The wind that you're pushing into this when you stick your hand out the car window, right? The mm-hmm. the air you feel hitting your hand, you know, that's, uh, that's a pressure drag, uh, in the positive direction. And then you have the flow, the vacuum in the back.

Yeah. The flow will detach off of the object and that'll create a vacuum behind. And so that's a suction drag, um mm-hmm. . And then when you have something like vortex shedding, it's when, uh, the, the. Description I ever have for vortex sheddings. If you've ever driven an old car with, uh, like the metal antenna on the hood, you know, at some speed on the highway, that antenna starts vibrating, oscillating sideways, which is like the last thing on earth you think it would do, right?

Like your brain's like, well, it should just keep bending backwards with speed. Mm-hmm. , why is it going sideways? Well, that's that you get this thing where you have a little, uh, a little curl of flow will kind of detach more on one side than the other, and that creates a side force. Mm-hmm. . But in doing so, the suction that that has now left behind will pull a similar vortex from the opposite side.

Mm-hmm. . And that creates an opposite side force. And so you get these, see an oscillation, you get these oscillations and uh, you know, that's, it's huge in architecture and mm-hmm. , it, it's why you see so many of those super tall buildings or kind of have pyramid shapes or might have some sort of like, feature that spirals down them to, to kind of break that up.

I, I


[00:32:46] Randall: in Boston. We actually have, um, a skyscraper here that was flexing so much, the windows were popping out. This is, you know, decades ago. And, you know, it's still, you know, they have this like funnel of air that's going through there and just the nature of the shape of it and how air gets funneled in, it was causing enough torsion to, um, you know, cause window de bonding.

Um, so yeah. That's crazy. Uh, so then, you know, think applying this to the bike and particularly a wheel, um, you know, this is the biggest effect is, is presumably your front wheel where you're having this oscillation, this shift in pressure from one side to the other at a very high, high level, um, that's causing instability.

It's making it so that you may lose control of the bike. It's not predictable.

[00:33:34] Josh: Yeah. Correct. Correct. And, and the, the other thing we learned through CFD that it was doing, which is not obvious until you think about it, but so you think of the. So you might have, say it that the trailing edge of the front half of the rim, you're, you, you set up a little vortex shedding situation.

Mm-hmm. . Um, and so you've got a little side force, but it's kind of at the, the trailing edge of the rim there. Right? So it's got a little bit of leverage on your steering, but the other thing that's happening is that alternating attachment and detachment of flow, um, changing the side force, but you're a side force at an angle.

So there's a lift component, right? Which is how the drag is being reduced. And as that happens, what, what's also now changing is what we call like the center of pressure. And the center of pressure. You think of like the wheel from the side, like, like the sum, the aggregate of all the, the arrow forces on that has a center point about which it's balanced.

It's kinda like a center of mass. Um, you know, so it's, it'd be center of pressure. Well, that center of pressure when you have. Shedding happening somewhere that's now moving forwards and backwards and very

[00:34:40] Randall: rapidly

[00:34:41] Josh: as well. Potentially, Yeah. Rather rapidly. I mean, and, and when you really look, look in on it, it, the frequency actually can be quite close to, um, the, uh, speed wobble frequency, right?

Which is somewhere in that like three to four hertz range. Uh, which also happens to be really close to the frequency of human, uh, shivering, which is kind of cool's why you're more likely to, to speed wobble when you're really cold. Um,

[00:35:05] Randall: and not everyone just push will have experienced speed wobble. But if, you know, if this is basically your, you, you hit a certain resonant frequency of, of the frame based on the frames geometry, uh, the head tube angle, the what are the factors that go into that,

[00:35:20] Josh: Uh, it's top tube stiffness is big and so, yeah.

Yeah. And it's actually this speed wobble's. Interesting. It's. It starts as a residency issue, but it's really a, it's a hop bifurcation and, um, a hop B. Okay. And so, yeah. And so what you have in a hop, uh, bifurcation is you essentially have two st two stability, um, would be the best way to think of it. And you are jumping from the one to the other.

And so like, right up until that, so the

[00:35:48] Randall: system wants to be in one state or the other, but not in the middle

[00:35:51] Josh: and there's no middle. Right. And, and what's, what's so cool, like, like early in, um, uh, early in covid, you know, we were all talking about this, you know, what is it the are not value, the, you know, like if it's above or below one.

And when you, you line that out that are not, when are not crosses one, it's a hop bifurcation that looks just like the speed wobble, bifurcation, I mean the graph. It's amazing how like, cool those things, you know, mathematically you're like, Oh yeah, that's exactly the same as this. It's just here, it's in a, you know, you get the exact same graph if you're looking at, um, Uh, wing flutter in an aircraft, uh, in the wing tunnel.

Mm-hmm. , similar bifurcation problem, but yeah. So you, you, you have essentially two states and the system can get tripped from one end into the other. And in the one the bike is stable and wants to go straight, and in the other it wants to oscillate because each oscillation mm-hmm. is setting up the, the counter oscillation.

Um, and so like, it, it's, you know, in resonance it's more of like a runaway you, you think of like the, how that's tradition. Yeah. It amplifi forcing. Yeah. It, it just keeps growing and growing and growing. Um, and in this one it just, it, it, it's not growing and growing, but it just trips you into this spot where like it's really bad.

Um mm-hmm. and it will just shake the crap outta you at the front end. And um, and in fact motorcycles quite

[00:37:07] Randall: scary. The high performance motorcycles will sometimes have a steering damper for this very reason. Um, because you'll, yeah, you'll get these speed wobbles. And so the damper is essentially making it so there's some exponentially increasing resistance.

Um, I, I know you know this, I'm explaining it for our, our audience just in, you know, cause again, I wanna keep bringing it back down to earth, but, you know, having just like your, your suspension, you don't just have a a just a spring, you have some sort of damping circuit so it doesn't feel like a pogo stick.

Um, which is a related effect. Um, but, uh, very cool. And are not for our listeners as well.

[00:37:47] Josh: Funny. I hadn't thought about that. I haven't thought about that in like two years as we were talking like, Oh, I remember now. That was, uh, yeah. Yeah, that was, uh, But what or not was the, um, Oh shit. It was the. The contagion ratio or whatever, like how, how many people, each person would transmit to mm-hmm.

And so if it's, which makes sense, right? If every person's gonna transmit it to 1.1, it grows. If you're gonna transmit it to 0.8, it, it dies. Um,

[00:38:12] Randall: so the analogy here is that, that the increasing amplitude of that, you know, those pressure differentials, sending it to the, the system to one state or the other and causing that increasing oscillation, Is that a exactly correct characterization?

[00:38:26] Josh: Yeah. Yeah, exactly. Like you, you can take it right up to a line, um, and you don't have a problem. And then as soon as you cross the line, you're in a different state. Mm-hmm. . And, and that's where I think, you know, speed wobble for those of you who've experienced it or chase tried chasing it on a bicycle, um, you can solve it sometimes with like, the stupidest stuff.

Um, you know, one of the, the common ones is to just put a little bit of like, um, like, like a heavier bar tape or a little bit of lead weight in like your, um, Uh, your plugs. Mm-hmm. . Mm-hmm. . You can oftentimes change it with a tire pressure or a different tire cuz you can add just enough damping at the contact patch.

Um, that it just pushes it up high. You know, if, if, cause typically what people will find is like, Oh, it's, I'm totally fine. Then I hit, you know, 38.5 miles an hour and all hell breaks loose. Well. Mm-hmm. , you change the mass at the top of the system a little bit and maybe you've now pushed that point out to 45 miles an.

but if you never go 45 miles an hour, you've affected, that's not a problem. Right? Yeah, yeah. Like, oh yeah, I

[00:39:28] Randall: fixed it. I think another example that people may have experienced too is like, uh, sometimes you'll have an issue with your car that, you know, won't notice except that certain speeds and it's because of those speeds.

There is some, you know, oscillation that's happening. If it's a tire and balance or something in your drive train or the like. Um, you know, I've, I once had a vehicle that was really good up to 60 and then like 60, 61, it was problematic and then it would smooth out a bit after that and it was just like this wobbling effect that would balance out beyond that, that speed.

Um, alright, so then bringing things back down to earth. Um, this is delightful by the way. I, I could do this all day, . Um, and I, I hadn't quite appreciated. Um, the, the basic r and d and like basic science and tool building that you were involved in. Uh, so. That's, its its own topic. That's probably not one for, for a podcast of this particular

[00:40:22] Josh: def.

Yeah. I, I will say on that, I think that's the part that I think never, you know, the marketing never really tells that side of the story cuz it's just too complicated. Yeah. But if you're, if you're out there and you're, you're into this stuff, like that's the fun stuff. Like, I love launching product and, and the product itself.

But like, that crazy journey to get there is usually like, that's where all the fun is happening. And, and, and typically cuz we're, you know, you're doing it wrong, like 90% of the time you're like, you know, it's just can be months or years of like, we suck, you know, this doesn't work, we're getting our sasses kicked.

And then you, you know, if you persevere long enough, you will come out the other end and it's like, wow, we, we needed all that stuff. Like, we needed to get our heads handed to us over and over again, or we never would've figured this stuff out. Um, Yeah. I really, really enjoy that part of, um, of, of technology development or whatever you wanna call it.

[00:41:16] Randall: Yeah. Basic, like real basic r and d right down to building the tools that you need to do the r and d you want to do, um, Right. . Yeah. Very cool. And obviously like the compute power and the, the algorithms available and, you know, the switch to GPUs and all these other things that have, um, changed since you were developing that make it such that today's models are both vastly more powerful and still yet trivial in complexity relative to the system itself.

[00:41:44] Josh: Yeah, totally.

[00:41:46] Randall: Yeah. Um, well let's dive into some more practical topics. So let's talk about like, alright, so a lot of our listeners we're the Gravel Ride podcast, right? So thinking about that particular experience, um, what should, what are, what is worth, um, a gravel rider thinking about. Uh, with relation to arrow.

Uh, so things that can be done that will improve aerodynamics, but then not take away from the ride experience that a lot of riders are after, particularly when they're going to grab, you know, they wanna be comfortable, they wanna have a good time, they wanna have good control over a variety of different terrain and so on.

So what are the arrow? Um, and, and they don't wanna look silly, so they might not be, want wanting to wear a skin suit or something like that. Not that it looks silly, but, but you know, a more, a more serious enthusiast type of rider. Uh, what are the Yeah, what are the things to think about?

[00:42:36] Josh: Oh, gosh. That's, that's a good question.

Um, I mean, I think it really depends on, on what. Th the particular rider, you know, is after, I mean, are you, are you racing? Do you wanna go fast? Do you wanna not get dropped? Mm-hmm. , um, you know, do you need to carry stuff? I mean, I would say one of, one of the big ones that I, I just see and, and you know, we, we make a ton of stuff in our company and one of, one of them being bags.

And, you know, we're constantly accused of not making bags that are big enough. And so I've been on this mission for a couple years of like, you know, what is in there, , Like Really? Mm-hmm. what's in there. Yeah. And it is amazing to me just how much crap people are carrying. You know, you, you open some of these monster seat bags, it's like, man, just because you bought it doesn't mean you need to fill it or use it.

Um, you know, it, and, and absolutely there's, there's like time and place for it. But, um, you know, I. Some of the stuff like that, like, Oh, okay. You've, you know, do you, you show up on the local gravel right here and you know, people look like they're, they're almost like bike packing, like mm-hmm. , you just don't need, you know, it, it's a 40 mile loop, you know, that starts and ends at a bike shop.

Like, you, you don't need to bring a bike

[00:43:49] Randall: shop with you. Well, you, you need your coffee grinder, you need your, your mini stove and you need your neuro press. Yeah, Yeah. Um, different experience. You know, let's assume that we're going after like a performance rider who's, um, like doing, doing, you know, a hundred, uh, a hundred mile events than they're, they're training for it and they wanna squeeze out more performance, um, out of their existing setup.

Or they're considering, you know, what bike to get, what wheels to get, what, um, how to set it up, even considering bike fit. Yeah. Or, you know, clip on arrow bars and the, like, what are the different things that people can do and what are the compromises and so on.

[00:44:24] Josh: Yeah. I mean, the, I, I think certainly for gravel.

The one clear cut, no compromise. Better all around product that I can just always recommend is like a, an arrow top drop bar. I mean, it is amazing how much faster those things are than round section bars. I mean, any really, you know, like pro vibe or the zip fuca or whatever, you know, there's, I think every company makes one.

It's that big, you know. Oh, it's hu I mean it like wind tunnel speeds. It's a flattop bar can be like 28 to 30 watts. I mean, it's nuts. Yeah. Cause you're, you're replacing round covered in tape with something that's like pretty thin and shaped Well, sure. Or it can be massive, but, but the,

[00:45:05] Randall: I didn't, cuz the cross sectional areas is not that big compared to, you know, the rider and the, the rest of the bike and so on.


[00:45:12] Josh: No, it's, it's, well and in gravel it has the double effect of being, you know, shaped or ized in the direction that is also gonna add compliance, right? Yeah, yeah. And, and comfort. And so you, you know, it's one of the few products I can really look at and go, okay, that thing is more arrow and more comfortable and has more service area for your right.

I mean, better all around. Um, that's a pretty easy one to, to go with. And, and similarly, you know, if you've, you've got the money. I mean some of these, the, the integrated cockpit solutions that are out there are even faster, right? Cause it's just even less. Stuff in the wind. Um, so let's talk you, let's

[00:45:48] Randall: talk about that.

That's big, a big serviceability compromise and, and you know, fit can be a concern with that too cause it's harder to swap components and so on. How much of that is coming from, um, simply not having the cables running into the down tube? Like, can you get the vast majority of those benefits with cables coming out from, say, underneath the bar?

If they're tucked in on the bar or even coming out from the bar and dropping underneath the stem into the, the headset from there?

[00:46:14] Josh: Yeah. Yeah. My, my rule of thumb for cables that I always use cuz it's so memorable is, um, You know, Greg Lamond versus Fon in the 89 tour time. Mm-hmm. , So 2020 kilometer time trial.

Um, the eight second gap, there was more or less equivalent to Fons ponytail, Right. As we, we loved to joke about a cyclist, but was also the equivalent of one number two pencil length worth of cable housing. So, and

[00:46:46] Randall: this is, and this is true even if the cable housing is say, in front of the head tube, so it's going to be disturbed by the head tube anyways, cuz you're getting the drag off of it.

Be, you see what I mean? Like, so I, I'm trying to hone my understanding of the

[00:46:59] Josh: Yeah. I mean, you think, Yeah. So I, I would think, uh, good way to put that would be that, Yeah. Putting, putting a slow. Crappy thing in front of a smooth thing, you're, you're still getting the drag of the slow, crappy thing. Yep. Um, and you may actually be worsening the flow, um, on the arrow thing.

So Yeah. Got it. Absolutely. Still, you still have that effect. Um, you know it, and it's hard to say, you know, in some cases, you know, it's, it's close enough or it's just in like the goldilock zone where it's a good distance away where you're like, Ooh, we can kind of make them disappear. And they become, you know, uh, a almost like the cable isn't there, but that's not typically what we see.

And typically, you know, you, you throw a bike in the wind tunnel with that and then you rip the cables out and you run it again and you're, every time it's like, Oh shit. Big difference. Difference. You've, in

[00:47:50] Randall: terms of watts, like a few watts here, like, so, so the handlebar is the big one, you said as much as 30 watts at wind tunnel speeds, which granted gravel riders generally are, are, we're

[00:48:00] Josh: not going that miles an hour.

But you, Yeah, you we're out for a long time. Yeah, but you are out there for a long time, so you don't have the speed. But yeah, you, you definitely have the, the, the potential time saving. So, yeah, I, you know, hidden cables. I agree with you. Total pain in the ass. And, you know, my God, I've spent a career working on world tour bikes and, and you know, Ironman, world champion bikes and things like that.

And I, I feel everybody's pain, you know, people are always like, Why is the industry doing this to us? Like, like, Well, cuz you want it and cuz it works. I mean there's no, like, it, it's a pain in the ass, but it works. Mm-hmm. . So anywhere you can get rid of cable. get rid of cables, um, you know, skin suit. I have to say not everybody loves it, but man, it can be a huge, huge difference.

Uh, I mean, you look at, you know, we were just out at lead, uh, Leadville and Steamboat, and you know, all the top. Guys at Leadville and skin suits now, cuz it, it makes that big of a difference. Um, arrow bars can be huge and, you know, I think that's, that's one I I think everybody's got their own sort of flavor that they like.

But, you know, to me, like for gravel, a stubby, a stubby bar that has functional pads mm-hmm. , um, really can be worth it just because it's a different hand position and it, it's enough that it, it's effectively changing your, kind of, your whole torso position and it, it, it's just giving you a, a break all around.

Right. It's different pressure points in your shammy for the time that you're using it. It's different, you know, muscles in your back. Um, I think there's a good, this is the, the extent of my physi physiological knowledge, but I, I think it's good to, to mix things up. Um, like that. I, I know a lot of people have kind of gone to these super.

Narrow, stubby, I don't even know what you call 'em. Like semia bars that Yeah,

[00:49:46] Randall: mini arrow bars.

[00:49:48] Josh: Nowhere to put your, nowhere to rest your weight. And, and it just feels like everybody I know using those is constantly complaining about their wrists, you know? Um, and so I, I, again, not a physical, but the change

[00:50:00] Randall: in the change in frontal area, um, is that just an unmitigated benefit or are there circumstances where you can reduce frontal area and, you know, have a negative result within the realm of, you know, changing a Roger's position?

[00:50:16] Josh: Yeah, you know, a lot of it depends on your, your baseline and, and how good you are. Positionally, I think, you know, when, you know, we do a lot of position training with top athletes and you know, the. The best place you can be that's not an arrow bar is on the hoods with level forearms. Mm-hmm. , right? Like that's the, and and ideally with relatively narrow bars,

[00:50:37] Randall: so, and perpendicular upper arms as well, presumably,

[00:50:40] Josh: or give or take.

Yeah. Yeah. Yeah. I mean it is, it's, you're gonna roughly get there depending on what the rest of the position looks like and, you know, obviously different body shapes and whatnot. But yeah, I mean, you think horizontal forearms are keeping that pretty much out of the wind. Mm-hmm. , Um, and, and they are also keeping it, it's just hard to hold that position, um, with, in a way that you're also still opening your chest.

Because, you know, you were really trying to keep air from getting blocked up under the chest. And when you get a rider doing that, they just always kind of form, which I say always, I'm sure there's some counterexamples out there, but they, they almost always, um, kind of adjust their back and their shoulders in a way that they kind of turtle their head a little bit.

You know, the head comes down and you're just kind of now pushing more air up over the body and less down into it. Um, but from there, arrow bars are almost always an improvement, right? Cuz you're narrowing the arms, um, you know, you're tightening things up even further and now you're pushing more flow around the sides, um, and less into the chest and less into the hips.

And there's some physiological things. You know, people, you know, wide hips, big hands, certain shoulders, certain back shapes, right? That's why we go to the tunnel, you know, it's, it. 90% of the time, you could look at somebody and go, Oh, do this, this, and that, but man, 10% of the time it looks good and you run it and you're like, That's not good,

We can just find a different solution. Um,

[00:52:10] Randall: yeah. So air bars are huge. Another thing that we're starting to see is, uh, so BMC has their new cas uh, uh, line. They went with a super narrow, uh, handlebar, so narrow at the hoods, and then, you know, flare at the bottom. Uh, that seems like another thing that again, is, Well, I mean, on the one hand, yeah, you're getting narrower, but on the other hand, you're also closing up the chest and maybe, you know, you're not getting as much oxygen, like air turnover or something.

Or like, are there issues where I, so

[00:52:38] Josh: I, I have been beating the narrow handlebar drum for 25 years. Um, you know, I am yet to actually see or be told by a real physiologist that that whole. Oxygen lung thing that we were all told as juniors is true, is an issue. Um, yeah, I I've just, yeah, we've just never, I mean that, that I know of and I'm sure somebody out there will say, Oh, here's a paper.

But, you know, I, I know whenever we've studied it, looked at it, we've looked at it with athletes, I mean, look at what's happening at the world tour. A lot of that is, you know, we've been beating that drum. I'm starting to see that for years, and people are doing it and they're winning. Um, so, you know, and I wonder

[00:53:17] Randall: why aren't we seeing it with extreme flare as well, like a compound flare at least, so that you can still keep a, you know, a reasonably vertical lever position because then you could go even narrower and have, um, still have the leverage for the descending and so on.

Is that a

[00:53:32] Josh: tradition thing? Yeah, I, yeah, I think some of it's that. I think some of it is just, you know, how far do you really wanna push the uci? Um,

[00:53:42] Randall: you know, oh, the UCI cares about the flare in your bars.

[00:53:46] Josh: Oh, they will. Yeah. I mean, I mean, I think there are actually rules putting some limits on that, but yeah, at some point it's gonna look funny enough that you're gonna draw attention and they're gonna go, Wait a minute.

Um, and, and you know, we've, we've

[00:53:58] Randall: seen them, I've got a 28 centimeter wide bar with huge flares on there, and I've got specially made levers that come off of it so that I can actually still touch them from the job.

[00:54:07] Josh: We have seen it with, I, I can't remember the name of that bar, but I think it's out of Belgium or something.

But it's got like, you know, uh, 180 millimeters of reach, um, super narrow with long, and you can kind of lay your forearms. Yeah, yeah, yeah. I remember seeing that and they quickly were like, Nope, that's out. Um, so I, you know, I think we just, people are, people are cautious. I think the, the setups that are working now, um, are very largely built around that, uh, three T track bar.

I can't remember what it's called, but, uh, I know. You know, it's got that kind of cool like wing, like gulling shape to it, but it's super narrow, arrow tops, um, relatively vertical, uh, drops. But, but that's a bar that the ucis allowed for years, right? And so I think that as a, you know, when, when conversations are happening behind closed doors, that's the kind of thing of like, Oh, well this looks enough like that, that if they call us out, we, we go in there and be like, Well, it looks a whole lot like this thing that you've allowed for 20 years.

Um, you know, we, we have tons of those conversations. Yeah. So, so I, you know, I, I think, but I, I will say, I, I think too, that's where, um, you know, a lot of people might look at the pro tour and things that they're writing. Oh, well if this worked, they'd use it. You know? I mean, that was what people told us when we were building zip in the early days.

Well, if they worked, the Pro Pros would ride it. I'm like, Yeah, but they. They don't know what they're, they don't believe in aerodynamics. You know, they, the pros, they don't riding

[00:55:34] Randall: super skinny tires at super high pressures cuz they felt faster for a long time, even though, you know, at least, well, you know this better than than I do.

I mean, the data has been saying for quite some time that it's more efficient. Never mind the accumulated fatigue that you get when your body's just being, you know, rattled at, you know, high frequency over the course of many hours.

[00:55:56] Josh: Yeah, yeah. No, it's, you know, that I would say they're quite often the last, at least as a group to change.

Right. But you, you are seeing it now. I mean the, you know, and, and, and you know, the team like Nios hiring a guy, hiring Dan Bigham to come in and, you know, you, you are seeing some changes, right? Uh, that when teams are bringing full-time people like that in, um, we are gonna start moving the needle there, but it's still a delicate dance with the.

With the UCI and, and all the sport governing bodies, right? Nobody, You hear it all the time. Nobody wants a repeat of the whole fna. Uh, I don't follow swimming, but I was the technical, uh, committee director for cycling at the World Federation of Sporting Good Industries. And, uh, at the time when FNA Band banned all of the super tight, uh, swimming suits, and it was just a cluster, right?

I mean, they just came out and said, Nope, you've pushed it too far. We're done. And if the whole industry was sideways with like, we've invested millions of dollars in this and the records are breaking, and people wanted and on and on and on, and they just said, Nope, you're done. And, uh, I think it took them five years to under undo all that damage.

You know, I mean, you just wanna

[00:57:11] Randall: something parallel with running too with, uh, carbon fiber insoles and like what is, what is allowed in terms of the amount of spring that can be delivered and so on. Um, Yeah, I, I see, I see them showing up on my local run. And, um, I might have to get a set just to keep up with the people I used to beat, to keep up with

[00:57:29] Josh: It's totally true.

[00:57:31] Randall: Uh, that's, I mean, that's, that's, to some degree, that's the nature of the game. And that's why in, in significant part, that's why the gear is as good as it is right now is because, you know, people are looking for, as you would say, those marginal gains. Um, yeah. Um, I wanna dive in. So, uh, I want to put, bring in a few, uh, listener questions.

Uh, so we posted in the ridership that you were gonna be coming on, and so we had some folks asking questions there. Probably the biggest one that came up was, um, talking about, you know, we've, uh, Craig and I brought up the rule of 1 0 5 or 5% on the podcast before, but, you know, citing, citing it, it's not a deep understanding, uh, at all.

So tell us about how that emerged in. How it applies. Um, you know, particularly in the gravel scene where you're looking at tires that are much bigger. Um, and I mentioned, uh, earlier that, you know, specialized as a video for their reval wheels where they're running a a 42 mill tire on i, I think a 35 or less external rim, and they're claiming some arrow benefit.

Does that seem plausible? Is there, uh, given, given, given what you have seen in the wind tunnel and in your modeling?

[00:58:41] Josh: Yeah. Um, yeah, it's totally plausible and I guess, we'll, we'll start with rule of one. Oh, so rule 1 0 5 was really, you know, I, I realized pretty early in my career that you had to come up with sort of rules of thumb for things or nobody would listen to you

Mm-hmm. and, you know, spent two years traveling Europe trying to sell Arrow. Sell World Tour or pro tour at the time, uh, directors and team owners on aerodynamics and you know, I mean literally got thrown out of every single team, team over there. Uh, I mean, it was just, we just got laughed out of the room.

Just imagine

[00:59:20] Randall: any of those team directors could have just adopted it at that time and had this huge advantage and didn't,

[00:59:26] Josh: uh, that was, I mean, I always said, you know, Uli at srm, thank God, you know, he was developing his thing. And when I walked in to pitch Reese, um, he was already on power meters. And so that, that's when it hit me, like really the moment of like, Oh shit, the wa is the, is the currency here.

The wat is the, the lingo Franco, right? Because we talked grams of drag and this and that and, you know, and, and a lot of them were still talking about calories and kilo jewels and, um, bpm, you know, these things. And it was like heart. Exactly. And, and so, and so it was like, Oh, wow. I have Watson, you have Watts.

Okay. We're, you know, Rosetta Stone baby. Like we're, we're on, We, let's now, now it's

[01:00:08] Randall: an optimization function.

[01:00:10] Josh: Right, Right. And, and now it's, it's what's used. But I mean, that was truly the moment of, uh, you know, I left that meeting and we called SM and bought a bunch of, um, a bunch of power meters and then kind of, that became the dog and pony show, right?

Of like, No, no, you can see it in the power. And we can, I mean, it was, you know, this was 2000, 2001. So, I mean, this was like, like very early days, right? I mean, this was like, yeah. Like, you know, like pre power tap, like, oh yeah. Hundred and 60 bpm. Like, well that's, um, which is, or my favorite at the at the time.

Would, you'd get, And the triathletes were great at this, like, like, I, I raced on your wheels and I, nothing changed. And you said like, Oh, well what, what was your race pacing strategy? Oh, 22.5. Like, Yeah. Okay. Well here's the thing. So 22.5 is always 22 5. I bet you ran like a monster. Oh shit. I was like five minutes faster in the run.

Like yeah, cuz you had all the, all that energy left. But, but you know, it's kinda like, note to self, if you ride at 22 and a half miles an hour, it doesn't matter. Nothing else matters. You will only ever go 22.5 miles an hour. Um, yeah, we just, it, it was just a different time. Right. And, and, uh, so I had been, I think 2001 was the, for 2000.

Yeah. 2000 was the first time I was invited to the tunnel with, uh, Lance Armstrong and, and Yohanne and that whole group. And um, you know, obviously they were on zip discs, which truck was buying. Um, but head was their wheel sponsor other officially. And so, um, they had that head three spoke wheel and, and I noticed in the tunnel the bike always had this like continental TT 19 millimeter continental t.

Tire on it. And you know, we had tested that wheel in the tunnel and it just was always just fine. But, you know, the one we had that we tested was our baseline tire at the time was of course, of CX 21, right? I mean like the, probably the most race tire in the history of ever. Um, you know, that thing had like a 30 year dominance at the top of the of the pro Peloton.

And uh, like, wow, that wheel looks amazing with that tire, but it's pretty averaged whenever we tested. And so really fell down this rabbit hole of like, what are the tires doing? And um, Similar time, uh, Craig Willett, who had the bike tech review, one of the first like online blogs of the late nineties, um, about bike technology.

He had, he had gone and done a wind tunnel test of disc wheels and he borrowed a zip disc that had a 23 millimeter tire on it that was pretty, pretty well used and the wheel just looked terrible. And so, you know, we were trying to figure that out and combat, you know, oh, the, the disc cover is way faster than a real disc.

And like yeah, but that had a 19 millimeter tire and so got Andy to let me go to the tunnel and just look at rim tire interaction. And we just spent like a whole week doing just that. And what we came out of there with was this realization that, and it makes sense, um, when you just diagram it out. I've got a YouTube video on this that people can look up rule 1 0 5, but, um, If you're gonna keep flow attachment on the leeward side, right?

So the, you got the Winward side, like the side the wind is coming from, and then the leeward is, you know, the opposite. So this is assuming

[01:03:35] Randall: you're gonna keep, it's coming at an angle. There's some yaw involved at an angle, right? Yeah.

[01:03:38] Josh: Right. Yeah. And it's almost always coming at some bit of angle, right? Yeah.

It's almost never purely straight on. So, so we had to really start thinking in terms of, um, Oh, okay. There's always some crosswind I think that hadn't fully been appreciated. Um, but then, you know, if you wanted leeward side attachment, you the rim couldn't be in the shadow of the tire because the air separates pretty early off the tire.

Yeah. Okay. And so you can just visually look at it and see, oh wow. It, you know, if, if they're equal at two degrees of y the rim is shadowed, right? And so everywhere beyond that, there's, your attachment is hopeless. But if the rim is wider, Especially if the rim is wider up at the tire, we, we could maybe keep that flow attachment quite high.

And so as a result, you know, the, the rims of that era, the sort of V-shaped, U-shaped rims, um, people were doing in the nineties, early two thousands, um, became toroidal and the hybrid toal and, and some of these other variants that we ended up developing. But they started getting wider. And, uh, you went from, you know, the, the flow attachment would break off at between two and a half and five degrees and all of a sudden, I mean, we could keep flow attached at 12 and a half maybe.

You know, I think when we did the 8 0 8 in, uh, 2003, 2004, um, that had flow attachment at like 17 and a half degrees. I mean, that was just a, not never,

[01:05:04] Randall: it's in a, in, in a wind tunnel, right? So the bike isn't moving relative in a to the flow, so you're controlling that angle. Um, Right. Yeah. So 17 and a half degrees, um,

[01:05:13] Josh: which is, yeah, which was nuts, right?

I mean, it was at

[01:05:15] Randall: 30 miles an hour. I mean, that's almost a side wind tunnel. I go, Right. It's almost

[01:05:20] Josh: ridiculous. Yeah, yeah. You, you do the math there and you realize it doesn't happen very often, but Yeah. But what that means is, is you know, the percentage of time that you're writing in conditions where the flow is attached is extremely high.

You know, you think of those early V-shaped rims, you maybe have flow attachment down in the five to 10% of writing time. Mm-hmm. , and by the time we get to 8 0 8 and Tory, and, and some of the shapes we have now, you probably have flow attachment in the 90%, 85 plus percent, uh, of ride time. I mean, it's just a, a much improved experience.

And then where

[01:05:55] Randall: presumably there are, there are different parts of the rim where, uh, that attachment is more, more relevant. Like the top of the rim is traveling at twice the speed of the bike. So it's going forward and you know, the bottom is stationary. And so like, can you tell, talk about like where, where most of the benefits are coming from in terms of where on the wheel and then in terms of like the depth versus the width and, and things like that?

[01:06:18] Josh: Yeah, so for, for pure drag, you're sort of like, uh, three o'clock, nine o'clock positions are really key because that's where your section is shortest relative to flow. Um, and that's also where from a handling perspective, your, uh, your lever arm, so to speak, that the wind has against you is the longest.

Right. So that's where, you know, if the, you know, you think of the wind trying to like torque the bars out of your hand. Well, you know, that's where he's got the largest torque wrench. Um, you know, you get higher in the wheel, it's shorter. Um, but then as you get higher in the wheel, now you're, you know, you should be

[01:06:54] Randall: force.

Well, and you should be able to keep, Am I right that you should be able to keep flow at attach if you have a deep section wheel keep flow attached over a very long distance because you have essentially a continuous four F surface. Yeah. Or as deep as that deep section rim allows. So the deeper the rim.

[01:07:10] Josh: Yeah, exactly. Yeah, yeah, yeah. As you slice a wheel and you keep coming up, you see, you know, you go from like, you know, it's across section, cross sectional shape at three, and now that cross sections getting deeper and deeper and deeper and more elongated. Um, and, and that's why you, you typically, um, even, even bad rim shapes tend to not be that bad as you get higher.

Right? Because the tires become a, a essentially a sharper, uh, leading edge. And, you know, things tend to, you know, your, your section over which the flow is, is, you know, in some cases three, four times as long. Yeah. Um, and so that's where, you know, you, But as you improve that sort of three and six area, you also.

You do end up improving things up there as well. And then of course you get into problems of, you know, like that first 8 0 8 was 27 millimeters wide and designed to be run with 21 millimeter tires. But in an era where the bike makers were obsessed with, Narrow. And so now you all of a sudden have a problem of like, you're damning up airflow between the rim and the fork blade because the, for, you know, well, that's insisted on having their fork blade super squished together and, you know,

[01:08:18] Randall: tight tolerances and now no one can run a bigger tire on those old bikes.

I actually wanted to ask you about the, um, the Lotus, um, bike, the, uh, the Hope HB dot Lotus Track bike. Yep. Um, so this is a, a really radical bike. I'll try to remember to put a link to it in the, um, in the show notes, but it, you know, it seems like the core, the core thing that they've gone after here is pushing those four blades as far away from the wheel as possible and doing the same thing with the chain, uh, the seat stays.

Um, yeah. So talk about that. Like, why, why don't you see that on road bikes? Why don't you see like a, a super wide fork with a skinny tire

[01:08:55] Josh: in the middle? Yeah, So, so it's funny, you know, we, we, we actually. Originally did the late nineties at zip, we, we made a fork that had a hundred millimeter wide crown and vertical legs.

Um, and it was actually welded by a local guy here out of, um, ar strut from an indie car. And, uh, we put that thing in the tunnel and realized like, Holy crap, this is really fast. And, and that's where we also, it, it's kind of a true story around why zip abandoned the three spoke, three spoke wheel only in the tunnel can be pretty quick.

Three, spoke in a fork, was nowhere ever nearly as fast. Um, and oh, because the

[01:09:30] Randall: interaction with the

[01:09:31] Josh: for blades, Right. And, and that's, you know what I always tell people, the easiest way to think of this is the sound. Oh, right. Yeah. Nobody,

[01:09:39] Randall: You're getting these pressure buildups and releases each time the, the, that big spoke goes past the four.

Ah, okay. And then the further way you.

[01:09:49] Josh: Yeah, it gets quiet. And so that's, we actually built it to try to understand that and that's when we, we put it on the zip 3001 and I mean, remember running that? We were just like, Holy shit, that's the fastest bike we've ever tested. That, that, It's funny the guys at zip still take that bike, um, back and, and use it as a benchmark to test.

And it's, I mean, it, it's to this day as fast as almost anything out there, um, even though. 25 years old now or whatever. Um, and do you have

[01:10:14] Randall: to be a certain distance way or is it, is it, does it get exponentially better? It gets further away, or, Well, actually no, it gets the biggest benefit should

[01:10:22] Josh: be, is immediate.

Yeah, no, you, you definitely lose you. It's definitely diminishing returns and that's why, you know, at a hundred millimeters you're fine. Now at a hundred millimeter, you know, that boxy shape, there's some real handling, um, issues to solve. Right. I mean, the fourth wants to kinda like parallelogram, um, Sure.

Yeah. Side loaded. And so, you know, the forks are gonna end up being heavier and there's more service area and all that stuff. Now, what the, the British team guys and Hope did was they took it one step further and said, Well, if we're already gonna come out here and try to build that gap in, let's push it out even further to try to put it in line with the writer's legs.

Mm-hmm. in, in the hope that, um, you talked earlier about, you know, it, it, it's not always very doing much for you to put a crappy thing in front of a fast thing, but it can help you to put a fast thing in front of a crappy thing. Right. And so mm-hmm. , by putting a, a, a very beautiful air foil out directly in front of the rider's legs, they're able to control the, the air downstream condition hitting the leg.

And so now you have the ability to, like, do you wanna turn it most likely outboard? Um, or do you wanna just disrupt it in a way that you're reducing the pressure on the front of the leg? Um, you know, I, I would think of that almost like, you know, you look at, uh, Diving competitions. Right. They always have that like little spray of water that's like breaking the surface tension on the water so that divers don't die when they hit it.

You know? And you can kind of do that aerodynamically, Right. With upstream and downstream effects, you know, you can kind of, um, put a different type of flow onto something that you know is less arrow. Right. So we might like put a little flow energy in there. Um,

[01:12:01] Randall: so you're basically curling, cleaning it up.

You're, you're essentially cleaning up the airflow or like conditioning the airflow before it

[01:12:07] Josh: hits the legs. Yeah. You, you may actually be dirtying it a little bit. Yeah. Before it, it hits the legs. . Hmm. Super interesting. So I, I, I, I wasn't involved in that project, so I can't speak for exactly what they were up to, but yeah, I would, I would be interested to see.

And then, and then they did the same thing in the, the, um, seat stays. And, and there you would wanna, um, you know, you would actually wanna be recapturing and then now cleaning that flow, right? To leave it as smooth as possible. So, you know, you may in the sense be creating sort of a, this, um, interesting like little interstitial area between two air foils where it, you have.

Slightly more optimized condition for this, this mess that is this spinning leg, Right? Especially in track where the legs are huge. Mm-hmm. . Um, and so it's, it's an unique problem to solve. Cause it's really, it's not obvious, right? The, the obvious answer may be completely the opposite of what you actually wanna

[01:13:02] Randall: do.

Well, and let's bring this down to a more practical application of this concept. I mean, I, I don't, I don't think we're gonna see bikes, um, for mainstream audiences that are pushing the fork blades and the seat stays, you know, that far out. That probably doesn't make sense. But pushing them further out relative to the wheel, I'm surprised we don't see that.

Like the, the structural issues. Um, I mean with, with advanced Composites, you can solve that with relatively low weight. Three T has their, you know, has a, a fork that fits a 2.4 inch gravel tire. Yeah. And so that's, I mean, and it has a really, you know, uh, it has a small crown. It's not this big beefy thing and it's quite lightweight, so presumably structurally you could do it.

So I wonder why you don't see it with road bikes.

[01:13:47] Josh: I, I mean, I think you've, you've certainly seen the move in that direction over the last, I I'd call it 10 plus years. Right? I mean, Track Trek was really the first one to go there cuz they knew they had an issue with that three spoke wheel that lands was riding.

I mean, you look at the, you know, the truck TT bikes of the two thousands had way wider fort crowns and, and rear stays than anyone else had. Right? Cause they, they knew what wheel they were working with. Um, you know, you've seen some of this, uh, In road. I would say Trek is still one of the, the big ones, but, um, or probably one of the, the class leaders on this, but also you've just seen other things happening, right?

The tires then got bigger, which made the rims need to get bigger. Um, and then of course everything had to get taller for clearances. And so, you know, now I think they're, were, we're, we're much more threading the needle for like, how can we turn this race bike into a customer bike and vice versa without having to make, you know, a million custom molds and custom sizes.

And cuz cuz the, you know, the, the kind of cool trickle down reality of, of our sport and what we're doing is that, you know, the, the bike that you buy off the shelf really does come from the same mold that the pro bikes come from cuz that's so expensive to make those molds that, you know, nobody's getting custom.

Yeah. Um, You know, it, it, I mean, there a lot of really good stuff has happened, but you do put yourself in some interesting, um, pickles, so to speak, right? Where, oh, well technically this may be the right answer, but will the customer, you know, accept it? Will they understand it? Do we have the money to market it?

You know, a lot of the, a lot of these, especially more out there technologies that are counterintuitive, um, they can take a fortune to market to get people to change their minds. And if, and if you don't have that money, um, you know, then that product becomes a flop. And then that feature that made it flop becomes the thing that doesn't work and keeps you from selling bikes and, you know, and it'll take 20 years to repair that cycle.

So, mm-hmm. , Um, you know, I think there, there's a lot of complexity, uh, behind these things that not everybody. Thinks about or because they don't have to . Yeah. So,

[01:15:58] Randall: yeah. Well, and I spent some time at, um, at one of the big companies, and so got to see just how deep that complexity can be and, and how, uh, and how it truly is the case that we are in a sport where you can ride something that, um, is very much trickled down.

And it's not entirely BS though though, frankly, also you see lots of, uh, things that are added for the purposes of marketing that kind of come and go, you know, magic elastamers that get bolted to a frame and, you know, they tell some sort of resonance, stamping story. Uh, won't name names, desserts, but, um, Yeah, yeah.

[01:16:33] Josh: Yeah, we've, we've had our share of those and, and I think, you know, too, I mean it really, the, the industry continues. I, I enjoy, I mean, it, it continues to be a nice mix. You've got some companies that are like almost just pure marketing companies, right? And you've got some other companies that are almost pure technology development companies and, and a little bit of everything in between and, and, you know, the, the pendulum swings, right?

I mean, it, it is nice to see that the, you know, we certainly lived it with, um, with csc, you know, that, that you had, you know, specialized and Cannondale and Trek were dominating and then our scrappy little, you know, group of misfit toys like showed up with CSC and all this arrow stuff, and all of a sudden we're like punching way above, above our weight, right?

I mean, that was a true, uh, Moneyball situation when you look at it historically, right? I mean this, this team that had an entire team budget of less than Lance Armstrong's salary, um, became the UCI world number one team. And, and we did it not just through the marginal gains, but those marginal improvements of, you know, if you can get every writer to finish on average, Four places higher than they would've, right?

I mean, you're just like, you're just working every last little angle. Um, but all of those aggregate into something, you know, I remember a couple years in we're like, Wow, we're gonna be the top three team this year. Like, that's crazy. You know? Who's your bike sponsor at the time? Velo. Yeah.

[01:17:59] Randall: Okay. I was gonna, I was just gonna say like, that was, um, I'm thinking like Gerard and, and Phil White, uh, Jar Ruman and Phil White.

Um, and yeah, I mean, they just had so I didn't realize that that, that you guys all collaborated. I hadn't found that connection a little bit

[01:18:15] Josh: before my time. Once we, once we got BNA interested in the wheels, he, you know, the, the, uh, Shao Campy at the time, str. A player yet, um, you had to take full grupos.

Mm-hmm. it, which meant, you know, included like wheels and shoes and all this stuff. And so we knew if we were gonna break in, we had to put, like I said, I mean truly, we, we called ourselves the island of misfit toys. Um, and so we went and got Phil and Gerard and we got cloudy at FSA and we got Ram to come in as like a, a cassette and chain sponsor.

And, you know, FSA was cranks. I'm trying to remember. I think we were buying the du shifters. But yeah, I mean, that whole thing was put together. I, I always love, I tell the story, First time I met Phil and Gerard, they were. They were, they were in this, um, hotel at Las Vegas for the Interbike Show called the Tamas Chanter, which was like one of the SLT worst places on the strip.

And, and we, we stayed at this horrible place, uh, off strip, so it was maybe even worse.

[01:19:18] Randall: But those places tend to be really cheap cuz they want to get you into pull their, their one on bandits. I've, I've, I've done that before. Just inter bike

[01:19:26] Josh: backs and it's, Yeah. But, uh, but, but so I, I hear about them through one of the, the team mechanics, like, Oh, you, you need to meet these guys.

You know, they're, they're also looking to break in and, um, Andy and I go over there and there's just this smell, you know, of like lacker, like are they people huffing paint, you know, what are they? . And it's Phil and Gerard are painting the bikes for the show in the parking lot, and they're hanging them to dry in the shower of the room.

Wow. And wow. And he was like, and of course we met him within five minutes. We're like, Okay, you guys are like us. Like let's do this. And so, yeah, over the next, that was probably God, 2099, 2000. But, uh, but yeah, so when, when we had this opportunity to break in it with cse, it was like, okay, let's, like, let's get the band together, you know?

And man, we just got all these crazy folks together and everybody, like if you wanted to come in, it had to be you. You had to have the data. You know, you didn't have to have money, but you had to have the product. And, um, you know, that the, the structural advantage that that team had for the first really four years, I mean, was, was.

Huge. You know, it was like they were just, you know, we, we would joke with them like, you know, you're, you're basically riding a time trail bike compared to what everyone else is riding. And, you know, in time they believed it and it really did be, well we said at the beginning of the show, it became the placebo that was also the real thing.

Mm-hmm. . Mm-hmm . Um, you know, and, and, and then you would have team, I mean, I, I think where it got really excited, you, you would have writers come in from other teams and see some of like the power numbers and the, you know, cuz we were there all the time chunk testing and kind of doing that whole thing. And, and then of course the word spreads, right?

And now the other writers know what those guys are doing. And so that becomes like, well shit, that's not fair. What, you know, those guys have these arrow bikes and these arrow wheels and. You know, like they started, I remember like speed play when they, you know, Richard brought the arrow pedal and, you know, there were writers and other teams were just like, Oh fuck.

You know, it was just like, like, Oh wow, we've really got them now. You know, Not, not only is it, is it a placebo for our writers, but , it's totally working against all the other teams. Um, you know, and, and that whole thing. We did that for God. It was a great time. We did, and then we did Cella test team with Cervelo and one of the founding members there.

Yeah. We, it was hell of a hell of a good time.

[01:21:47] Randall: Oh man. I've mean, and changed the sport. We really, Yeah, yeah. Totally. Definitely changed the sport. Definitely. And not just this sport. I mean, Gerard, what he's done with, um, Open and I, I think he's co-owner of Threet now. Um, the open up, I think defined the kind of the one.

What I describe as the one bike segment, it was a bike that could, you could literally have a single bike that does everything in the geometry are allowed for that. And he had the tire clearance and everything else. He had that drop chain stay. And we take all these things for granted now, but he was innovating, you know, as soon as he left Cervelo, um, continued on that path.

Um, but yeah, I, I remember, um, salivating over those bikes, and uh, now, you know, every, every company has an a bike and even their non-a bikes have a lot of arrow considerations built into them. You know, the tarmac being a prime example where they kind of merged it

[01:22:36] Josh: with bench. Yeah. I, I think that's, to me, that's the most exciting thing happening, right.

Is I think we are gonna kind of converge on, it's a bit of a right answer, you know, that, that you are gonna have the, the light bike is gonna be also a very arrow bike and you know, we're already at a point where we're playing the new and hopefully

[01:22:54] Randall: comfortable too, which is another thing that you can get some.

[01:22:59] Josh: Yeah, and I, you know, we, we worked with, uh, when, when Matt Haman won Rub, you know, that was, we had done a bunch of work with, with the team around what bike to ride there and what wheels and tires and pressures. And that was the really, the first time I'd ever seen that Scott was the foil, whatever their, their a bike was, it was equivalent in comfort to their lightweight climbing bike.

And, you know, the riders were kind of on the fence of like, Oh, that's the, a bike, the climbing bike is more comfortable. Like, no guys, it's not like . You have an very unique advantage here that your, a bike is as comfortable as the climbing bike. So you ride the arrow bike and, and you know, if, if you don't know, you don't, you don't know.

But the companies are figuring that stuff out. Man, what a, what a difference, Right? When you can be comfortable and go faster. That's pretty awesome. Well, and that's

[01:23:52] Randall: a very natural segue into, and I, we'll, we'll probably time limit this cuz we're already pushing well over an hour here. Maybe we'll have to get, have you back on at some point.

Uh, cuz this has been a lot of fun. Uh, but tire pressure, like I, you know, I'm of the opinion that, you know, the transition to wider, wider rims and wider tubus tires and lower air pressures and so on is one of the single biggest advancements, uh, in cycling, at least for the recreational slash enthusiast rider that's come around.

It's like the whole gravel segment is essentially enabled by, uh, dis breaks and tubus tires if you think about it, because you can ride that terrain, um, on, you know, what used to be. Actually, I mean, today's gravel bikes are essentially better versions of, you know, the original cross country bikes.

[01:24:38] Josh: Um, Yeah, but a hundred percent.

Yeah. Yeah, a hundred percent. Yeah. I, you know, I think that's, I'm right there with you. I think those are the two really most important advancements, um, for people riding today, you know, with Arrow probably in third. Yeah. The, the tire pressure thing, you know, I think is really the, again, it's kinda like the, the arrow top road bar.

I mean, it's one of those places where you really can't have it all, right? Mm-hmm. , Yeah. You can be faster and more comfortable and have better grip and be less likely to puncture. Yeah. If you just get your tire pressure. Right. Um, and you know, it's not always the easiest thing to solve. I mean, we. Hundreds per year, probably hundreds of optimizations for, for teams and athletes.

And, uh, you talk about the, the, so tire pressure calculator, you know, is Yeah. How's

[01:25:26] Randall: that? How does that work? How did you, is that a, a simple or a very complex

[01:25:29] Josh: equation? Um, so, so it, it, it's both. So we, a lot of what we do particularly around like Reba and some of these key events and the Olympics in the world championships and the tours, um, people will have us come in and say, Hey, you know, here's, here's my rider, here's weight distribution, here's the, the course, um, what's the optimal pressure?

And, and you know, tire pressure is a really hard one in that, you know, so much of, of what we're after in cycling are these like maximize, minimize variables, right? You know, I want max stiffness and minimum weight. And with tire pressure, it's like I want just exactly the perfect one that's optimized somewhere in the middle.

You're like, Well what is that number? Ah, we don't know. Um, And so that's where, you know, that's hard, right? Our, our brains love maximize and minimize. That's why we have, you know, that's why we still have so many weight weenies. Like, it's just

[01:26:20] Randall: fun and it's, and it's easy to market as well. You can tell something, it's easy tos lighter, and they can pick it up.

Like, pick up my bike at the coffee shop, See how light it is. Isn't that amazing? And, and, you know, sell 12, it's

[01:26:31] Josh: also, but it's also fun. I mean, you buy that stem that's 40 grams lighter and you take your old one off and you weigh them, you're like, Yeah, it's, you know, like you, you know, you, you, you got what you paid for, right?

And, and with these optimized problems, it's placebo effect, like, yeah, totally. But with these optimized ones, it's hard. Like, well, I don't know. That one doesn't feel faster or it feels different. It's, uh, you know, like how do I see it in the data? Well, we have methods. Uh, the, the CH method is the one that we use with, uh, some other various technologies, but.

You know, we can go out and, and have you ride laps and tell you what the optimal tire pressure is for you on that course, right at your weight with your tire. Um, using

[01:27:16] Randall: acceler, accelerometer and things like this to look at vertical deflection and things like this. We,

[01:27:21] Josh: so we, we actually have a whole bunch of cool things that we use, but all you really need, um, and you, you can do this at home and if you look up the CH Method by Robert Chung, it's also called Virtual elevation.

All you really need is a power meter and a GPS enabled, um, computer that you can get your data out of. And, and you know, Robert, who's a, a dear friend of mine and one of the smartest humans I've ever come across, you know, he's a demographer at Berkeley and, uh, just a brilliant guy. And, but he says it best, you know the thing.

You know, engineers were taught to like, use, ever find ways to get ever cleaner data. And demographers are always stuck with crap data. Mm-hmm. . And so they developed all these other tools to work with bad data. And he had had this idea, I think watching one of the world championship events of like, well if I could just, you know, if I could just fix something, um, if I could just fix a couple variables, I, I could cal try to calculate, um, CDA and cr uh, if I had the power files.

[01:28:28] Randall: Define the terms real quick. Uh, just, Oh,

[01:28:31] Josh: so CDA is, is like your coefficient of drag times your area. Mm-hmm. , um, so it's a, a CD is a one-dimensional coefficient. Engineers love one-dimensional coefficients cuz we hate units. Um, and so we use cd, uh, that, you know, like a. A sphere always has the CD of a sphere, no matter how big it is.

Mm-hmm. . And so you can scale

[01:28:52] Randall: So scale, scale and variance essentially to be a

[01:28:55] Josh: Exactly, Yeah. And so then the A is the area. And so that's times, and that's the scale. So it, it's just a way that we talk to each other cuz it's simpler. Um, and, and, well it's,

[01:29:05] Randall: it's just really is true. Like it's teasing out the thing that's most relevant too.

It, what matters is, is uh, yeah. If it's scale and variant, if it's a scale and variance effect, then you'd only need the Yeah, that makes sense. So CDA and what was the other one? The other term?

[01:29:21] Josh: C r which is coefficient of rolling resistance. Okay. Um, and, and that's same thing that that's, that's a true one-dimensional and it's just a coefficient.

The problem with CR is it's got so many, it's like point when, when we people talk about it, they're always like, it's 0.0, zero, zero, Like people's eyes roll back. Um, and, and it also makes them seem like very small numbers, but when you work them into math eight, It can turn out to be a pretty big number.

Um, but anyway, so Rob, Robert has this idea of how he can find, solve for these two, um, in a situation that he otherwise knows nothing about. And he, from like Strava data on the web realizes he can kind of do it. And so he gets with some other smart people and ultimately they, they develop, um, the, the calculations here and there.

There's a free online tool called Golden Cheetah that you can use to solve, um, to solve for it. And, uh, yeah. And so we, we've used that for God, 10 plus years. And, um, we do a ton of these for, for teams and riders and athletes. And, and the tools have changed, but you know, the numbers kind of stay the same. I mean, we're, you know, we're doing it now on laptops and, and phones and, and the power meters are much more accurate.

But, um, you know, the, the outcome outputs haven't changed all that much. And so it hit me a couple years ago that like, wow, we've. You hear Google and Amazon and these people talk about how, like, how valuable the data is. Like, wow. I think we're sitting on something really valuable, which is that we've got 4,000 real world tire optimizations where we know the tire width, the rider weight, the rider weight distribution.

Mm-hmm. , the surface roughness and the pressure that was the fastest. Right? And so, you know, when you think of, uh, the graph of the rolling coefficient rolling resistance for a tire, it, the challenge we've had for the last 30 years was everybody's mental model of, of what that graph would look like comes from lab testing and, you know, you put a tire on a smooth steel roller and you get this like dropping, uh, line that asymptotically approaches some number as the pressure gets higher, right?

And so mm-hmm. , you just look at that and go, well, higher pressure is faster done. What we've learned in the real world once we had the techniques to do it, is that that curve shape is actually something like a v You know, at some pressure that line kicks up again and the resistance starts to get up. And that's cuz you're now vibrating and, and lifting the bike and the rider system, um, you know, up and down and shaking them to deal with the roughness, the, as the tire gets harder.

Um, and so what our data had was thousand, literally like over 4,000 optimizations where we had solved for that break point, right? The bottom of the v the peak minimum rolling resistance mm-hmm. for a weight and a tire size and a surface roughness. Um, and so I thought, Oh wow, I, I bet we could put this together and start to kind of draw lines of correlation like Sure, you know, rider of this weight across surfaces, across tire widths.

And, and so what our calculator does is it in actually a very simplistic way, it puts all that together and then draws, um, Really lines in between them, right? So we're, we're essentially making curves to fit. You know, a rider of your weight has a curve that looks like this on this tire, and on this tire it looks like this.

And that's all coming from real data, but it's all very simplistically done, uh, when you really get in there and look at it. But we're able to interpolate the missing data points. Um, the other thing that's fun with, with our calculator is like, you know, if you know Peter Sagan's weight on the day that he won his rub and his measured tire width and you plug that in there, you'll get the, you'll get the air pressure that he rode.

Um, cuz cuz that's also how it works, right? Mm-hmm. . So, so there's some, there's some fun gems in there if you, if you know the, the right numbers to key and you, you can get to some really cool little, uh, little things. But, but yeah, we're, we're essentially just saying, Hey, this, this is what's proven to be fastest in the real world and so we're just gonna give it to you in a way that, you know, it's takes 15 seconds to calculate your version of it or,

[01:33:34] Randall: And this is for anyone listening.

We'll put a link to that in our show notes as well. Um, we actually link to your calculator, um, on the, uh, in our FAQ for, uh, logo's components, uh, just because it's so well done. Cool. Cool. And, um, just to bring this and we'll, we'll close up with this, but, um, so if you're using that calculator, um, I want to kind of tease out how to apply it.

So one way to apply would be just take the numbers and put 'em in. And I think that that probably works really well for a more controlled environment like road. Um, but say gravel, you have a lot more variation, which you've taken into account in your calculator, but. The rider's technical ability, plays subs substantially into the offroad experience and even equipment choices, like a, a drop post that allows you to have, you know, different weight to shift your weight distribution, to have, um, you know, more travel between your body and the bike.

So using your arms and legs is suspension and, you know, if you ride loose versus riding tight, all of these are gonna come into play. And so, you know, you can start with these. I guess my, my perspective, and I'm curious yours on this, is particularly for more technical gravel situations, use it as a starting point, but then find the one that makes you feel most confident for the train that you're riding.

Mm-hmm. . And then maybe bias, you know, you might go slightly lower to get more. Traction or push or whatever it is you're after, you know, pushing, you know, obviously with the limit of not wanting to bang your rims against rocks, uh, but you know, there's a certain technical competency that's required, uh, uh, technical elements and writing style elements.

That's, um, seems, I, I don't, it seems to me more relevant and gravel though, though. You tell me, uh, you, you understand this a lot better.

[01:35:25] Josh: Oh, I, I think there's a, a, a ton of truth to that. I, you know, I think the, the couple, the couple of blind spots we know exist in the calculator, the, the biggest one is that, you know, the, these data points come from, I mean, really the fittest athletes in the world.

Yeah. Yep. And, and they're in most cases riding like the fastest, most supple tires. Yeah. And so a couple things that we know, you know, that the, when you hit the break point, it's because the energy lost to Thetas, right? Or the, um, the inefficiencies of shaking the rider have become greater than the casing losses, uh, of deflecting the tire.

Will, you know, the, the fittest athletes in the world at two and a half percent body fat, their a lot lower ESIS than me. . Mm-hmm. . Mm-hmm. . Yep. Yep, yep. So, so if you're, if you were less than the fittest athlete in the world, you were a higher ESIS individual, some of us jiggle more then Yeah. Some of us jiggle more.

Um, and, and so that, that likely will shift your optimal pressure potentially downward, right? As your body fat goes up, that that optimal pressure probably drops. Um, you know, as tires become less supple, um, they have their own. Added hysteresis, which causes a dynamic stiffness problem in high frequency vibration.

And we could do a whole episode on this. It's pretty fascinating, uh, that I know. I think we were the first to really discover and try to like, explain it and quantify it, but, um, You know, static stiffness, like you just push on a tire to pressure, they all look the same. Mm-hmm. , but dynamic stiffness, like stiffness under high frequency vibration.

Oh, you almost get

[01:37:04] Randall: like a ding effect. Yeah. With a stiffer side wall. So the can't respond as quickly.

[01:37:11] Josh: Exactly. Yeah. We, we describe it as being a lot like, um, packing a suspension fork. Yeah. On a wash board. Yeah. Um, or, you know, my favorite analogies are say like, you know, you, you see the um, uh, memory foam mattress commercial where they press the hand in and then they remove the hand and in print stays, you know, that's histories this, Well, think of that now as like a memory foam punching bag.

Like if you just keep punching that same spot. Yeah. It down compact itself. Into like a rigid, it's

[01:37:37] Randall: not even phone. Oh, it hadn't occurred to me that that would be relevant in a, like it'd be a significant, a sufficiently large effect in a tire in order to be relevant though I guess you're dealing with super high frequency vibration.


[01:37:49] Josh: Yeah. And it's, it's actually one of the reasons that, that people can feel crappy tires. Yeah. Cause you think, like in the lab, you know, 20 years ago you would inflate a tire push on it with a, an anvil and go like, well it has the same stiffness as, you know. So we used to assign casing stiffnesses like, oh well that has a 0.2 psi casing stiffness.

There's no way you can feel that. Well, you draw theta curve and then you look at the time response. And this is a podcast, so I'm using my hands cuz we're on video. But you know, if you've got a 45 degree slope in your outbound, uh, you know your compression pathway and then your hysteresis drops like this well over certain time frequencies, your.

Um, your stiffness becomes like a line that's connecting the two, the bottom, and so it can become damn near vertical. Um, again, you gotta, I wonder this must you to a blog post to, uh, to understand that, but this is why people stuck with Tubular so long behavior can be No, that was more tradition and pressure, but I, I think it's, um, Okay.

It's, it's one of the, it it ultimately becomes, one of the reasons that people stuck with high pressures for so long, um, is that they equate those high frequency vibrations with speed. Yeah. Yeah. That's not true. I, I made that mistake. Um, and that, and that also makes you not feel that crappy tires are slow because they feel fast, because they have a lot of high frequency vibration.

Right. And so mm-hmm. , you know, you think of like trying to convert people from. You know, poor tires to, to fast tires. They, they might say, Well, it doesn't feel fast and it, it's too comfortable. Or it's too, you know, it's like, well, well it's just not beating the crap out of you cuz it's a, a better tire. But you, we now have the tools that you can see that that's quicker.

But that, but that's another, um, and we've, we've now added a, a compensating factor for that in our calculator. But, you know, if you're training on, you know, armadillos, um, you need a, you need a different optimal pressure than if you're out on your GP five thousands. You know, it's just because of, again, the static stiffness may look similar, but the dynamics stiffness can be quite different.

Yeah. And of all

[01:39:56] Randall: the things that you can do, so those look like, like tires and like tubeless tires and, you know, you can't change your rims without changing your wheels. So tubeless tires being in, but the more supple casing and will, uh, of all the things that you could do to improve your right experience, that's probably highest on the list if I had to guess.

Bike fit

[01:40:14] Josh: the other one. Yeah, a hundred percent. Yeah. Yeah.

[01:40:16] Randall: Um, we could go all day. This has been absolutely delightful. Maybe if you're interested, have you on again in the future to dive in, uh, on some of the questions that emerged from this conversation. I know that we had, a number of listeners who had posted some questions that we didn't quite get to.

Hopefully we covered things sufficiently here, but Josh, this was a hell of a lot of fun. Really appreciate you joining and let's keep in touch.

[01:40:41] Josh: Awesome. Really enjoyed it. And yeah, let's do it again.

That's going to do it for this week's edition of the gravel ride podcast. Big, thanks for Randall for taking the hosting duties and having that great conversation with Josh. I hope you enjoyed it and you will check out everything he and the team are doing over at silica. Big, thanks to logos components for sponsoring this week's episode. We could not continue to do what we do without support from companies like logos.

If you're interested in connecting with me, I encourage you to join the ridership. That's It's a free global cycling community where you can connect with gravel, cyclists from all around the world. If you're able to support the podcast financially, please visit buy me a gravel ride. Or if you want to just do something, that's a solid for me, leave me a rating or review. It's usually important for our discoverability that we get new reviews in there. And I hope you're enjoying everything that we do and put out there each week. Until next time here's to finding some dirt under your wheels