Rolling Resistance Testing with John Karrasch
0 commentsMarginal Gains Podcast - Episode 158
Guest: John Karrasch
Hosts: Michael 'Hottie' Hotten and Josh Poertner
Topics:
- Gravel tire CRR testing
- Chung Method testing
- Aero drag vs rolling resistance
- Gravel tire evolution
- 32-inch MTB platforms
- Tire sizing and terrain
- Mud performance and tire clearance
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EPISODE TRANSCRIPT:
Hottie (02:10) - INTRO
It's the Marginal Gains Podcast is brought to you by SILCA, creators of three types of
grease. There's Synergetic Race Grease for bearings, Anti-seize for certain threaded parts,
and the latest Hold Fast carbon paste for bars, stems, and seatposts. If you are building or
rebuilding a bike, treat your parts right with SILCA's suite of highly engineered greases. I'm Michael Hotten "Hottie" on this show.
Marginal Gains is also supported by Shimano. You know, we made some noise on this show about road hookless.
Let's just say Josh is not a fan. The one thing we failed to do, though, is point people to
something that continues to offer a more traditional tire bead interface, something like
Shimano's top-tier wheels.
Shimano, like it has with its front derailleur, continues to stand by hooked rims for a
more secure hold on high-pressure tubeless tires. The C60, the C50, the C46, all carbon race
wheels and all have hooked rims. So if you agree that the hook offers more security, then
give Shimano's road wheels a look at bike.shimano.com.
Rolling resistance is one of the tenets
of this show.
RCR has been a cornerstone topic here on Marginal Gains, but unlike aerodynamics, quantifying
the Watts loss to CRR has been more elusive. People have been chasing it, but the work has
not received the attention it deserves, at least in this show's opinion. In this episode, we
aim to put a spotlight on someone who has taken on the challenge of testing tires and
putting data behind the performance claims.
John Karrasch is our guest. His title, Bike Fitter, doesn't exactly call out what he is now
known best for, but John has become the de-facto expert when it comes to off-road tires and
rolling resistance. John has been field testing mostly knobby tires in an attempt to
determine which tire performance best and in which condition bike fitting pays the bills for
John.
But tire testing makes him a real marginal gainer.
Hottie (50:43)
Okay, marginal gainers like we said in the run-up to the introduction here. John Karrasch
is our guest. John is a pro bike fitter with Cahaba Cycles in Birmingham [ https://www.cahabacycles.com ]. But he's a lot more to this audience. As much as we'd love to direct you to his fitting services, we're also going to direct you to his tire testing.
And it's really not a service, is it, John? This is something you just put out there in the
world. You're tire testing?
John Karrasch:
Yeah, pretty much. Just put it out there. See what people think.
See what questions they have. And, get my own questions go into which keeps everything
going with it.
Hottie:
Well, let's, let's fill the audience in with a little, by the way, Josh
Poertner is here with us two. I don't want to ignore you, Josh, thanks for taking time out of
your busy day. Putting on your SILCA t-shirt here on the stream and jumping in with
us.
Josh is also a CRR guru. So we've got two guys here who've invested a lot of time into rolling
resistance to talk about this topic. But first, John, let's talk a little bit about
your bike backstory and your bike fitting backstory.
John Karrasch:
Yeah. Those, those bells connect pretty far.
So the bike's backstory goes back to 1999 or 2000. Got my first mountain bike, then I was 14 or
15 then and started racing cross-country immediately. And it was huge then. I loved it. So I
quit playing baseball and soccer and just kept going with mountain bike racing and, still
love it.
Still love riding. Don't race as much as I, would like to. Maybe, but that's that's fine
right now. Have done plenty in the past. As far as bike fitting that came in 13 years ago. I
started on the physical therapist assistant, and I started fitting part time just because I
was curious about it, and it kind of fell in line with my work I was doing anyway.
So I started sitting part-time, and then I switched to full-time at the bike shop. Five
years ago. Fitting. So I've still got my therapy license, but I haven't used it in quite a
while, but just, renewed every year, just in case, you know?
Hottie: But that comes into play, right?
Physical therapy and bike fitting. Like, do they really interact don't they?
John Karrasch:
Yeah, yeah. So I started sitting without any kind of, you know, formal, class-based training or whatever, because the way that we, the way that we learn to assess how people walk and go upstairs and do all these different things, it's very applicable to bike fitting.
Definitely enough for if you already knew about bikes and you had us a good outpatient
therapy experience for work, you could probably get going with it and do pretty well. Aside
from, you might not have as much, maybe technical tools yet, but sometimes those aren't the
most important thing with it.
It's mostly, you know, good judgment and listening to who's in front of you.
Hottie: And then, how did the the Chung method first enter your life? Because that's become a big part of it now.
John Karrasch:
Probably from listening to Josh talk about it honestly on the SILCA podcast here and there.
I was thinking about that yesterday. I honestly don't know the first time I heard mention of
it, but I definitely remember hearing there thinking like, that sounds like magic. And I
want to do it. And I don't know. I don't even know when I got it in my head again to try it.
But it was a few years ago, and I had a I had a power meter, and I started understanding
kind of the way it worked. So I took a few shots at it and actually got half decent results,
which now that I've seen other people doing, and seeing their plots, like, I was doing
pretty good at first because it's, it's very easy to produce a really bad Chung test.
Not if not a lot of people realize that, but if they have one that looks like anything at
all is, like, really satisfying. So I was doing that for aerodynamic testing for a little
bit, and then I think I like ran out of stuff to do with it at that time. Like, I'd figured
out my bike is about as fast as I can get it, which we'll talk about that too.
That was three years ago, and it's a gravel bike. So things have changed. But ran ran out of
steam for it then, but, came back to it about a year and a half ago, maybe two years ago now
for tires mainly.
Josh:
And I know it's a good, good point you bring up because we've we've done it
ourselves.
And I know so many people have like, "can I send you my, my file?" Is that like, yeah.
You don't have enough slider bar in Golden Cheetah to get those to, get those to overlap.
John Karrasch:
And so I would, I'm currently reviewing a file from a guy from Unbound 200 this week, and there's definitely some things that are off the charts there.
Looking at it.
Josh:
But it's a great point, though it does seem like so many people like, try it
once or twice. They're like, oh, that's impossible. But I think if you have a good first
experience, you're like, oh, it wasn't that bad. And then you can kind of work your way
through it.
Are you are you using Golden Cheetah or what? What software you use?
John Karrasch:
Not anymore. I use primarily something. It's free on GitHub. Like if you look up Virtual Elevation Analyzer, there's a web app on there now, and there's like a Python code that you can run to terminal on a mac or like through, Anaconda prompt on a windows laptop.
So the basically that, just it integrates all like Robert Chung's original equations into
it. And you can upload a fit file, but it's got a lot more features within it. You can, you
can way more easily select laps. And honestly, everything Golden Cheetah Aero Lab is hard to
do.
So it doesn't take much to easier. But this is way easier. And you can, you can trim start
and end points, which is incredibly helpful for looking at a plot. It's huge. And it's got
it's pretty advanced. It's got overlaid like weather API now for, different places where the
fit file originated from.
And it's even got, kind of geographic, like topographic terrain tiles. Like, if you've seen
those really nice colored maps of terrain near you and it's like, oh, that's got really high
resolution. Those are integrated into it. Also see what's the deal with like weather related
drift or whatever.
Plenty of things to make a GPS drift and it's elevation data. Yeah. So...
Hottie:
Josh, Josh, what are you using right now when you analyze, you know...
Josh:
I honestly, I, I've gotten lazy. I've got two, two guys on staff who. Well, one of them, John F., He's been with me since the Zipp days and he's like a mega ninja at this.
And Travis V. I know you've talked too John and we've done stuff with, he he also does it,
so I, I honestly probably haven't. I used Golden Cheetah, but I probably haven't done it in
five years personally. Okay, okay. So I've gotten very spoiled. I get to like, show up,
drink coffee, look like I'm doing something important, and then other people do all the
actual, like, hard work.
But that's a that is an amazing tool. And, we'll, we'll put a link to that in the, on the
web page for people who want to go check it out and download it, because it's, it really is
remarkable how far, how far the tech is common. Yeah. And continues to progress right from.
John Karrasch:
Yeah. And almost more importantly, it gives people like, an entry way to even get started
with it in the first place. And I think that's really cool.
Hottie:
Well, before we move to tire testing, John. What he was would you say and you too, Josh, are the tenets to gathering good data to get an accurate Chung test?
Josh:
Course, course is key.
You know, we like saddle shaped, courses, right. So you can get a nice speed variation with
power to help. It just helps separate aero from rolling. You know, rider position
consistency is the other one that's.... It takes a good rider. And I think as a rider, you can
train yourself to do it.
And probably the best way to train yourself to do it is to analyze your own data for you.
Like, oh God, I made a mess of this, you know, but, I mean, we've we've done things before
with, with riders. I mean, literally as ridiculous as, like, you know, kind of the old,
like, Italian style, like, fishing line from the, from the jersey to the stem to, like, stop
moving, you know, like, I'm going to strap you to this thing, you know, like, helmets are,
but, like, with aero helmet testing, I'm a big fan of the toothpick.
Know, you stick a toothpick in the back of the tail, and then you tell the rider to stab
them selves in the back with it, like, So they're not, you know, keep them from moving their
head, things like that. Are important. But yeah. And then I think the other one is like so
much of what we've been studying now, and I know you're studying is gravel, and, and gravel
is, is challenging because it's, you know, and like, well, more, much more so than pavement.
It's very line specific. You know, you can ride the same loop, but if you, if you're riding
it with a different line, you're on a different surface. And so I think people I feel like a
lot of the people I talked to who have tried and given up on Chung Method often times have
stories like that.
Oh, you know, I do this gravel loop and I was back and forth like, well, how how consistent
are you in your the line that you're riding because you know, that can that can make for
some pretty big differences. It not to mention it on those rough surfaces. Your body
position moves quite a bit as well.
And so I think that that's another one that gets people really caught up. That's, I would
say probably nine out of ten times when you don't have enough slider bar, to get the two
things even close to each other, like you've got other issues, and that's probably those.
So but at this point I think you're more expert than yeah, than me. So yeah I want to hear
yours.
John Karrasch:
Okay. So yeah. So I the course selection agreed. That's why I got to be one of the
biggest ones from the start. And what I do is it's a saddle course typically. But what I
have done from almost the very start is like a modified version where you would, instead of
a full saddle, you would cut off one side kind of relatively quickly on it, and that would
give you a little bit different offset in like the heights you're comparing to in the
elevation.
So it gives you like it's easier visually to see what's going on with it that way. And it
started for me because one of the sides was just too steep to really be productive. So on
the best gradients I feel like are if you can get, a long hill or longish hill, like maybe,
half a kilometer or something, that's like two, 2% grade, which seems way too shallow to be
of use.
But it's really awesome because you can vary your speed and power, like you said, Josh. And
also it stops you from dumping way down into the bottom of the cassette range and the really
small cogs that can mess up drivetrain efficiency, because that's definitely possible.
And then, you know, you know, rider discipline is also good. And just from fitting
people, I'm pretty tuned in to what my position is like. I've got kind of my tactile cues
for this is how my hands should feel on the hoods right here. And I'll pick like a, an easy
position to stay and not like full aero hoods or whatever for the whole test and kind of
hold your line like, don't be looking around.
Do I try to, you know, focus where you're going. Don't look at the GPS, don't look at your
power. Just ride your course. And for me, having multiple laps that are shorter with really
well-defined turnaround points is really helpful because it's less course total you have to remember the line on and with the line, that's I can see that being really
challenging because the way you might normally ride something might not be how you want to
ride it to do a good Chung test, because you want to keep, especially on gravel. You want to
keep the most amount of similarity between courses.
So you don't want to take one that starts off super buffed out gravel. Then there's a big
rock guard, and then all this. You can do it like that. It's not ideal. It's going to limit
you from figuring out the other kind of CdA and CRR pairs from that. So consistency.
And then, one one thing that I've found is kind of being really careful on like tire
pressure before you start, because once you start riding a bike, the tire pressure you did
in your garage, ten minutes ago might not be what you end up with once you're in your run.
So I'll try to ride for a few minutes, recheck the pressure to see where it kind of
stabilized, and then go ahead and go. And from that point, give it at least a couple of minutes
of letting the tires kind of get to their temperature, because tires get a little bit faster
after a couple of minutes of doing a run.
So you want to kind of get past that period and then finish the test. And, you know, I've
got a kestrel that I can check air density with on the spot when I get done. Also, I get a
good weight of everything, rider or bike, the whole system.
And then also one thing that I've mentioned yet is, tire roll out circumference measurements, like you need a sensor and you need to roll the tire out with the pressure that you're using, to get a measurement for that to, be in your GPS unit.
And that's a pretty important detail. I've done it without that, but it's not good,
and it'll mess up pretty badly. It's almost better to do without a speed sensor than to get
a wrong reading on it.
Hottie: Do you do the roll out with the rider on the bike? Do you want the tire to compress?
John Karrasch:
Yeah. You want to have the tire compressed like kind of the amount that which is honestly just like not the easiest thing to do to keep a bike going totally straight at sort of speed. It is possible, though. And one thing I've done lately is, instead of getting out a tape measure every time, I just marked it out of my garage floor with some hash marks and a measuring tape.
So I just go to the garage, put it on the floor and do my roll out, ride it down the side of
the tire. That's another thing that probably good tip is if you got things you might have to
remember, just go and ride on your tires with a Sharpie while you're doing it.
I will not look into phone notes later on.
Josh:
Yeah, the old silver Sharpie can't. You can't have enough. You cannot own enough of those..
John Karrasch:
I do. I need these, clinics for like, high school kids for their bike fits. And one thing I mentioned during every clinic is, like, for your race bag, you got had a silver Sharpie in it.
There's a lot of reasons, but you're probably not going to regret having that.
Josh:
I love how universal that is. I mean, it's just like every everywhere I've ever worked, every team, every composites shop, every year, like, wow, these. I wonder how many of these they sell
because, yeah, I mean, we go to the wind tunnel and it's like silver Sharpie and there's
like, everybody's got two, right?
Hottie:
So, John, what got you started in the tire testing? I mean, I think you're up to, what,
50? Maybe I counted wrong. Maybe there's not as many on on the database sheet you have, you
have displayed on your website. But I counted 52 tires. What you what got you started in
this?
John Karrasch:
I got started in, because people talked about it a lot. Especially, there was this period
maybe two years ago. Yeah. 2024 people were starting to run more broadly, run
mountain bike tires on gravel bikes. And there was a lot of talk about it as to like why
that might be, whether it was from, my initial thought was that, yeah, you're in a group
going really fast, like you need something preventing you from just smacking all these
bumps with your rim and disrupting the race, when you can't see what you're doing.
And the other part of that for me, which I was kind of wrong about, was I was thinking, oh,
well, these guys have, you know, 370W at their disposal. So, yeah, you can spend a few extra
on having that big tire rolling around. But then there was some more, you'd hear about
they're actually a little bit faster.
And I was like, I was totally in the dark on this because my history for riding gravel has
just been on my mountain bikes, and they were pretty light. They were like, you know, two
nine or single speed, hard tails, rigid fork for gravel, and they would fit whatever.
So I just ran like 2.1s historically. And I didn't have my first for real gravel
bike until probably 2022. So I had very little experience with this kind of conversation,
and I didn't think it was totally out of left field that, like, the mountain bike tires
could potentially be faster in some places.
But I got the thing that pushed me into doing the testing again was I had, I was riding my
hardtail with, Aspen 2.4s on it for everything for the entire fall of 2024. And
that bike was still, it was still pretty fast, even with the aero penalty of the
flat bars or whatever.
There is still a lot of times where I think, like, man, I thought I was going to be going a
lot slower there, but I'm not. So I was like, okay, let's, let's just get into it. And it
started off as, kind of a broader plan anyway because I knew, you know, after the first set
of tires, you weren't just going to say, oh, that's interesting and leave it alone.
So did some work with the, the Aspens. And I started having, you know, pretty good
repeatable results. And I thought, okay, let's, let's do some more. And I was borrowing
tires from other people to use on my bike some gravel tires. And then I got, then this
really, like, got more interesting.
I got a set of when Vittoria came out with their new line of XC mountain bike tires. During
that period, I got some of the Peyotes because, one of my buddies here who's a big guy, he
trashes bikes, and he got a set of Peyotes for a endurance race here, cuz he was like, I
wanted the fastest thing I could to save me some energy out here.
And he made it to the race out, flattening them. And I was like, Holy crap, if Shane didn't
destroy these things. And he went fast, I got to see them. So I got a set of Peyotes and sure
enough, super fast, and that I also had like probably what's like the top of my list during
this period is like the Schwalbe. Thunder Burt 2.1s.
I just kind of. They spoiled the plot and tested the fastest
thing from the very start. But what started to get my attention was like, the Peyotes were a
little bit faster on some of the rougher courses, even on the Thunder Burts, which I
wouldn't necessarily have guessed, but that added this extra layer to it right away, where I
was thinking, okay, now there's definitely like some things to be obtained from this that
are that are way past, like what you would think with, at the most basic level, just look at
a roller drum test and say, oh yeah, this thing's faster.
So let's let's go. And that's the end of the definitely not the end of it. So yeah, started
the Aspens and kept going because I just kept finding more little puzzles or questions along
the way. Really endless, it turns out. And it's my count. Right?
Hottie: Is as, as of this recording, are you up to 52 tires?
John Karrasch:
It's more, it's more, it's more. It's like 56.
Hottie: Okay, okay. And growing.
John Karrasch:
Yeah. That's that's excluding like, that's excluding a few tires. But for, for the most important part of this discussion, yeah, I call it like 55 or something like that.
Josh:
It's, it's, it's awesome to see.
I mean, it's funny, I was just in, LA, what, a week ago? I saw Hottie when I was out there.
But I was doing some talks at some bike shops, and, I was in Santa Barbara, and Tom Anholt
showed up who Tom Anholt was like. Well, Al Morrison was the first guy we ever knew of to do
rolling resistance testing and publish it on the internet.
And then when Al moved and stopped, he handed the mantle over to Tom and then Tom ran that
for years, and I think he quit. So I mean, I'd love that like that. You've now kind of picked
that up and like, you've become the guy.
John Karrasch:
Well, it's funny you mentioned Tom, I talk to him pretty frequently.
He's, he's fairly active on like, the, Escape collective discord. And Tom, Tom's not scared
to ask some tough questions whatsoever.
Josh: And he, he's just retired. So now he's got, like, even more time on his hand because, yeah, he he and I talked somewhat frequently or, or used
to talk really all the time.
And, it was things like, like man, like you have a full-time job and yet you're talking to
like, you know, he's talking to me about stuff probably more frequently than I was thinking
about this stuff, but, but no, I think I think it's just awesome and it's so cool to see it
done, you know?
I mean, those guys were doing rollers and to the it's so much more time consuming to do it,
what you're doing. But I mean that you're able to accrue the number of tests that you've,
you've done is really super impressive.
Hottie:
So for both of you, what are the key differences in the Chung method when doing an aero versus CRR test CdA versus CRR?
John Karrasch:
So okay, I think I'll go first. So with the I have done some of the aero version of it more
recently with, customer fit, customer flight, helmet selection and things like that. The
aero testing, in my opinion, is way easier. So you're, you know, you're going out, find your
cause, getting the pressure in the tires how you want it.
Go ride your loops, switch conditions. Go ride your loops again. And that's, that's outside
of, like, if you're getting into things like kind of textured fabrics and socks that are
more speed specific for their aero impact, that gets a lot tougher. There are ways to do it,
but that is harder.
But for basic like, you know, aero testing, it's it's not super hard. That would Yeah, those
are somewhat simple in my opinion. But then for tires, for tires, there's more. I would say
kind of non-rewarding work at first. Like, just figure out what you're doing.
You got a, you got a first established like I am testing this tire with these clothes on, on
this course at this temperature, and I am repeating it 3 or 4 times, and it's not changing.
That's important because it you can very easily get in a mess of, it's warm.
Or two hours later when you tested the other set of tire, they sat in your car longer and
kind of things will masquerade as, change in rolling resistance that are actually just kind
of setup errors, I would say. And then there's, which Josh is getting to like the gravel
testing has its own, its own share of things that can go wrong with it and demand some
extra, extra bit of being careful with it.
But yeah, that's that's my impression. That's kind of aero versus CRR testing with it.
Josh: Yeah. It's in general, I mean, I guess it depends to some extent, if you're trying to see hidden nipples versus exposed, that that's really hard. But like, you know, a lot of these like
positional things or helmet A versus helmet B, the differences are oftentimes they're just
big.
Right. And and I think that makes it a little bit easier to, to see some of that stuff or to
find it. Yeah. In the Chung method and the other thing. Yeah. Back to the gravel testing.
You know, like, I mean, back in the day when we were creating like, all of the rolling
resistance data that you see, like at the SILCA website, you know, that was all done on
road.
And so you're able to do it in like, like with the rider or in aero bars, skin suit, aero
helmet. Like you really try to minimize the aero and you the rider can keep real consistent.
Right. And then you take that to gravel and, and it's a lot harder for the riders to stay is
consistently positioned.
I would say compared to, you know, you lock somebody into aero bars or like, I said, you tie
them with a string to their stem. And.
Hottie:
All right, John, since you've been through some almost 60 tires now, I guess, what what are the big takeaways with all of this CRR testing you've been doing in the field?
John Karrasch:
I've got a few. So one thing is, how how good tires have gotten, over the last few years.
For a while. For many years, actually, gravel tires were just kind of like, redone touring
tires with some different tread on them. And, I'm not going to say they were, like,
carelessly designed or anything, but the a lot of the tires that are out now have way more
effort, put into them even tires that were decent before and people would not complain about
them unnecessarily very much, but they're way better now.
The other thing would be, how, just the effort made by manufacturers to, like, improve
gravel bikes, wheels and tires. The speed at which that's changed the last three years is
pretty impressive, especially considering it's such, it's such like a back and forth market
with gravel.
Tech and gear. There's a lot of, like, maybe competing ideas on what should be what might be
the fastest or what might be best. But now there, there's, people have way better shot at
making a gravel bike now for themselves. That's, faster, safer, and probably ultimately,
like, a lot more fun than, than something from 5 or 6 years ago, I would say,
Josh: hey, I love it.
I think we talked about Tom and Al earlier. I mean, I think between Al, Tom, Jarno, at
bicycle rolling resistance, and yourself, I mean, you guys for non-industry privateers will
call them. Really forced this huge change in the industry. I mean, it was six, five, six
years ago talking with tire companies.
And a lot of them didn't even own rolling resistance testing equipment I mean literally like
like they weren't even testing for it. And, and that's really had, that's really had to
change. I mean, I mean, to the point that it's, it's funny, I know, Jarno said he won't
test, he won't test prototypes anymore because he's convinced the manufacturers just just
use it so they can pick the fastest one to win in his test.
Like, of course, Jarno, of course that's the point. Like, but it is amazing that that I
mean because you nailed it I mean I and I've ranted and it's I love to rant on this topic.
I mean, like the original gravel tires were just garbage right there. You know, you're being
super nice about it.
But I mean, they were they're like, hey, let's make a big road tires and then make them like
four times thicker and and then cut some tread and so that it kind of looks more like a off
road automotive tire. And, you know, they just made these pigs that were heavy and slow and
well,
John Karrasch:
I'd probably I'd be less polite about it if I'd ridden more of them myself.
Because like I said earlier, I'm not that kind of era of tires. And I was riding like pretty
good. 29 by 2.0 is like 12 years ago for gravel. So but I saw what people were going
through, fixing flats and busting the rims. And even when you had the thing optimized like
it did, not very good either.
So it it's a whole new world for sure. Now.
Hottie:
Are the gravel tires starting to close the gap dry? I mean, I think the given was and I think you found this out through your testing that, oh, wow, mountain bike tires actually perform better. Rolling resistance wise than gravel tires to general statement. Have, have the gravel tires have they started to close the gap there?
John Karrasch:
Yeah I'd say so. That's not across all manufacturers. And there's also plenty of these I've
not tested. So I imagine there's a lot of tires out there. They're just god awful slow still
and like not very durable. But I think Schwalbe was probably one of the first to really,
like crack this with, with with kind of the idea, like, let's take the best of what we've
learned from our mountain bike tires and from our road tire lineup and make a better gravel
tire with their new Pro lineup they have. And they really did that.
And that's, that's also another example would be like Maxxis with their, with their new hyper X lineup. Maxxis had Maxxis is going to sell plenty
of tires no matter what, but they went to the effort of vastly redesigning, like the
compound and the actual construction of those new hyper X tires to where they are.
They're pretty decently fast and they're durable. I think they got a pretty good, product
there.
It's, it's, I think, pretty impressive. What they put into that. And they even did, I
got a set of the. I guess we'll get the the soon of their 32 Aspen ST's, which is a
mountain bike tire and brand new and uses the compound in new hyper X compound from the gravel
lineup.
So you got some kind of borrowing back and forth now going on, which is probably the way it
should be. I think.
Josh:
Yeah, 100%. Yeah. I mean, I think that the industry just came at it from
the wrong side. I think everybody initially said, oh, these are like road tires, but beefier
and bigger and bigger.
And what we really ended up needing were mountain bike tires lighter and smaller, in a lot
of, in a lot of senses. And, and I think, you know, a catalyst for that. I mean, we'll take
some credit. You know, that wind tunnel test we did with Dylan, Johnson where, you know, you
had tested the, was it the Conti Race King or whatever It's called?
The the 2.2. And then we wind tunnel tested it. It was. No, it was actually
slightly faster than some of the gravel tires out there. And and I mean, that when that came
out, like, hey, this tires, you know, whatever. Six watts faster rolling and two watts
faster aerodynamically than some of these gravel tires.
It's like it just went crazy, you know, and they, I mean, I think of the. Was it the bike or
bicycle station guys, they've they're doing some of their own testing and I know they yeah,
they did that Thunder Burt and you did the Thunder Burt and that went out. And you know,
they're like, oh my God.
It's the number one selling tire and gravel now. By by a lot. Right. Because because you
guys called it out as being fast. And so it, yeah, I, I'm super excited for that. For the,
the change that you all have have really brought to the industry.
John Karrasch:
Yeah. If people pay attention all that too, I can, I can see I can see how those tires are selling, from our distributors at the shop.
And I remember when somebody told me those new continental 2.0 Dubnitals were coming out kind
of round, Sea Otter time. And I, I was to some 9 a.m. the first day they came out because
I was thinking, these are going to sell out like crazy. And they sure enough did.
Those are real hard to yeah right now. And they're good. Yeah, yeah.
Josh: Maxxis is a good one too. I talked to them a few years back. I mean, they were they were not conducting rolling resistance testing in their development process for tires. And now they wow. And now they are.
John Karrasch:
Yeah, that's a cool change to see.
Josh:
Yeah. So I think that's that's awesome. Right. Well, one
of the things I love about this sport in this, in this industry, right, is that people
really you can directly correlate some changes like that. You know, it's you know, Toyota
doesn't care what you think, right?
Right. They're not going to change what they're doing.
John Karrasch:
Well, that was that was kind of that was that was something I was thinking about from the start of doing this. So I was like, yeah, I know my friends care and other people care some. But how much are manufacturers going to care or dislike this?
Or, that was totally unknown to me, but that part's been good, too.
Hottie: It has? Well, it's one
of the things I wanted to ask you. Is there been any blowback from any manufacturer who saw
your testing result and said, no, no, you've got that wrong or we dispute that, or is there
been anything wrong?
And we know that Adam Kerin down to Zero Friction Cycling puts up with that all the time. He
gets in little battles with lube manufacturers. Have you seen the same from tire
manufacturers?
John Karrasch:
No, not really. I've had tires. I've tested that. I, I try, I try to stick
pretty hard to like kind of the numbers, but no, no, no pushback from anyone.
And that's probably, partly from just kind of being careful with what I test, like, I don't
I'm not out to like, test. I retire on the market or anything like that for sure.
Hottie:
So, John, you know, what a lot of folks will try and do is read a hot patch and try to make
conclusions about how fast the tire is.
They'll say, oh, this one has higher TPI. It's got 120 or 240 or what have you. Oh, this one
has a firmer tread compound and try to say, oh, that must mean it's a faster tire. So tell
us about what you've discovered regarding hot patch information and real world testing.
John Karrasch:
You can't trust what's label on a tire to know how fast it's going to be, that's for sure.
And you hit on something there with the, kind of the harder tread compound and, tread
compounds that are hard. Like, if you push your thumbnail onto them, how much they deform,
that doesn't necessarily, like, matter a ton for this.
If you take if you took, like, the ten fastest tires I've tested and tested the durameter or
the hardness of them, it's probably gonna vary some. So that's none of it's like a direct
lead in to, to what's going to be fastest. And even like one thing you hear a lot is like,
oh, this tire so subtle, just like feel it.
How fill a fast. It's going to be. And I got a big old shelf of tires here and they're all
fast. And if I'd sent somebody over there to like, squeeze the sidewalls and tell me which
was fastest, I guarantee they would not be able to take the fastest tire in that pile
because that that thickness varies some.
The actual like probably the chemical formulation of the compounds, one of the biggest
things I would say, which is invisible to us, so you can't, you can't pick, like, based on
what that says on the side, because a lot of them will say the a lot of them just say the
same thing, you know, it's like, yeah, it's fast rolling center tread, whatever, percent
faster than the old one.
And the TPI thing that, that, that one really sticks around that is held, as truth to a lot
of people. What's going to be fast or slow is I can say like, that that is not the not the
case there.
Josh:
Yeah. It's a it's a great point. And I mean, we talk about on this podcast all
the time how like our industry has been so good at assigning benefits to features that it's
just the conventional wisdom you know, like, oh, this TPI is the fastest.
Oh yeah. Clearly these tires, you know, I mean there's, you know. Yeah. Like you said, I
mean,
John Karrasch:
well and people kind of people kind of run with these storylines once they're out
there too. It's like you hear it and it's like whatever sounds good to me. And that's that.
Until somebody like says otherwise about it.
Josh:
But I think the manufacturers keep also play into it. It's easy right? I mean, I totally see the, the allure, right of like, oh, if you know, everybody thinks this feature is makes it faster. So let's talk about that.
We also have that feature or this.
John Karrasch:
Yeah. Like I was saying, all of them say the same thing
Hottie:
And then tire size too. I think we try to make conclusions about tire size and speed. Is
there is there a fastest size, especially in the off-road world?
John Karrasch:
No. And that's because off-road riding varies so much.
As far as like, how rough gravel is or even how soft the surfaces, and both of those are
what play into like how big a tire you might want. So if you got really buffed out gravel,
that's super fast, is, you know, who knows, maybe a 35 GP 5000 is fastest. And likewise, you
know, once it's starting to get rougher, most people know when it's getting rougher.
They need a bigger tire. But when it gets softer, you also need a bigger tire. And that's
the thing people miss a lot. That's that's the deceptive part about benefits of, like, more
tire volume is like less kind of surface displacement. And you can for, from my estimation,
a lot of gravel roads are kind of around like medium or category two level and from, from
testing over the last few years, like comparable tire models between sizes.
There seems to be benefit definitely getting up to like 50 or 55mm, but not
necessarily past that. So running 2.4s across all gravel would be probably a
questionable choice unless you just really knew you, needed them to handle the technicality
of it.
So it's it's it's certainly beyond like, oh, mountain like tires fastest. Not not quite.
Josh:
Yeah. That's a great point. I mean, we've certainly seen in a lot of our data the, the, the
really big sizes. You are really only helping you when you need the buoyancy. Like, you
know, like like like you said, soft surfaces.
Right. Or sand, you know, what is it. What's I love that that sand higher that Schwalbe
makes. It's like 2.5 or whatever it's like for sand. That thing's crazy. So they've actually
got a they've actually got an actual gravel tire. That's a variant of that. Now it just came
out.
It's a 60 millimeter G-1, RS Pro and it is huge. It's 60mm wide. It's got some it's got some
flavors of like the giant beach tire with its construction and it's, Well, this is your
first taste of anybody. It's not on a Patreon. That tire is, like, super fast. It's probably
the fastest of all the the RS line, rolling resistance wise on pavement, which is pretty
crazy.
Josh:
No. That's awesome. Yeah, that beach tires like paper thin and crazy fast and so but yeah,
John Karrasch:
it is. I wrote I wrote it everywhere too. I never I never destroyed them. Somehow it's a fun
it's a fun ride. I, I think so it's super fun.
Hottie: Where do we stand with mud? I mean, pretty
hard to test CRR for mud, but we just saw an unbound. Another one where mud became a huge factor.
Is there any way to advise athletes on what to
do if they're expecting muddy conditions or conditions where they're going to have a lot of
collection of mud on their tires?
John Karrasch:
I would say, yeah, you better. You gotta be careful that bike out there, you want to have my opinion, you want to have a solid eight millimeters of
clearance from tire frame and probably 10 or 12 if you can get it. I've got a buddy who ran
an Allied Able up there this weekend, and he did well.
And he ran a 55 front tire, but a 45 rear on that bike that takes like 57. So he had a good
margin to get through. And he did not get really stuck badly anywhere. But it's, it's quite
tempting to get greedy with running a bigger tire when there might be rain, and kind of
hoping for the best.
But the, the downside of that is just it's huge and it's slow. You know, if your tires are
scrubbing, mud everywhere, you're not rolling very fast. Or if you're wasting time on a side
of the road, like, digging mud out of your frame. That's not good either.
Josh:
Yeah. Unbound is always so hard to. I mean, really, I think exposes just like, how different,
different MUDs are, right? You know, like, you know, like, I mean down, you know, you got
to, you know, Georgia racing and I mean you guys have some have added in Alabama to that red
clay mud.
Right. Which is, is, is just totally unique. You know, you go to the northeast and use life
like, like soupy, sloppy, slimy mud, right?
John Karrasch:
Which yeah, we have a lot of that too here. We have a lot of we have a lot of mud where you can or wetness on soil, or you can still run
like bigger tires.
It's going to like, trash your bearings and things. But you will. You saw some of this in
South Korea at that recent World Cup. With the really sticky mud, that I've come across out
in Tennessee here at all the dirt, dirt, sweat and gears 12 hours. There was also, unlike
fresh cut trails, that got super muddy.
So you can do it. It doesn't happen really often.. That's a horrible situation when it
does
Josh:
You hear that bike manufacturer's? More clearance. but, Yeah.
Hottie:
All right, Josh up. Put your
fingers in your ears or turn down your headphones. I as I ask about 32s because I know
this has become, why do we keep talking about 40 inch.
Josh:
I think because it's it's 40in the future. There's. Why why are we talking about the past?
Hottie:
Hey, look, I rode 32s John. I had fun on it. I couldn't tell you if it was faster or
not. I certainly didn't have the wheel size in its in its real. I think, area where it can
shine.
I had it on single track. We're going up and down, we're doing some twisty-turny stuff, but
I had a good time on the on the wheel size. You've had it into the Chung method, had a look
at it. Can you make any type of claim, any type of put any kind of number behind what,
32 can or cannot do as far as performance?
John Karrasch:
it can most certainly roll faster from what I've
seen with the aspens in the best example, because they're the most widespread model, and the
29 and 32 versions are very similar.
Both those I had a brand new, I'd say like from even from even on pavement and smooth
gravel, the there's a significant gain in like, rolling resistance, wattage. Probably like,
I'd say on pavement, it's like seven watts, I think for a pair of tires at 30 Km and then off
road, it's like probably more like 9 or 10 at 30 Km across until you get to, like, rougher,
like I've got a single track course I can do Chung testing on.
It's really rough and it's like, I'll pair it down that one. I'll say it like 12 miles an
hour. It's still like on the single track. It's like a 12 watt advantage for the 32s.
So there is some there is some real benefit there. Of course, you know, they are, they are
heavier and but that, that starts getting back in the old discussions people had when 20
Niners came around.
So there's a lot of, there's a lot of this like discussion that I'm like checked out on
because there's the whole reason I built this bike is because there are so many people chit
chatting about these 32s online that hadn't ridden, and then much fuel that also had
ridden them or seen them responding to it.
And there's a lot of back and forth there that wasn't real productive. So I've got one. I
like it, rides fairly normal for me everywhere at 5 ft - 9in. It's, it's I'm in the
southeast. We got a lot of tight singletrack here. That's probably one of the biggest
surprises for me is I put this the very first ride.
I put it through some of our, like, tighter, like, kind of cross-country race course here at
Oak Mountain. And that bike is real, real fast. And that's even with a chainstay length with
extra chain link on the sliding dropouts that I could take out. And I haven't even bothered
to take it out because I haven't found any real disadvantage to it being kind of a long bike
so far.
So the bike so far has like the obvious things you'd think of, like roll over. But there's
some, there's some seems like there's some handling and cornering benefits there that are a
bit beyond what people... they're a bit opposite what people might think, like the first thing is like, oh, it's not this won't be nimble or is going to handle like a boat.
And it's like I'd say it maybe riding style plays into this. I've ridden for a long time.
I'm not new to it, my best advice. Just like any other bike, if somebody think most
people will be able to ride one of these at some point, I'd say go ride one and see what you
think about it.
You know, if you think it's awesome, like try to get one if you don't like, 2.9er is good or whatever else you like riding, like there's, it's totally okay for people to,
like, ride bikes that they like riding.
Hottie:
Agreed.
John Karrasch:
You know? Yeah. That's the comment I, I ran into a lot of.
Hottie:
Well, the question I heard a lot at Sea Otter was, well, what's what's the problem that the
32 was a solution for? And I said, well, maybe it's not a solution. Maybe it's just fun.
Yeah, maybe that's all we've got here. That's my thing is just something different to try.
And, it's been it's been good for me. It's, And it's going to depend on your use case, too,
you know, like, I've got, I've got a new 29 inch gravel bike that'll be here soon, and I, I
could have gone way out of my way and made it a 32, but right now, that bike's going to be
pretty fast.
And I'm not. I don't think with parts that are out right now, I could have gotten it quite
as fast with 32 parts that that might. I'm not so sure about. I think that a Scott 32 is
that unbounded. Probably pretty fast. I don't mean numbers there, but I yeah, I like those.
Josh:
Yeah, those are, those are pretty sweet. I'm not gonna not going to lie though. There we're
John Karrasch:
I can't believe I can't believe they were there. They are still like that just blows my mind. That
they did that much work to get them that, like, polished looking for that. It's incredible really.
Josh: Yeah. Yeah. No that that was, it was pretty sweet. And they bagged a win in the 350.
So you know cam had a bad day.
John Karrasch:
yeah. And there's something I want to hit on real quick
there. Like there's there's obviously some discussion around like oh is this new bike like
good or bad because it won this race or didn't win this race.
And that's just that's just not the way to look at it, in my opinion. Let riders win races
ultimately, no matter what. Bike is there to some degree. So it's for something new though.
Just the fact that it, like, made it through that, relatively well, I think is remarkable.
Same can be said for like the new crux five or whatever. It's a hard race to get through in
any bike. That or rider and teams that get through it like that's a that's a solid job right
there.
Josh:
Yeah. I'm happy to see too, that it really seems like, you know, in 29ers came out a
lot of the complaints for were real, right.
Like the bikes got long. I mean the the geometry just was not figured out. And so it was
like, oh, this wheel rolls faster. But then I think for at least that first couple of years,
maybe 1 or 2 iterations of frame, it's like it just didn't seem like anybody was really
taking advantage.
John Karrasch:
There were some terrible bikes.
Josh:
Yeah, because the bikes kind of sucked and. Yeah. And and
the industry, I'll say is definitely seems to have like gotten this one much, much better
because I mean, you, you said it and, and I think everybody well almost everybody I know
who's, who's ridden one or been on one has been like, yeah, no it rode great.
And yeah, for those of us who lived through the early 29 or days, that was that was not.
Yeah, that was not the case.
John Karrasch:
Well, one thing that was going on there a lot was, an effort
to, like, weasel around with the geometry to like, make it handle like a 26, which didn't
handle that great to begin with.
So it's, hopefully, hopefully there's a little bit of like, appreciation for, like, let's
just make this new bike with some geometry we think is good and see how it rides and go from
there, as opposed to trying to make it something that's not maybe, you know,
Josh: that'll that'll
go a long way, I think, in helping helping with some of the adoption.
Awesome. Well, John, thank you so much for being on with us. We will link your, your site
and your content, on our website so people can see it, and find you. And if, if they want to
just Google search it, what what should they Google search to find you?
John Karrasch:
if they just search
for, mountain bike and gravel tire testing, along with my name, John Karrasch.
They're going to find it. It. Yeah, it pops up pretty quick everywhere. Partly is benefit
from having a strange last name. I've realized. So Instagram is like flex fit by John. That
one. That one's probably like first stop. I would say that. Yeah, I guess like some early
stuff in the stories or whatnot, but it's pretty easy to, keep up with it.
Josh:
Awesome. Well, huge thanks for being with us today and, really enjoyed it and we hope to
have you back soon.
John Karrasch:
Absolutely. That was great.
Hottie:
Thanks again to John Karrasch. For that Google search, John's last name is spelled K-A-R-R-A-S-C-H.
On his webpage, you will find his testing results that include raw CRR numbers for each model and a watts saved estimate for each model.
And if you like what John is doing and want to see more, you can support him on his
Patreon page.
You can support this show by simply recommending it to your fellow cyclists.
By the way, there's a new way to find us, and that is by going to SILCA.cc and clicking
on the big "MG" tab at the top of the home page.
That tab not only takes you to the show, but all the blog posts and videos being produced by the team. So, we will be back soon with another episode. That's it for now. Thanks for
listening to Marginal Gains.