Lennard Zinn and the Art of Tire Pressure

In episode 95 we explain the complexities of the tire, tire pressure, and how those things lead to changes in comfort, grip, rolling resistance, and more.

Lennard Zinn Fast Talk Podcast

Today in episode 95 we talk in-depth about the humble tire. Often neglected, frequently misunderstood, the lowly tire is a much more complicated piece of equipment than many people know. Today, with the help of two very talented technical gurus, Lennard Zinn and Nick Legan, we explain the complexities of the tire, tire pressure, and how those things lead to changes in comfort, grip, rolling resistance and much more.

Let’s make you fast!

Primary Guest Lennard Zinn: world’s leading expert on bike maintenance and repair
Secondary Guest Nick Legan: Shimano road brand manager

Episode Transcript


Welcome to Fast Talk, developer news podcast and everything you need to know to ride like a pro.


Chris Case  00:14

Hello, everyone and welcome to Fast Talk. I’m your host Chris case. Today in Episode 95. We talk in depth about the humble tire, often neglected, frequently misunderstood. The lowly tire is a much more complicated piece of equipment than many people know, today with the help of two very talented technical gurus, Leonard Zinn and Nick leagan, we explain the complexities of the tire tire pressure, and how those things lead to changes in comfort, grip, rolling resistance and much, much more. So, get your silk tubulars ready, but whatever you do, don’t pump them up to 180 psi. Let’s make you fast.


Chris Case  01:05

Well, it’s always a pleasure to have you in the studio with us, Leonard, I like to call you a legend. And that’s because you are a legend. And you know so much about so many things in the bicycling world. Today, I know this is going to be at times a little technical at times, hopefully a lot practical. It’s something that you in a sense research for years, both in Finland in the microbiome laboratory right down the street from us. So you have a wealth of knowledge on the art Zin in the art of tire pressure is what we’re calling this episode. It’s all about how pressure inside the tire affects everything from comfort to speed to ride quality. There’s the physics of that there’s the practical nature of that. So we really want to dive into that topic. For those of us who ride cyclocross, I think the effects on ride quality and grip and all these things are readily apparent based on tire pressure. Because we mess with it a lot we run with, we run really low pressures. So people that are comfortable in that space, have done some cyclocross and have played with that know a bit about what we’re talking about. I think there’s a lot of other people that don’t do that, or are sort of like limp 110 psi on my 23. That’s the way to go sort of stuck in a in a rut or stuck in that mentality. So we want to break some myths today. We want to just open people’s minds and hearts to the art of tire pressure.


Trevor Connor  02:45

Right? Ray said stuck in the mindset of 110 psi Lennar and I can both talk about the days and people were looking for tubulars that could pump up to 180. Because 160 wasn’t enough. Well, there’s


Chris Case  02:57

that too. Yes.



Yeah, I pretty much always used silk tubulars at 135 psi. I thought that was the thing for racing. I raised all kinds of big races with that. And God when I think about how much harder I was working when I needed to


Chris Case  03:17

now seems like you are at at at effectively defeating the purpose of running a nice supple tire. I



was Yeah, that’s exactly right.


Chris Case  03:26

Yeah. So you’ve got all that silk there and then you basically turn it into concrete.


Trevor Connor  03:32

knock your teeth out. That’s right.


Chris Case  03:35

Most people probably don’t really think too much about tires. They think, Oh, I put it on my wheel. I pump it up and I ride. But they’re actually a little bit more complicated than that. And there’s a lot of variables involved. There’s the construction. There’s the width, there’s the tread pattern, there’s the the the construction effects, a lot of things because it has to do with whether it’s not only are we talking tubular versus tubeless versus tubed or clincher, but vulcanized versus non etc, etc. So just give us a sense of how actually complicated the tire is.



Well, yeah, the tire is pretty complicated. It’s made up of many parts of the casing and whatever is constraining the, the air inside, whether it’s an inner tube, or if it’s a tubeless tire, if it’s just a thick coating of rubber on the inside of the casing or that with tire sealant sloshing around in it. Then you have the tread itself and how it’s attached to the tire and what the tread is made out of there. engineers that spend their whole careers just mixing different things into latex or into a synthetic rubber compound to turn and reduce the the energy loss and it reduce the hire



nerds. Yeah, retire nerds in this world. Yes.



tread tread tread down. Yeah. And, and, and that, that can be a big deal, the average person is not going to be sensitive enough to, to really be able to tell fine differences between between rolling resistance of different tires. So it’s kind of easy to just keep just oh yeah, I just put my tires up and go. Until, you know, it’s pretty obvious to you, if you get on a mountain bike with, especially like a fat bike with like four inch tires on it, and you go riding down a smooth road, you’re clear, you’re working a lot harder rumbling along with that, then when you’re on a really nice tire on road bike, and it’s not, I’m talking also at low speed where it’s not just an aerodynamic difference, but but really the just the rolling resistance, you can feel that when it gets finer and finer. I mean, people roadies could be familiar with you know, their their tires that are made to really, completely be resistant to, to puncture. So they’ll have the lava casing made out of an aramid fully aramid casing, which basically means that the tires, the casing is made out of Kevlar instead of out of cotton or nylon are one of the other the other materials that’s used to make the casing with and Kevlar is just some really stiff stuff, you’ve got this Kevlar fibers and maybe that benefits you if you’re in a place where you’ve got a horrible problem with thorns and in the end, you’d be faster because you’re not stop and fix your tire all the time. But, but really the tires like that holy smokes most you know, people that ride a lot can tell the difference between riding one of those tires, puncture proof tires, and riding a nice tire and or a solid tire, for instance. That’s another example of a tire that really slow to roll.


Chris Case  07:11

Yeah, and all of these things that we’re talking about the construction, the width, the pressure, they all they go hand in hand with. And it’s a balancing act between comfort, speed, durability, ride quality, all of those things. So that’s why I say it’s, it’s complicated, it’s you could just, and a lot of people don’t just get any old tire, put your Gator skins on there, that will never puncture. And they’re fine with that. That’s great. But there are tires that will make it. It’s like an entirely different world, when you get on a nice supple tire and have it at the appropriate pressure, and width and all of that. And it’s like a glorious thing.



And it’s much easier to keep up with your friends.


Chris Case  08:00

Well, there you go, yes, you don’t have to have an E bike at that point to keep up with your friends just use better tires. Okay, Leonard, I think it would be helpful for you to define some terms related to tire






I think one that’s critical with with talking about tires and tire performances to discuss history says anybody that’s taken elementary physics has run into it, but it usually wasn’t talking about rubber. It was talking about magnets, magnetism and the oblong curve that is created by history Sis, which has to do with basically a lag between the applied force and the resultant action. And in the case of rubber, it’s because it’s an elastic material. And when I say rubber, I’m referring to tread compounds. And I know, companies want to talk about their proprietary tread compound and whatever, and it’s not rubber or whatever. But basically, it’s rubber.


Chris Case  09:07




when you apply a force to rubber, there’s this delay because it’s elastic. Once you’ve pushed it far enough, then it starts moving. But then when you release the force, you don’t get all the energy back. There’s a delay in returning and so history says curve instead of being like a line that goes out and come straight back on the same line, it follows two different paths out and back, creating a loop creating a loop and that loop. The wider that loop is, is the greater the energy loss in that in that cycle. And so when the tires rolling along the ground, that’s there’s this lag between the tire reacting to the force The ground up is applying on it. And then there’s a bump or some some Yeah, hitting the surface, even just the asphalt, you know, there’s all the little red little particles in the asphalt that are all stuck together. And just in, in conforming to those, and then, and then returning to its original shape each one of those back and forth, there’s a little bit of energy loss. And obviously, if you’re trying to propel a bike the most efficiently, then you’re trying to minimize any energy loss as you can. And that’s one of them. The root word here perhaps is


Chris Case  10:43

hysteria. Does that does that? Does that? Does that help people envision what’s going on inside a tire? Perhaps I don’t know. I don’t even know if that’s, that’s the correct root word. But to me, it makes me think of hysteria or hysterical, like, there’s a lot of confusing energy going on inside a tire if you continue to have it hit up against obstacles of one size or another. That’s kind of how I envision this because it’s a technical physical process. But if you just think of sort of, like asteria, maybe it makes a little more sense to people. How does how does that relate to internal friction?



Well, sort of one in the same thing, history. So it’s an internal internal friction, that that’s, that’s the frictional resistance of a tire rolling without slipping is all about it, there’s, there’s all these parts of a tire, you have the casing and the tread compound. And, and, and if it’s like a handmade tire would be glued to that casing. Whereas a vulcanized tire, the whole thing is all is all molded together in one piece. But you’d have this interaction between all those things, there’s history says in the tread compound and the rubber tread, but there’s also there’s also energy loss in the in the deflection and return of the tire casing, the threads are all either stuck together very tightly in a vulcanized tire or they’re more free to move independently. And and if they’re, if they’re finer threads, then that those are able to move with back and forth with less, less energy loss than ones that are big and thick that it’s not only more mass, but they’re but they’re just stiffer, so to make the move, and then and then they’re coated with rubber. So returning that whole elasticity histories, this loss as part of that. So that’s the internal friction that we’re talking about really is that history says curve.


Trevor Connor  12:54

So I don’t understand the science nearly as well as you but the way it was explained to me that I kind of had a high kind of get that is there’s a contact area with the ground, how much of the the tire is actually touching the ground at any any given point. And that contact area is actually remarkably consistent, whether you’re using the 2123 25 seat tire. So if you are using a narrower tire, there actually needs to be more deformation of the tire to get that same contact area with the ground. And every time you’re deforming the tire like that, as you said, you lose a little energy. After the tire, that part of the tire leaves the ground and tries to return to its original shape.


Chris Case  13:41

Think about if you were to zoom in on a tire that’s pumped up really hard, and it’s going over a rough surface, then the the the tire is not deforming to meet that obstacle in such a way so that the bike is having to travel up and over each one of those things more so than if you’re writing a tire that’s wider or lower pressure and is able to absorb those things. And you’re going to get to this term to the sprung weight from weight isn’t having to be lifted over each of those bumps with with every time the wheel hits. And one of those small obstacles again, for zooming in on this tire as it hits the ground, or a rock or a pebble or a divot, or whatever the case may be, again, if it’s really hard, it’s traveling up and over every one of those little things more so than if it’s just kind of smashing it absorbing all that stuff.



Is that right? Yes, that’s right. And, and I think it’s an easy way to, to think of it is to think about it on a much bigger scale, and think about suspension. So on a mountain bike, I think everybody that’s written a mountain bike A lot has a very clear sense of how they get up, they if they’re going to go down a steep super rough trail, and they’re on a bike with a lot of suspension travel, first of all, it’s a much smoother ride going down. And when they get to the bottom there, their wrists and shoulders and arms and triceps aren’t completely beat, they don’t have that itchy feeling of their arms from having the right try to control it the whole time. But they also generally would go faster because the tire, the tire is able to stay on the ground the whole time. And, and, and the person isn’t having to absorb all of this energy of the bike coming up and going back down and open down. Instead, the only thing that’s going up and down the sprung weight is now much lower percentage of the entire weight of the bike and rider the sprung weight is now just the front tire, I mean front wheel, and the lower part of the fork that moves up and down on the fork stanchions. And in the rear, it’s just the rear wheel and the rear chainstay the the swing arm as we call it, moving up and down. And so that’s a much smaller amount of mass that goes up and down, then the whole bike and rider so less energy is lost with, you know, the same amount of gravitational forces working on the bike and rider but the bike and rider go faster because there’s less energy loss and bouncing the whole thing up and down. And when you then think of Okay, well, what about uh, about a fat bike people that are familiar with fat bikes, you can ride a fat bike with like five inch tires, and no suspension, you can go pretty fast on one of those was really, really low tire pressure, like four psi or two psi on a rough surface. And because the sprung weight is now only the amount of tire that moves up and down until until the size of the bump exceeds, you know, probably half the half the width of the tire, then then it lifts the whole bike and rider and so it’s not going to be as fast on a really rough course is a fully suspended bike, but but you can get the sense of how just this little amount of rubber and casing material is moving up and down and then the rest of the bike and riders just going in a straight line. And so then on a road bike that is also happening, it’s just on a much more microscopic scale where, where you have the tire absorbing the little imperfections in the road or not. And then when you go to the opposite extreme and you think of like you’re riding on polished marble or glass, then the fastest thing is going to be have your tire pumped up really, really hard there then then what you’re trying to do is, is minimize the length of this of the contact patch so that there’s less deflection of the tire and then you have less energy loss, then if you if you have a softer tire, and then every every bit of tire that rolls past has to squish down considerably more in order to make that contact patch. Bigger, like I said, because the number of pounds per square inch is lower.


Chris Case  18:14

That’s why track riders still would run really high pressures, because effectively the the surface of a track most tracks most good tracks is very smooth. Not that marble smooth but close to it. Yeah, that’s right.



And that’s why they use smaller tires to smaller, you know, little tiny 19 millimeter tires or something like that. Also, because they don’t have to, they don’t require this bigger contact patch in order for cornering. Because on a track, the banking of the track does the cornering for you are essentially riding in a straight line, you don’t have to


Chris Case  18:50

have to deal with that. Getting into the the practical side of this. Let’s talk a little bit about what this means in terms of rolling resistance, for instance, speed, comfort, these types of things. How does pressure affect those attributes?



Well, I think everybody has a sense that the lower the pressure you have, the more comfortable the ride will be. And where you wouldn’t notice a difference is similar like when we what we just talked about. If you’re riding on polished marble or glass, there would be really no difference because you’re not getting bounced around. Even at really, really high pressure. Your comfort is related to how much you’re getting bounced up and down. And you know this whole thing where, you know, when I was a little kid and you’d see runners, the fastest runners in the world and in the Olympics and the hundred meter dash, they’re just wearing little short, loose shorts, and now they’re all wearing like really tight, long lycra, lycra shorts. And the idea is to minimize the vibration of their muscles and and and that they’re that they’re more efficient, the less their muscles are getting bounced around. That same thing applies on the bike. And so comfort is, I think that’s a pretty good gauge of that it’s pretty directly related to efficiency of the bike moving down the road or trail.


Trevor Connor  20:34

Chris sat down and asked Shimano is road brand manager Nick league and his perspective on tire pressure.


Chris Case  20:41

First thing I want to ask you, since you have so much history as a mechanic, working for the best in the world at the pro tour level, for some really big teams racing in Europe, who probably have some bias towards what they should do with tire pressure, all the way to today, that’s, uh, almost probably two decades of evolution in how people think of think about tire pressure, how have you seen the thought process change around that, you know, very particular subject.


Nick Legan  21:16

It’s absolutely changed. And I would argue that, in fact, my world tour experience was kind of prior to some of the more recent learning on CRR rolling resistance and really data driven decisions. I think Josh portner, you know, his Soca has done a lot of research in this in this realm. Tom aanholt has done quite a bit of rolling resistance testing. And I’ve followed that with fascination. You know, when I was a pro mechanic, we we ran pretty high pressures. We ran two boilers all the time, you know, we now know that in a lot of instances, a clincher tire or tubeless tire can be faster. We now know that wider tires can be beneficial, right? I’m not going to say always. And we also know that tire pressure that the brain can can misconstrue sensations that we feel when riding a bike as fast, right? And that’s not necessarily the case, essentially, what the way I look at it is, if you feel your tire doing something, it’s probably not at the right pressure. And when it disappears, you’re probably getting closer.


Chris Case  22:22

mm optimal. When it’s more supple, and it’s absorbing a lot of that surface, whatever that surface might be a rough gravel. road that isn’t as smooth as you really think it is. That’s


Nick Legan  22:34

why kinky mountain bike doesn’t matter. They’re certain that same could could be said for your car tire, motorcycle tire, you name it.


Chris Case  22:40

Yeah. So you have followed this evolution and this recent uptick in research and thought put into tire pressure.



Absolutely. What


Chris Case  22:53

then do you recommend to people as they try to think about this, as they’re learning themselves what to do with tire pressure?


Nick Legan  23:01

Well, the first recommendation I would make is, don’t buy a thing. Don’t spend another dollar, right, until you spend some time actually approaching this scientifically. You know, you can do what we call bracketing, you know, where you try it at the highest end, at the lowest end, and then you find the middle, you know, you break it down, in in on what’s probably an optimal or at least a better pressure for you. And then


Chris Case  23:24

kind of like sorry to interject, but it’s not unlike when you’re taking back in the days when you used film in a camera, you would actually you would bracket the exposure, you maybe go a little over, you’d maybe go a little under and then somewhere in there, you’d hit the right exposure.


Nick Legan  23:40

That’s exactly it. And that’s where that’s where I learned the terminology. Yeah, that’s how old school I am. Yep. In terms of Yeah, developing filament in the gas actly. Similarly, that with your tires, I think the other thing to have a good understanding of is what what are you bracketing towards? What’s the end goal. And if you’re just looking, let’s say, for better control of your bicycle, if you’re racing criteriums, for instance, cornering prowess, might Trump the best actual rolling resistance number for you, right? If you’re looking at gravel, maybe it’s a comfort thing, or mountain biking, you know, it can be more comfort driven. So none of those things are superior to another. If you’re doing a time trial, it’s probably rolling resistance is what you’re really see your speed. Absolutely. So have an understanding of what your what your goal is, and then go about figuring it out. And then once you start doing some of that bracketing, you might realize that, that the product you have on your bicycle might not be best for you. So it might mean a wheel change, because maybe you want a wider rim. Maybe you want to go tubeless where you had innertubes before. There are a lot of decisions then that can follow from that.


Chris Case  24:47

It’s kind of amazing how complex this can get in a lot of people don’t think at all about tires.


Nick Legan  24:56

Yeah, but it’s but it’s one of those things where and I and I’ll I’ll repeat it. Don’t buy anything, used things you already have to get better to find something that’s better for you


Chris Case  25:06

make informed decisions is what you’re getting at. But so, in a nutshell, isn’t it?


Nick Legan  25:11

I hope so. Let me think on that for a second. But I think more than anything, I think it’s really easy to underestimate the effect that tire pressure has on your cycling experience. Yes, it’s massive. And again, you don’t have to spend a dime. In fact, you might have to do less work by running a lower tire pressure than you do to pump that thing up. rock hard.


Chris Case  25:31

Yeah. I hate to call it a bias. But I know that you are one of those people that if you were in a group on a group ride, and you went around and you use your thumb to give it the the pressure, check with your thumb like people do. Yeah. People would be like, man, Nick, you run your tires low.


Nick Legan  25:50

I do. Absolutely. I’m, I’m a fan of big tires. I’m a fan of lower pressures. for lots of reasons. One, I’m 155 pounds. Mm hmm. I’m not a heavy writer. I have knock on wood. Very few flats in a given year. Mm hmm. I don’t I’m just not hard on equipment. Yep. So for me, I don’t see why would I create more vibration into my system? You know, this is Fast Talk you guys have talked about, I’m sure the effects of vibration on muscular musculature, right and how it creates fatigue yet, so I’m also not that gifted. So I got it. I gotta pull it alpha stops, man. I’m gonna wax my chain. I’m gonna keep my pressure lower. So I can just hang with the group. Yeah, you know, right. So, but I do I run lower pressures. I mean, it’s rare. It’s at this point, it’s rare that I ride a tire because I’m not roadracing. To put that out into the world. I’m not road racing anymore. I’m not criterium racing. I’m riding the road. I’m writing a lot of gravel. But a 32 mil tires about the smallest tire I write anymore. Yeah. And I just massive compared to what most people have in there. I had 18 millimeter tires when I was a kid. And I was like, Oh, I’m going so fast.


Chris Case  27:00

We did. We thought that when we spoke with Leonard, there was there’s this mindset, you have to overcome hard equals fast when, like you were saying earlier, if you feel if you feel your tire doing something, that’s probably too high of pressure, whereas it used to be back in the 70s, when when Leonard was at the peak of his racing career. Like if you felt every single vibration coming through that bike, you felt like you were flying?


Nick Legan  27:30

Well, it’s that high frequency. Yeah. And we our brain associates that with speed. Mm hmm. And it’s and it’s, it’s, it’s our brains trumping us up. But even when I was running, let’s say 25, or 28, I rarely saw at psi as a very specific example. But these days, I rarely see 50. Yeah.


Chris Case  27:46

So would you say there’s as much art as there is science to this still?


Nick Legan  27:53

There is to some extent, because I don’t have a lab. You know, I’m not I’m not doing roller tests, like Tom on hold. I’m not sending things to Finland or whatever for that. Yeah. Yeah. Yep. Wheel energy wheel energy. Exactly. So. And I think where the art comes in, is a bit with, you know, it’s one thing to talk about rim with, it’s another to talk about tire width, but then you still have tire casing differences. Yes. So I was having a conversation last night with a sponsored athlete for Shimano. And that athlete, we were discussing some different tire options for gravel that that athlete is considering for the next season. And he was experiencing some burping on this given tire with our rim. And what we, I kind of pointed out was that that particular tire, and I don’t want to name names in this case, but it was it’s a really, really simple tire. Mm hmm. So for the same feel, or the same, probably rolling your distance, you can run that pressure a little higher on a really high end supple casing tire, right, versus something that’s a little more kind of a garden hose. He, you know, he has something that’s just a little more durable and a little less flexible. Yeah, and probably has a longer wear, like a longer lifespan, but it’s not as much of a performance tire. So to get the same kind of equivalent feel, and handling characteristics, the tire pressures will be different.


Chris Case  29:09

Yeah. And I think that’s where some people get tripped up is that you have to consider all of these factors when you’re making your, the optimal choice is not it’s not just about pressure anymore. It’s about casing, it’s about width, it’s about rim width, it’s about surface, it’s about all of these things and trying to bring all that information together to make the right choice.


Nick Legan  29:30

But I would also say don’t I mean, it is complex, complex, especially when you start talking to Leonard about all the math. Yes, yeah. I mean, he goes all Los Alamos on it, you know, he’s incredible. But he’s also really good at boiling it down and saying, don’t let that stop you from experimenting, though. Like this gives us this opportunity. Most of us ride. Well, I hope we all ride five plus times a week. But each one of those is an opportunity to try something so there’s there’s no reason not to experiment.


Trevor Connor  29:58

Now, back to life.


Chris Case  30:00

So there’s one other definition that we haven’t spoken about. It’s another cool one. It’s another physics lesson.



hoop stress hoop stress has to do with the relationship between the size of the air chamber and the force on the walls of it. The stress on the walls of it. So actually a good example is a is those those inflatable tennis courts those those tennis courts that have a big dome, well, yeah,


Chris Case  30:28

like the Okay, the bubble place where you would go inside. Yeah, and play tennis. Yeah, exactly. And, and those things are a soccer field or a track these, they look like the Michelin Man blown up on



Yeah, and they’re blown up. But you go in there and you don’t have the sense your ears don’t start popping like crazy and everything, you don’t have the sense that it’s a lot higher air pressure in there, in order to keep this thing inflated. But you do know that if you were to blow up a much smaller thing, a balloon, for instance, that it’s going to take a lot more pressure it would be that would be something that you would if you were to somehow be able to climb into that balloon your ears and pop like crazy, because you would be aware that it’s a lot higher pressure in there but but the bigger the surface is the the amount that it that inflates is related to the stress on each square inch of it, when you have a huge surface the the stress is much higher for any given pressure change the bigger it is. And and another way to think of it as a is a vacuum chamber if you were to suck the air out of a small thing you have a I used to There used to be a museum and the town I grew up in where they would create little little vacuum chamber out of aluminum foil. And when when they grew up in a strange town. Yes, I grew up in Los Alamos New Mexico.



vacuum chambers laying around on the streets Exactly.



So if you were if you suck the air out have to go to like literally zero vacuum on a small thing, let’s say the size of a cigar to the cigar cigar tube, you could probably suck all the air out of that cigar to with the aluminum cigar tube, and it’s not going to collapse. If you have something the size of a house and you suck all the air out of it. The walls of this house are going to have to be super super super thick to not collapse in because because of this hoop stress thing where you were the amount of force the stress on on on each individual square inch of it is related to its diameter. It’s proportional to its diameter. If you’re thinking of a cylindrical or spherical thing, when you have a if you have in when we’re talking about tires, if you have a tire that’s a 19 millimeter tire say and you pump it up to



100 and



say you pump it to 150 pounds per square inch, it’s gonna feel quite hard. If you have one that’s twice as big, so 38 millimeter tire. If you pump that up to 150 psi, it’s now got double the diameter and the hoop stress is double so the amount of stress on each fiber in there is twice as high you know that 150 psi on 19 million retire that’s starting to push the limits of it. Well, if you put 150 psi on a 38 millimeter tire, don’t do it don’t do it. It’s gonna it’s hoop stress is so high even though the construction can be exactly the same, exactly the same, same material, same construction type, same thickness, everything that tire will fail or if it’s a clincher it’ll, it’ll fall the walls of the of the rim out and just blow it right off of the rim. So if the 19 millimeter tire you’re running at 150 psi, then with 38 millimeter tire, you’d need to run that at 75 psi that would be exactly the same hoop stress so the tire is just as hard rock hard rock hard at 75 and there’s no reason to go any higher. If you want the tire rock hard your 90 millimeter tire was rock hard at 150 well it’s gonna be rock hard the 38 millimeter at 75 and then you know if you go what’s twice 38 is 776 millimeter tire which is which is three inch, that three inch


Chris Case  34:44

like a 29 plus tire



plus tire. So that would be have to be half again, which would be 37 psi would be rock hard.


Chris Case  34:53

Yes. That’s why you can get away with I mean not get away with but that’s why in a fat bike. You’re running a five inch tire for psi is is sounds like oh my God, that’s nothing but it’s plenty. Yeah. And the stress on the, the hoop stress is actually something inside that tire for is a small number, but the hoop stress is plenty, it’s not going to roll off the rim, you’re going to have a good amount of suspension and traction and all of that. So it’s, it’s this proportional amount of stress for the given width of a tire. And those two are related. Yeah, I


Trevor Connor  35:33

was shocked the first time ago on Fat Tire bike, the guy at the shop is debating, should we pump you up to three psi or four psi. And all I’m thinking is, I think my pump at home starts at like 10 psi.


Chris Case  35:46

That is that is the problem with that, but you need a different pump or a different gauge. So



related to the width, you have to adjust the pressure based on the width first, like we discussed earlier, we’re talking about hoop stress, the bigger the tire, the lower you have to run the pressure in order to just maintain the same hardness of the tire. If you’re writing criteria, you know, I’m aware that when I was serious about racing in the early 80s, that the pros like in the Tour de France, Greg Lamont, I remember him crashing in the critical time trial and final time trial, the Tour de France when he was trying to take down Bernardino and succeeded in doing that. He crashed in that time trial, he was running 19 millimeter tires at ridiculously high pressure. But this is a European course with sharp corners going through little towns and stuff like that. And we all thought, harder tire that smaller harder tire, that’s going to be the fastest thing. It’s definitely the lightest thing to have a smaller tire because rubber is dense, it’s heavy. It’s definitely not the fastest and it’s should be clear to anybody that’s not the most traction on a on a sharp corner. And I’m pretty sure he wouldn’t have had that crash in that little town. Come making a sharp turn at that high speed if he’d had, you know, say 23 or 25 millimeter tire and would


Chris Case  37:09

know what in their right mind would run at 25. back then. Yeah, no racing cyclocross on 25. Yeah,



that’s right. I when I first was racing, when I raced cyclocross nationals in 1988 28 millimeter tires,


Chris Case  37:23




It should be clear that if you’re riding a criterium, a bigger tire is going to give you more traction on the turns and criterium is very based on the cornering. And if you can take the corners faster, you have to do less accelerating afterward, you’re going to expend less energy. And so that’s the first thing. So body weight, and then body weight. The heavier you are, the higher the pressure you need. Because what we’re what we’re again, what we’re talking talking about is say we want a certain total amount of surface area on the ground of the tread patch. And so the bigger you are, the more the tire squishes out when you sit on the bike with the same amount of pressure in the in the tires, the heavier You are the the higher the pressure you need. Conversely, the lighter you are, the lower the pressure you run. And so if you’re, say 150 pound rider doing a criterium on a pretty smooth road, well, I’d say a 25 millimeter tire. Now we’re talking about if we talk about hoop stress, so if you if, if this person, say would normally ride 23 millimeter tire at 90 psi, well now 25 millimeter tires, what percentage bigger is that that’s two out of 25 is 8%. Bigger, right? So, so right away, you have to go 8% lower, so the 90 psi now becomes 82 psi, they just have the same amount of stress the same hardness of the tire. Mm hmm. And so so right away there, if you’re going to 23 millimeter tire, I’ve pretty smooth road, I’d say that would actually be a pretty good setup for a guy at 150 pounds is like 80 psi at and again, it’s the amount of weight that’s on each wheel. Most people put the same amount of pressure in both tires. But the fact is, you don’t have the same amount of weight on each end. At best, you have probably 6040 distribution of weight, front and rear. So you really ought to adjust the pressure accordingly and have say 82 in the rear and 78 in the front, something like that ran and then you get even performance from both tires.


Chris Case  39:39

This is another reason why people should race cyclocross because we all know that, like we all run different pressures in the front rear tire not not to say that other people don’t get that but it’s just a familiarity thing in a just, you know, second nature that you run a little bit higher in the front inside cross than you do on the rear. Sorry, sorry. Yes, well Why don’t we Why don’t we jump to what you’ve seen in the laboratory, for instance, at this wheel Energy Lab in Finland? Could you take us there and explain, explain the lab explain they, what they do there explain sort of the science behind what they’re trying to prove over there,



the labs called wheel energy, oil. Oil is like Incorporated. In Finnish, they are measuring rolling resistance of tires, by measuring the amount of power it takes to drive a big drum. So you can imagine that the bigger this wheel with a tire on it is rolling on a drum. And obviously, the bigger the diameter of this drum, the more it’s gonna represent what riding on a shared flat road is, like, if you got a small, small drum, then it’s just going to be deflecting really deeply into the tire, it’s not going to be nearly as representative of what you would see on a flat surface. So


Chris Case  41:05

that’s more like riding on a set of rollers in your living room.



Yes, yeah. And you and, and if you’ve done that, you’re sort of aware, like, if you run that at really low pressure, how much resistant Right, exactly, because it’s pushing so deeply into the tire. And then that history’s this curve we’re talking about of that rubber, then returning to its original shape after being so deeply deflected, it’s just a huge energy loss. So they have a giant drum and, and the drum, you can think of it either as as, as have the drum, be free to turn, and you’re driving the wheel, or the way they do it is your that wheel is free to turn but the drum is being driven. And then you set the parameters, we’re going to do test this at 30 miles an hour, say, so you turn the drum at the speed, that the wheel would be rolling down the road at 30 miles an hour, and you measure how much power it takes to drive it. And then you vary the pressure, or vary the tire or whatever it is you’re looking at vary the diameter, the tire the diameter of the wheel, with the tire, lot of variables that tread compound, yeah, whatever it is you’re looking at, and then you you know, you try and compare apples to apples, like you try and try just, if you’re doing tire pressure, you keep the same tire wheel everything and you just keep varying the pressure and measuring how that how that changes, then. So that’s the first thing about it, but the drum the drum is, is it’s a big aluminum surface, so it’s smooth. And that’s not that representative of what you would have on the road. So then, then they have different surfaces that they can then apply to this to this drum to represent different kinds of road surfaces. And so the one that we tend to commonly use when we were doing testing with them was diamond plate, which is you know, you’ve seen it on metal stairs, you know, it’s those metal stairs that have those little pieces of little diamond shaped, raised up section, right, going at different angles to each other. And then and so that’s fairly representative of certainly have a chip sealed road, it’s definitely not as much as much like a gravel road or something. But it’s it’s rougher than, than a really nice road certainly rougher than a than a than a track that really the only thing that’s representative of a good have a good track is probably the smooth roller, but then anyway, they, they have all sorts of different surfaces that they can then wrap around this drum, they also can use it to measure grip, so they can see as the as the thing is turning they can, they can tip the wheel at an angle, and then try and push it and see how much force it takes to make it slip where it releases where it releases. And then you can change again, whatever you want the tread compound, or if it’s there, if the if the surface is wet or dry or tire pressure, whatever and see how it affects that they also do things where they have a piece of the that’s representative of the same type of material. This wheel that’s rolling on the on the drum is then weighted with whatever your the parameter is, you’re gonna say okay, so 150 pound rider is going to have 60 pounds on the front wheel. So then maybe pushing down with 60 pounds or something like that. And then and then you could also do the same thing with this clear surface. And then and then you push down with the same amount and then you take a photo from underneath and you can then actually have you have a picture of this contact patch. You can you can you can measure the the area of it. You can do a lot of things with it. And then especially if you’re if you’re thinking about this grip deal where you then tip it on edge and you and you see what that contact patch looks like on edge and then see, okay, we know that, that this thing slips when the contact patch gets smaller than this


Chris Case  45:19

this amount and then smears into a smaller and smaller shape until it releases. Yeah, yeah, you can find that release point. So last year, you and I, Leonard, we got the crazy idea to do some testing specific to gravel riding since gravel riding is so hot right now everybody’s into it. It’s one of those arenas where you’ve got some people coming over from cyclocross or mountain biking, who maybe get tire pressure in the fact that lower pressures actually going to make a huge difference on gravel bikes, and then you’ve got some roadies coming over. And they’re probably like, now I got to I still have to have 80 psi in my 35 mil tires or 35 c tires, because, you know, because pressure. But we had this crazy idea of not only going into the lab at micro back and testing on their apparatus, but also going out onto a piece of gravel road and doing some rundown tests. I don’t know how many laps I did, we recruited my dad, we recruited some other people, we dealt with wind, we dealt with a lot of other conditions and variables that we were trying to control for. But ultimately, we we learned some things. So maybe you could describe that test. And the payoff at the end of the explanation is we get a sort of a practical answer about what do I do about running? What tire pressure do I run on my gravel bike and then we’ll get into other bikes and other surfaces.






so the one you mentioned was in the lab at micro back in the lab at micro back we tried to represent some sort of situation like you encounter riding on a gravel road and in that case, it was the rider was riding on rollers, and a couple of the rollers had big bars welded on them and and


Chris Case  47:19

reinjure Ridge bump test and it’s just like this thick knob on the on the roller itself so it was an unpleasant ride.



Yep, then you’d have the rider ride at a certain speed so in a given gear at a given cadence on smooth rollers and measure how they have power meter on the bike measuring how much power it took them to do that and then you and then you’d put different rollers with different thicknesses of this of this ridge lengthwise Ridge down the rollers and and the riders getting bounced around you can tell it’s taking more energy cuz you can hear the noise person bouncing around and everything but then measure how much more power it takes for that person to ride the bike at that same cadence and and and the in the same gear and then try different pressures. And and that was one way to do it. Although the while you can measure it very accurately. The question is always well, what exactly does that represent this small diameter roller with a big Ridge on it that it hits every time that comes round? What What kind of a road? Are we simulating and like train tracks?


Chris Case  48:38

I think if you’re riding down to cross a Yeah, trestle bridge, perhaps if you’re doing the Ruta, you’re familiar. I have done that. But otherwise, yeah, it’s not you



don’t know what you’re what you’re what you’re simulating. So how useful is that in the real world. So then we tried to do one that was real world, but rolling resistance is generally a much smaller effect on the rider than is wind resistance. So you want to separate those two. So we were doing it roll down test. So we saw that just you have only the effect of gravity on it, you have the same, the same Hill you’re rolling down same every time and and you’re going from the same point to the same point. And but if you just were to measure the speed measure how much time it took to get from point A to point B. It’s you may not be measuring the tire, the rolling resistance of the tire because you’ll have you’ll have the wind changes in the wind, just all maybe even change the shape changes,


Chris Case  49:47

temperature changes all that



Yeah, you have too many variables. So so in this case, what we did was we had two riders who, who start close to each other but Not so close that there that one of them is drafting the other, we had an electric guy that measures catches them when they start and then catches the spacing between them when they start and then and then catches the spacing between them at the finish and see what the what the time if if one rider is catching up on the other rider is getting further away and by how much and, and then we know on actually on that particular road surface, which is representative of that one gravel road. Sure, then this is gonna be the, the tires that were so we were in that particular case, we did ones where we had a whole bunch of different tires of the exact same construction, but different diameters. And we looked first of all at at different widths at different widths, yeah, sorry, different widths, tire diameter, wheel diameter is still the same on all bikes for the same, what one was faster. And it’s these are small differences in time. So it was important to use an electric guy rather than a hand timer, because it just, there would have been too much error.


Trevor Connor  51:11

So let’s talk some scenarios. So let’s just go with kind of a default starting point, we have a 70 kilogram rider running 2370 958 pounds. Okay, all right. So 158 pounds road race, typical paved surface, running either 23 or 25. c tires for both of those, what sort of pressure would you be recommending to them



on a pretty smooth road, you’re going to, you’re going to probably run 90 on the rear 85 on the front with the 23 millimeter and more like 80 on the rear 75 on the front with the with the 25 millimeter. And then if the person is 200 pounds, then it becomes more like 100 on the rear and 95 on the front and the 23 millimeter and 90 on the rear 85 on the front with the 25 millimeter. Wow. Okay, do


Chris Case  52:13

you hear those gasps out there? I did was lower



than reliable. But yeah, it is.


Trevor Connor  52:21

So what about a crit,


Chris Case  52:22

but this is science



and a crit. If two things going on with a crit that so in on the one hand, lower pressure is going to increase the tire contact patch, you’re going to get better cornering. So a bigger tire sought lower pressure is gonna be good. On the other hand, you get up out of the saddle and you sprint a lot and a crit. And then if you have a squishy tire, you’re losing energy there. You’re doing a balance, I think crit riders in general, I don’t know if it’s just because trackies used such high pressure and people equate, like, Chris with riding on the track or something and, and heart is fast


Chris Case  53:07

Leonard heart. That’s the mentality I



think and I think it is. And there is a feeling like you you get on a bike with really hard tires. And it feels you know, it’s so bouncy, it feels like wow, I just feel fast. You know, you throw the bike back and forth. It’s like immediate reaction. Well, it feels fast and feels bouncy, because you’re doing all the work. Right? The grounds bouncing you along, and every little one of those little bounces is costing you energy that you put into the bike to get it to get it going


Chris Case  53:41

and and fatiguing your muscles in some way over time. Yeah,



I can draw a parallel with brakes. You know, it used to be that, you know, when we all had rim brakes that that people would would get these, these red brake pads are really really hard. You know, because they grab the



grab the pole, they hold that squish.



Yeah, they pull up, pull the brakes and it felt Wow, that’s just really, that’s a heartbreak that’s really good braking, well, it feels that way because you’re doing all the work when a squishy pad means you’ve got this as much greater mechanical advantage and you’re and you’re able to actually compress the pad. That means that there’s quite a bit more force going into the into the rim quite a bit more friction and you actually want a squishy feel to the break indicates higher higher power, not lower power and so better modulation. Exactly. So it’s a similar thing with with the tires, in a crit with sharp turns a lot of sprinting out of the corner you you probably want a fairly hard tire for the exits from the turns and just go with a little bigger tire for better grip so so maybe run 25 and and yeah, that 158 pound guy. Still probably run Maybe 85, rear 80 front, something like that. And then there’s your there’s definitely going to be no deflection on that there’s a hard tire in that diameter when you’re sprinting. But on the other hand, it’s a pretty good sized contact patch, and you’ll be cornering better than that. definitely better than the guys on the 23 millimeter hires at 130 psi even racing.


Trevor Connor  55:23

Right? Who’s still killed me?



Yeah, yeah, yeah, well, and the other thing to think about is that we’re we’re talking about for small differences in pressure and similar ties, tire construction, and all that we’re talking about differences on the order of a water two per per wheel. And when somebody can put out 50 more watts than you, if you’re saving four watts, then you know, he’s still gonna smoke.


Chris Case  55:49

Yes, the thing that I like to remember is Yeah, for for a crit, that little bit of savings is something but if you could, essentially negate it with some of these other factors, just more powerful rider, you take that one corner the right way. And it’s like erases any advantage you had from two watts from the air. But yeah, in dirty Kansa. When you’re racing for 12 hours, yes, and you’re running, you’re running 60 psi in your 4040 c tires. And that is just abusive to your body, you’re just you’re you’re wasting a ton of energy, because of all of these physical factors we’ve described, where as the guy running, or the girl running 30 psi, has a huge advantage, not only in terms of rolling resistance, but in terms of comfort, cornering, grip, it cetera. extrapolate that over 12 hours. It’s massive.


Trevor Connor  56:53

Yep. We’re in a crit. Personally, if it’s really technical crit, I’m willing to say all except a few more watts, in order to be able to get around the corners a little better and not have to worry about slide now, right, exactly time trial, and non technical time to decide about standard out and back, maybe you got a couple turns, that’s about it.



So on a time trial, you of course, have to think about the aerodynamics. First, that’s the most important thing in a time trial. And clearly, the bigger the tire, the more aerodynamic drag, there’s going to be on it. So you also have to have a rim that is made it to that tire size. So you know, airplanes fly big a big airplane, the bigger the airplane, the bigger the thicker the wing is. So it’s clear that you can have pretty low drag of a wing. With a big frontal area, if you have the shape behind it be right, so you can get away with a pretty big tire aerodynamically, if you have a rim that


Chris Case  57:55

matches, it matches it.



But if you if you don’t, if you have this big step, you got a big tire sitting on a skinny rim, then then there’s gonna be all this turbulence there and that’s gonna may be way more difference than the tire ever could. The first thing always at a time trial, think of aerodynamics and then and then assuming that you have a tire that’s matched to the rim, then yeah, 25 millimeter tire, there is a little more weight but in a time trial, it’s um, once you get it up to speed, there actually is no difference. It’s just the initial acceleration and, and you if it’s a straight out, like out and back time trial, there’s only two accelerations at the start and at the turnaround, and so, so otherwise it’s just steady state riding and then you’re just talking about reducing the rolling resistance so you’re going to be better off on you know, most roads have more roughness than you would think. If it seems like it’s a pretty smooth road, you’re still probably going to be faster on a 25 millimeter tire with something like 75 psi in the rear and 70 in the front. You’re not going to lose anything by it. If the rim is is made it to it and if not, you know if you’re got to go 23 millimeter tire in order to have have a rim that matches it better than probably 80 psi in the rear 75 on the front and what I talked about earlier, comfort being a good judge of efficiency, that if you’re rolling along and your elbows are not getting bounced around on the elbow pads because the tires rolling smoothly across the ground, that’s saving you a bunch of energy, you know both in concentration and then your muscles being beaten up by getting bounced around. So if you’re trying to trying to be on a magic carpet, if you can be on you know, just go smooth and have all the little little ripples in the road, just get absorbed in the tire and not get pushed. up into your elbow pads.


Trevor Connor  1:00:02

Now, so we just talked about the three types of standard road racing does rain impact these,



that’s a good question. To get the tire to stick to the road, when you’re cornering, you want to have as much of the tire on the road as you possibly can. And, and so it’s really going to depend on how much rain there is, if the road is just a little bit wet, it’s going to be better to have a bigger broader surface to contact it, if it’s a situation where you have a thick layer of water like you know, where where you’re really shooting up a lot of water up onto your feet and everything in the you’re you’re bracing, pushing a wave along, then what you want to do is cut down through that you want to skinny your tire at higher pressure to get down to actually the ground and not not be hydroplaning not floating up on it. And there’s a similar argument if you’re riding like cyclocross or mountain bike in the mud. Most of the time, you probably be using really, really, really low pressure like cyclocross, you never talked about width because everybody use 33 millimeter width for everything, right? But in most mud conditions, yeah. Okay, you want to have usually, in cyclocross, you don’t talk about tire width, because everybody’s using 33 millimeter with tires. You talk about tire tread, and you talk about pressure in mud. Yes, you want a deep tread that, that digs into the mud and grabs the mud, but also releases it easily has big spaces between it so that the mud can get back out. But in terms of pressure, if it’s really greasy and slippery, yeah, you’re going to be running really low pressure, like, you know, 150 pound guy might be like 14 psi, it’s like ridiculous how low for 33 million tire, basically roadbike.


Chris Case  1:01:59

But they’re gonna run that pressure, if they have lots of wheels, if they only have one set of wheels, they might want to



bump it up a little bit, so they don’t crack him. That’s true. And always and also, it does it is does depend that they might they have to have a tubular tire for the ship your shoe out on a clincher, you’ll just ruin the rims that the rim walls immediately. But yeah, you really run low pressure. But if you’ve got deep mud, you actually the same way we’re talking about hydroplaning, you really want to cut down like you think of pounds per square inch, well, you want to get some of those square inches actually into the ground. And so a tire that cuts down deeper into it is going to be better that you’re going to run higher pressure, if it’s really deep mud, in order to get down and find something to bite into instead of spreading it out over this really mushy stuff on top mountain bikes. A lot of these arguments are the same with mountain bikes that if you mountain bikers, just like they’re using more and more suspension travel every year, they’re tend to get wider and wider tower tires. And also, you know, tire, the wheel diameter.



You know, it’s



fairly clear that people that are racing cross country, where they’re trying to certainly minimize their rolling resistance that that a bigger tire, a bigger diameter tire is going to roll over 29 inch wheel doesn’t fall into a 26 inch hole that you’re gonna, you’re gonna roll over,


Chris Case  1:03:42

you’re effectively smoothing out the ground by that larger diameter just Yes, in the same way, the larger drum doesn’t smash into your tire on a roll set of rollers or the the test that we were describing earlier. It’s the backward the the reverse of that in a way



Yeah. Or if you’re if you’ve got a heavy wheelbarrow load, and you have a really rough area that you’re rolling it over, lot real Rocky, if you have little tiny wheels on that wheel barrel, it’s gonna be really hard to push it compared to one of those ones as a huge, huge wheels. So that’s the first thing is to think about the wheel diameter and then tire width I think people have been you know when the first 29 or tires came out it was 29 by two inch for everybody use and now you know then it went to 2.2 and 2.35 and 2.4 and now it’s 29 plus which is a three inch tire. And that may not be used for cross country racing because of the weight and others. You know that’s the major consideration. People are generally amazed that have been ride and say 2.3 inch tires and they get on three inch and they are amazed at how fast they go. In order to maintain similar hoop stress, you’re going to be running a lower pressure, the bigger the tire, you go to that if you go from a two inch tire to a three inch tire, and say you were running that two inch tire, say at 30 psi, well, now you have to run it at the three inch tire at 20 psi to be at the same, the same hoop stress.


Chris Case  1:05:20

I think that’s an important point, honestly, about all of this is the fact that you might have to experiment a little bit with this stuff to sort of overcome your bias. And also just get comfortable at lower pressures, particularly not none, obviously, you’re not on a road bike, you’re not going to run low pressure so that there’s a different sensation. But effectively, or to be most effective in something like cyclocross or mountain biking and stuff like that, you will run pressures where at times your your your tire will squirm underneath you and it’s a different feeling. So to get the most out of your tires, performance wise, comfort wise, on rougher surfaces, it means running pressures where cornering is going to feel different. Yeah, take some getting used to. But the point being just experiment with this stuff and overcome some of those. Now, that’s not possible to have your tires only pumped up to 75 psi and a 25. c tire and still be fast. Like it’s true. It’s it’s going to be


Trevor Connor  1:06:29

where there’s a huge perceptual component that we all have you think smaller is faster. And you think higher pressures faster. Yeah. Yeah, the science just doesn’t line up with that. But you have to get across, you know, it’s one of these things where it’s just perceptually. If you go with your gut instinct, it’s that that’s what you think. And you have to kind of fight what your guts telling you yet, for


Chris Case  1:06:53

decades, you probably did this, you probably ran those silk tubulars at 130 psi. And they were rock hard, and they felt fast. But it took some time for you to overcome that. And and some people are still fighting that urge to have their tires be rock hard, because it has this sensation of being fast. But all we’re saying is, yes, drop it down a little bit, try it out.



That’s right. And you and if you, you really do like Chris said have to get used to that squirm feel when you start pushing the limits of what of pressure where you really are getting down low enough. For instance, in cyclocross or mountain biking, a lot of times you have your riding on a side Hill, where you need traction on on the side of something. And it should be pretty obvious to you that if you have that tire really pumped up hard, you’re going to slide right off. That’s ideal, right. And if you have, if you haven’t really low, you’re going to be able to the tire will be able to conform to it, and you’ll be able to ride across something where other people have to jump off and run. And that’ll make a huge difference. He, even if the rolling resistance were higher, the fact that you’re riding and they are running, that’s gonna make a big difference. And it’s a very weird feeling at first for sure to be, you know, in my case, 175 pound person riding at 25 psi in a 33 millimeter tire that feels squirmy when you come into a corner heart. And if and when you’re on pavement. Oh, yeah, it feels worse. The Oculus, you’re like, there’s no way this will work it. It’s just like, you feel like you’re trying to turn a tractor. It’s like, what is Yeah,


Chris Case  1:08:30

hard feeling.



You know, because you have so much tire contact patch that you’re just forcing this tire contact patch to twist on the road. Right, right. It feels horrible.


Chris Case  1:08:42

But you were if you were a kid, you’d say you were riding on flat tires. Yeah. Right. Like, but you know. So we’ve already talked about gravel a couple times. We mentioned the the testing that we did, Leonard, we talked about dirty Kansa. And how much you save over such long races and a lot a lot of gravel races, not just dirty Kansa. A lot of gravel races are really long events. So you’re extrapolating the savings out over a huge length of time. But what’s the takeaway there for for gravel racers?



Yeah, I would say the best takeaway is run a lot lower pressure than you think. Then you think you ought to and you mentioned dirty Kansa. I mean, I think one thing about dirty Kansa is that there’s these really sharp pieces of Flint, the Flint Hills of Kansas, and they’re sharp, and you can imagine how much harder the tire hits that if the tire is pumped up hard than if it’s soft. People get a lot of flat tires and dirty Kansa. They cut a lot of tires. And if you can avoid that you’re going to be faster to the less fewer tires you have to change, the faster your time is going to be just impacting those.


Trevor Connor  1:09:59

Those fleets



Sharp Flint things more softly is going to be who view in terms of the durability of the tire as well. Well, Leonard,


Chris Case  1:10:12

we want to put you on the spot. We want to you know, this is years and years of tinkering and thinking and researching this subject. But what are the major? What are the main take homes that people should take from this episode about Zen and the Art of tire pressure.



If you hop on your bike, and it feels really bouncy and fast, tires are probably too hard. That you, you, if you get on the tire and bike and the bike feels squishy and comfortable. That’s probably where you want to be. Just like with your brakes, brakes feel squishy, they’re probably better brakes.


Chris Case  1:10:54

This runs counter to a lot of things that most people have in their in their minds. Yeah, but science bears it out. Trevor, do you have any thoughts here?


Trevor Connor  1:11:06

I’m not sure I have anything to add. I’m actually remembering back a long time ago when I was a cat five. And being really excited because I’d want a cat five race and then check my tire pressure. Because of course when your cat five, check your tire pressure after the race course, of course. And I was at 85 psi. And I was bragging to all my friends. Can you believe that? I won the race. And I was only at 85. And now with what we know that probably helped me. Yes, it probably did. So really all I have to add is there’s many years and just this perceptual thing that makes us think dinners better, higher pressures better. And it’s just not the case, get over the perception get over that years of gut that you have developed. And and listen to what the science is saying.


Chris Case  1:11:57

I guess my final thoughts would have to do with fully appreciating the beautiful tire. I think it’s a neglected and misunderstood part of riding bikes, there’s a lot to be gained there were sometimes we’re talking about sort of small changes in the watt savings, but it it really is a lot more than that we’re talking about this. This sort of fine mixture of grip versus comfort, rolling resistance versus vibration, energy savings versus track, you know, traction, all of these factors go into it. We didn’t even talk about compounds that much we we talked a little bit about the width of rims, and how they made up with with a specific tire when it comes to time trialing. But honestly, rims just continue to grow and it’s changing how people ride and it’s changing what tires they want to ride because they get they can maximize the benefits that you’re getting out of new new constructions or new materials and this sort of thing. So my my take home is really to fully appreciate the often neglected tire.


Chris Case  1:13:24

That was another episode of Fast Talk. As always, we love your feedback. Email us at Fast Talk at Fast Talk Labs.com or call and leave a voicemail at 719800211 to subscribe to Fast Talk on iTunes, Stitcher, Spotify, SoundCloud, Google Play or wherever you prefer to find your favorite podcasts. Be sure to leave us a rating and a review. The thoughts and opinions expressed on fast doc are those of the individual. Follow us on Facebook, Twitter and Instagram. Our handle is at real Fast Talk Labs for Leonard’s in Nick league and Trevor Connor. I’m Chris case. Thanks for listening