Tire Test Results

Tire Test Results

Last week, we talked about how real-road tire tests have revolutionized our understanding of how bicycles work. We’ve looked at different ways of testing tires, and why it’s so important to perform tests carefully and under realistic conditions. Today, let’s look at some results of our testing.

Are Wider Tires Slower? Or Faster?

The answer is simple: ‘Neither.’ Above is one of many tests where we compared tires with the same casings (Rene Herse Extralights) in different widths – the numbers show the time it took to roll through the timed section of our 132 m-long test hill. (We did multiple runs for each tire to get more precision; above are the averages.) The tiny differences between 28, 32, 35 and 44 mm-wide tires are not statistically significant – they are the inevitable ‘noise’ that you get with all tests. We tested at low speeds (15 km/h; 9 mph) to isolate rolling resistance and minimize the effect of aerodynamics on our results.

What about the wind resistance of wider tires? Above is data from higher speeds (29 km/h; 18 mph) that confirm: Even at speeds where aerodynamics become an important factor, 44 mm-wide tires are no slower than 28s. (Above shows a typical test run: We ran the wide tires four times, then the narrow tires five times, then the wide tires twice, to make sure that conditions hadn’t changed.)

Why aren’t wider tires less aero? Even a 44 mm-wide tires doesn’t have a large frontal area, and on modern bikes, the down tube is wider than that. When did somebody suggest that a wider down tube slows your bike down significantly? This isn’t to say that with certain wheel configurations and perhaps in crosswinds, wide tires couldn’t be very slightly less (or more) aero than narrow tires, but at least for the tire widths we run on all-road bikes, there’s no real benefit from going to narrower tires to gain speed. Other factors are much more important (see below).

These tests were performed on smooth pavement – the most favorable surface for narrow tires. If narrow tires aren’t faster on smooth pavement, they won’t be faster anywhere (except perhaps on a wooden track surface).

This still goes against what many cyclists believe – or even feel, because there is a tendency to equate vibration with speed, and narrow tires vibrate at higher frequencies. (We call this the ‘placebo effect’ of narrow tires.) And yet we can consider this settled – it’s been shown so many times, in so many tests, with different methods. (But your riding buddies may still tell you that you’d be faster on narrower tires.)

What about rough roads? That’s where the suspension losses become even more important, and wider tires are definitely faster. In conclusion: On smooth roads, wide tires are as fast as narrow ones. On rough roads, they are faster.

Tire Pressure

The question of optimum tire pressure is both simple and complex. The simple part: With supple tires, pressure doesn’t make a big difference. Above are the rolldown times for Rene Herse 700C x 42 mm Hurricane Ridge Extralight knobbies on smooth pavement. Whether you ride them as high as 40 psi or as low as 30 makes no real difference. At 20 psi, the tires become quite wobbly, so you don’t want to ride them that low – and yet you could without losing much speed. At 10 psi, the tires are almost unrideable – and finally a lot slower, too. In other words, the tires get too soft to ride before they become much slower. That’s the simple part.

The complex part is that there are small differences, and they are statistically significant: The ‘middle’ pressure of 35 psi – what I’d have chosen in the past as a ‘good compromise’ – is actually a little slower than either high (40 psi) or low (30 psi) pressures. We’ve found this with other tires as well, so it’s not just a fluke with these tires or some testing error. The effect is small – if we plug it into the calculations of realistic road speeds, we’re looking at a difference of about 0.15 km/h (0.1 mph) at most. Of course, what ‘middle pressure’ means depends on the tire and the rider’s weight. (For a 25 mm racing tire, the slower ‘middle pressure’ is around 100 psi.)

The mechanism behind this appears to be this: As the tires are pumped up harder, suspension losses (caused by vibrations, brown) increase more than the hysteretic losses (caused by deformation of the tire, blue) go down. As a result, the total combined resistance (green line) goes up at first. So you can either minimize suspension losses (low pressure) or hysteretic losses (high pressure), but the ‘compromise’ means that both suspension and hysteretic losses are relatively high, and you go slower than you would at either end of the spectrum.

What does this mean in practice? This testing was done on a very smooth road – on a rougher road surface, higher pressures are always going to be slower. (We tested that, too.) Unless you ride on very smooth roads all the time, low pressures are going to be faster, until you reach the point where the tire becomes wobbly and really slows down. There are two caveats: 1. Always keep your pressure high enough that your tire doesn’t collapse under hard cornering or braking (a clear sign that you are getting into the too-low/slow pressure range). 2. Low pressure puts more stress on the casing: The sidewalls of your tires may wear out before the tread rubber gets thin. (You’ll notice that your tires become more porous and not seal up tubeless any longer.)

Casings

Our testing confirmed what professional racers have known for decades: A supple casing is the most important component to make a tire comfortable and fast. This is much more important than the small differences we’ve seen above with tire pressure. It’s more important than almost any other change you can make on your bike. (Let’s assume you’re already riding a performance bike with a relatively inclined position and wear close-fitting clothing.)

Above are our four casings (Extralight, Standard, Endurance, Endurance Plus) and three tires from other brands with the fastest casings that these makers offer. All tires have smooth treads and measure between 44 and 48 mm actual width. (Except the FMB cotton clincher, which is not available that wide.) Small gaps between the bars mean that the differences are not statistically significant. Large gaps mean they’re significantly different.

The Rene Herse Extralight rolls fastest, closely followed by the FMB cotton clincher. The Schwalbe G-One, Rene Herse Standard and Rene Herse Endurance all roll at the same speed. The Rene Herse Endurance Plus is a bit slower – the difference to the Standard/Endurance casing is roughly the same as from Standard/Endurance to Extralight. The WTB may seem like a lone backmarker, but its performance is actually quite respectable for a tire that is mostly intended as an OEM tire (and thus has to meet an extremely competitive price point). (We bought ours at a local shop, but they seem to be the same as the OEM version.)

Before we continue, I want to say that I’m not entirely comfortable sharing our data that shows our tires being fastest. We performed these tests to assess the performance of our Rene Herse tires, not for marketing purposes. I’d prefer to see independent testing, but we don’t know of anybody doing real-road testing of tires.

In the end, the goal of our tests is not to persuade skeptics, it’s to develop better tires. And those who’ve ridden all these tires won’t be surprised by the test results – you can feel the differences on the road.

Different Tires

This is the graph everybody wants to see – showing the performance of the actual tires you can buy. We also included latex tubes from FMB, tubeless setup, and a knobby OEM gravel tire. (Unless specified, the tires were run with lightweight butyl tubes.)

Latex tubes make a big difference. At least when combined with a supple casing, they provide an advantage that’s similar to going from the Rene Herse Standard to the Extralight casing. We also ran our Endurance casing tubeless – we actually used the same tires, taking out the tubes and mounting them tubeless between test runs. Tubeless or with a butyl tube makes no difference in speed. Removing the thin rubber membrane of the tube should make the tire faster, but adding liquid sealant increases resistance and slows it down. (If we make the tire airtight without sealant, we need to add a rubber membrane to the casing, which also makes it slower – we tested prototypes of our tires with the rubber membrane, but decided not to put them in production.)

This settles the tubes vs tubeless question: If you want to go fast, use latex tubes. Choose tubeless because it’s less prone to pinch flats, not for speed. Run butyl tubes if you prefer easy setup and don’t want to top up sealant frequently.

The figure above shows the actual sizes of the tires in this test. As we’ve seen earlier, how wide a tire is doesn’t affect its rolling resistance. 28, 32, 35, 38 and 44 mm tires all perform the same if they use the same casing and tread pattern. We’ve tested this for our Rene Herse tires, but it’s probably true for other tires, too.

All the tests above were done at low speeds to tease out differences in rolling resistance. At low speeds, we don’t have to worry about very small variations in rider position that affect the aerodynamics. The low speed is the reason why the test bike is a whopping 45% slower with the slowest tire than with the fastest. Of course, few of us ride at 8 mph (13 km/h)… What we really want to know is what all this means at more realistic speeds.

Flat Road, 150 Watt

To put these results in context, we calculated the speeds for each tire with a power output of 150 watts. We used the drag coefficient and frontal area from Bicycle Quarterly’s wind tunnel tests, the tester’s weight, etc., and plugged all those known factors into www.analyticcycling.com. Each rider’s speed will vary a bit depending on these variables, but the difference between the tires will be similar.

Now we can see what this means in the real world… If we switch from the Rene Herse Standard casing to the Extralight, we’ll go 0.3 km/h (0.2 mph) faster with the same effort. Going to the Endurance Plus casing, we give up about the same amount (0.4 km/h; 0.3 mph). The difference between the fastest and the slowest smooth tires is 1.3 km/h (0.8 mph) – or about 5% of the bike’s speed. (The light-colored shaded area for the Raddler knobby indicates that we don’t really know how this tread profile behaves at higher speeds – unlike smooth tires, knobbies have complex dynamics as the knobs flex differently at different speeds.)

This shows that choosing your tires makes a significant difference – a set of aero wheels makes you only about 1-2% faster, but choosing the right tire easily can make a difference of 5% or more. You’ll have to pedal a lot harder if you’re on the slower tires in this test and want to keep up with someone on really fast tires. For this round, we only tested tires that are relatively supple – in our previous tests, we included stiffer tires and found even bigger differences.

Flat Road, 400 Watt

Let’s assume our rider is a really strong racer and puts out 400 watt – which means they ride at about 25 mph (40 km/h). As a percentage of speed, the differences get smaller at higher speeds – aerodynamics make up a larger portion of the resistance. In absolute terms, the speed differences remain almost constant: Going from the Standard to the Extralight casing still makes our rider roughly 0.3 km/h (0.2 mph) faster, and you give up a similar amount going to the Endurance Plus casing. And the difference from the slowest to the fastest tire is still about 1 km/h (0.6 mph). In a strong group of well-matched riders, these differences are hard to overcome with leg power alone. And remember that when you’re drafting, wind resistance is much smaller, and tires play an even bigger role.

Now you know why pro racers all ride on supple casings – on slow tires, they’d have to be a lot stronger than the others just to keep up!

What about Rene Herse Knobbies?

We designed our dual-purpose knobbies to roll (almost) as well as our smooth tires. Many riders report setting personal bests on our knobbies – on pavement. Above is a comparison of our knobby Steilacoom and our smooth Barlow Pass, both in the 700C x 38 size and with Endurance casings, at a speed of roughly 29 km/h (19 mph; individual runs shown). There’s no measurable difference between the knobbies and their smooth-treaded equivalents. The averages are identical, and the variability between the nine runs is just 0.31 seconds. If there’s a difference between these tires at moderate and high speeds, it’s extremely small – too small to matter even for competitive cyclists.

There are a number of reasons for this. The biggest is that the knobs of the Rene Herse tires are so big that they don’t squirm signficantly. There’s a lot more to the performance of knobby tires than we can cover in this journal entry. At low speeds, the knobbies are a little slower, because the knob edges deform – at least when they are new. As the knobs round off with wear, they get faster at lower speeds, too. If you’re interested in the full story, check out the Spring 2021 Bicycle Quarterly.

Summary

All this data is interesting, but let’s not forget why we test tires and obsess over supple casings: Great tires make riding so much more fun. They make adventures possible that used to be just the stuff of dreams. Which tires you choose is mostly based on personal preference and riding style. In the photo above, Ted King is running Rene Herse 42 mm knobbies with Endurance casings, while I’m on 54 mm smooth Extralights. Perhaps my tires were a little faster, but Ted more than made up for that with his superior power. On the dry gravel that we encountered on that day in the heart of the Cascade mountains, the tread also made no real difference. It’s good to know that no matter which Rene Herse tires you choose, it’s hard to go wrong.

With wide tires, there are fewer compromises than in the past: supple tires are both fast and comfortable, and thanks to their low pressures, they also don’t get a lot of flats. More flat protection in the casing always comes at the expense of speed, but our goal in developing the Endurance and Endurance Plus casings with Ted has been to minimize these compromises. Our Endurance casings use the same ultra-fine threads as the Extralights, but in a denser, stronger weave and with a cut-resistant layer covering sidewalls and tread. Thanks to the high-end materials, the Endurance casings roll as fast as more economical tires with less protection – like our Standard casing or Schwalbe’s G-One Speed. Our Endurance Plus is one of the toughest tires you’ll find this side of tires for downhill mountain biking, yet it’s still surprisingly fast thanks to the high-end materials used for its construction. Our testing shows it’s faster than the OEM tires found on many production gravel bikes.

That also points to the downside of supple tires: cost. The best materials are expensive. The raw casings are fragile until they are vulcanized (baked) into a tire, so they must be handled carefully, by skilled workers. All that has a price, but we feel its worth the effort: A great, supple tire transforms the feel and performance of your bike more than any other component. That’s why we leave no stone unturned to optimize our tires for real-road riding.

Further Reading:

Ted King’s Water Cooler Talk about tires with Lael Wilcox and Jan as guests.
How to pick your Rene Herse tires? We help you choose the right tread pattern, width, casing, etc.
• Which Casing is Right for Me? More information about each casing.
• The Spring 2021 Bicycle Quarterly has the full test of our knobbies: How do knob height, wear, tire pressure and other factors affect speed.
• Our book ‘The All-Road Bike Revolution’ discusses the research that has revolutionized our understanding of how bikes work: tire performance, frame stiffness, frame geometry and every other aspect that determines the performance, comfort and reliability of your bike.
• More data that show higher pressures don’t make tires roll faster.
• We would like to see more real-road tests from independent researchers – a description of our testing methods is here, and Bicycle Quarterly 73 has an article on the subject with more details.

Thank you to Enve for the loan of several Enve 45 wheelsets that were used for these tests.

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Comments (51)

  • Mike

    Thank you for sharing your results. This is really exciting. Any thoughts about the Conti Terra Speed?

    April 5, 2021 at 4:55 pm
    • Jan Heine

      Our goal was to make our tires faster, so we mostly tested different casings, pressures, tread patterns and rubber compounds. We only looked at other tires to see how our tires stack up in the comparison, so we tested what we thought was the fastest tires out there, plus some OEM tires. The Conti Terra Speed was tested by GCN a while ago, and it seemed to roll a lot slower than Conti’s road models, so we tested the Schwalbe G-One Speed instead.

      April 5, 2021 at 6:14 pm
  • Ahmad Z

    Amazing set of data points Jan. I would like to suggest a journal post pointing out a ballpark figure for an optimum tire pressure on RH tires, instead of basing it purely on ‘feel’. Appreciate that there are many variables involved but a simple formula or algorithm (like an online RH tire pressure calculator) might do a decent job for starters. Thank you.

    April 5, 2021 at 7:09 pm
  • Jacob Musha

    Thank you for this thorough summary. The latex tube results surprised me. In the past I thought you found latex tubes to be similar or slower than butyl. What changed? If I remember correctly, latex tubes tested previously were thicker? Should latex tubes be lighter than butyl to be faster, and where can I buy them? 🙂

    One benefit rarely mentioned of wide Rene Herse tires is that they never seem to wear out! I must have >4000 miles on my first set of original 2016 Rat Trap Passes and there is still tread left…

    April 5, 2021 at 7:50 pm
    • Jan Heine

      We tested green and relatively thick latex tubes in 2006. The new ones were provided by FMB, but they don’t sell them – they only use them for their tubular tires.

      April 5, 2021 at 8:33 pm
    • Andrew Stow

      4000 miles is getting close to the limit. I got a Stampede Pass (32 mm) to nearly 3000 miles on the rear, and the tread was so thin I punctured multiple times on my nine mile morning commute, and walked the last mile. I had to put a few layers of duct tape around the inside to ride home. I’ve had a Barlow Pass (38 mm) on the front last nearly 5000 miles! The sidewall failed on that one (user error.)

      I’m currently running 48 mm René Herse, with a knobby up front and smooth in the rear, both tubeless. I bought one knobby just to try it and see if it fit under the fenders okay. I did not notice any change in speed when I put it on, just a whine at speed that isn’t unpleasant or loud. I now plan on putting a knobby on the rear, too, once I have some more stuff to order.

      I’m not a super strong rider, but I regularly cruise at 20 MPH on the flats with low wind.

      April 6, 2021 at 6:57 am
      • Jacob Musha

        The extra width of a 52mm Rat Trap Pass means a lot more rubber to last much longer than a 32mm Stampede Pass. I don’t keep exact records of how many miles are ridden on specific bikes, but it’s possible the tires have as many as 7000 miles… Though 4000-5000 is more likely.

        April 6, 2021 at 11:39 am
    • Frank

      Vittoria, Challenge, Vredestein and Michelin sell latex tubes. I have no personal experience with Vredestein; of the remaining I rate Vittoria the best, followed by Challenge.

      April 6, 2021 at 7:51 am
      • Jan Heine

        The problem is finding latex tubes for wide tires…

        April 6, 2021 at 8:24 am
        • Sam Atkinson

          Vittoria makes latex inner tubes for 1.7-2.3″ tires in 26er and 700c. They also make them for 30-38mm tires in 700c. I use the 26er tubes with my Rat Trap Pass ELs.

          April 6, 2021 at 8:35 am
          • Chris Grigsby

            I presume the Vittoria 26 1.7-2.3 would work for a 650b 42mm or 48mm tire?

            April 7, 2021 at 2:23 pm
  • Reuben

    For those of us on racing bikes:
    How do your 28 and 32mm tires compare with the industry heavyweights of continental gp5k, Schwable pro 1, specialized turbo etc…

    Thanks!

    April 6, 2021 at 7:39 am
    • Jan Heine

      That’s a good question! Of course, the advantages of developing our tires under realistic conditions rather than in the lab apply to narrow racing tires, too.

      We tested the FMB clinchers, because FMB’s cotton casing is known to be one of the fastest in the industry. (That’s why pros buy FMB tires with their own money for the really important races.) Talking with François Marie of FMB, he puts more rubber on the clinchers than on the tubulars – especially the inside – to protect them during mounting. (Nobody ever touches the inside of a tubular with a tire lever!) Our casings are made from synthetic materials, so they are stronger, and we don’t need so much rubber. We worried a bit that synthetic casings might still be a bit slower than cotton, but the tests indicate that our casings are comparable.

      Others have tested our tires against some of the ‘heavyweights’ and found them to be as fast or faster. And many customers are so excited about our wider tires on their gravel/all-road bikes that they try our narrower versions on their road bikes, and they report excellent comfort and speed as well.

      April 6, 2021 at 8:23 am
    • Jan

      Continental or Schwalbe are known for their Benchmark in rubber compound which of course has an big influence too. That’s why they perform quite well and better than other big brands, although the casting is more on the standard site and not that supple.

      April 7, 2021 at 1:05 am
      • Jan Heine

        The long-chain polymer rubber compounds that hide behind the colorful names aren’t trade secrets. We tested quite a few rubber compounds, including long-chain polymer based ones… We use the tread compound that rolls fastest on real roads.

        April 7, 2021 at 8:52 am
  • Vito

    Thank you for the great information. I’m due for new tries so this as made my decision easier. I live in Ontario Canada and was wondering who would I call that would would have stock 700c x 28 mm Extralights available?

    April 6, 2021 at 7:55 am
    • Jan Heine

      You can either order direct, or from a number of bike shops who sell our tires. In Ontario, Bicycle Specialties usually have good stock.

      April 6, 2021 at 8:24 am
  • Nate

    Nice to see that a product you don’t sell (latex tubes) scores better than the butyl tubes that you do sell.

    April 6, 2021 at 8:59 am
  • Tom Anhalt

    Can you explain the method you used for separating out just the Crr component from you coasting tests in order to create your “Flat Road, 150W” and “Flat Road, 400W” calculations? Also, in case you didn’t know, the http://www.analyticcycling.com site has been for quite some time now (unfortunately). Lastly, what pressures were each tire inflated to for the testing? That seems to be left out.

    April 6, 2021 at 10:48 am
    • Jan Heine

      We plugged the known values for the low-speed tests (including gradient and speed) into analyticcycling.com and solved for Crr. Then we used those values to calculate the speed differences between tires at higher speeds and on uphills. Yes, analyticcycling.com no longer is online. This research was done last year and published originally in the Autumn 2020 Bicycle Quarterly.

      All tires were run at optimum pressures. That ranged between 28 psi for the 48 mm tires and 65 psi for the 28s. The 44s that were used for most of the comparison were run at 30 psi. As we’ve shown before, tire pressure doesn’t make a big difference on real roads, but for the comparisons, we tried to run tires of similar size, at similar pressures, to eliminate that variable. (In some cases, like the FMB tires or latex tubes, we had to test what is available.)

      April 7, 2021 at 10:17 am
  • Eric

    As a random, semi-scientific data point, I’ve just put RH/Compass tires on my 26″ road tandem (XL Naches Pass on the front @40psi, Regular RTP @30psi on the back (the front was supposed to be a standard, but apparently I got a surprise upgrade)). This is the first time that I’ve swapped an existing bike over to these tires, so I have something of an apples to apples comparison. The previous tires were Schwable puncture resistant 40mm city tires, so not exactly supple. Previous rides with the same stoker were coming in in the 15-16mph range, with a top average of 17.2mph.

    In the three rides since, two have been above the previous fastest speed ever, and the one that wasn’t had a lot of climbing and was still quick. I’d say that the tires are worth between 5 and 10% in my usage. This is at or above what you’re saying in the article as an effect.It may be that the tandem is more sensitive because of the higher weights on the tire, and it may just be because the old tires were pretty stiff.

    Also, the stoker is pretty happy with a cushier tire in the back.

    April 6, 2021 at 2:07 pm
  • Toni

    Did you test wider tires than 44mm?

    April 6, 2021 at 5:35 pm
    • Jan Heine

      In this test, we tried running 55 mm tires, but they rubbed on the frame of the test bike. We tested our 700C x 48 mm Oracle Ridge knobbies, and they rolled a little bit faster than our narrower knobbies. We suspect this is because with wider tires, the weight of rider/bike is spread over more knobbies.

      In the past, we’ve tested smooth 48 and 54 mm tires with a power meter. They required the same power as our narrower tires, but there is more noise in the data when the rider pedals. If the 48s or 54s were slightly slower or faster than the other tires, we might not pick that up with that test. That’s why we refined the methodology and didn’t report the old test results here.

      So in short, there is no indication that tires up to 54 mm roll slower than narrower tires.

      April 6, 2021 at 9:08 pm
      • Nick Larson

        You quote 1% as the difference you might not pick up. All of the values you list have two decimal points, well below the 1% threshold. Do you ever run your tests with replicates to get a better idea of the standard deviation of your measurements to get an idea of the significance of your tests? Putting error bars on these graphs would help you/others understand which differences meaningful.

        April 7, 2021 at 5:54 am
        • Jan Heine

          In our previous tests, we couldn’t pick up a 1% difference – that is why we refined the method (and didn’t include the results of the previous tests here). The results shown are averages of multiple test runs. We show clearly which results are statistically significant and which aren’t.

          I agree, though, that the second decimal point could be deleted – reporting the results to tens of seconds wouldn’t change anything. If we publish the data again, we’ll do that.

          April 7, 2021 at 8:10 am
  • Eric

    I was a little confused (maybe disappointed) in the print article to read this, and I see here as well. You use scientific jargon yet you don’t actually show us statistics or replication. In fact, this “Small gaps between the bars mean that the differences are not statistically significant. Large gaps mean they’re significantly different” which is total” is total mumbo-jumbo. That’s why we have statistics and why you plot confidence intervals – small differences may be significant if that measurement was extremely consistent and variance is low, large differences may not be if the measurements were all over the place. Averages (or maybe, a single point) do not tell much of a story.

    I got the sense that you may have done a lot of these comparisons once and therefore, you are being somewhat disingenuous using these statistical terms, since it has a specific meaning (which I suspect you know). I think I speak for many bicyclists with engineering or science backgrounds when I say we would like more information on your testing, sample sizes, and stats. It doesn’t need to be a scientific article, but you footnote all sorts of minor points in BQ; this would be appreciated. As is, I’m not treating these produce placement articles as more than an infomercial with some excel charts thrown in.

    I love the magazine, get excited every time it shows up in the mailbox, just would get a lot more out of these tech articles, and be more convinced to actually buy RH tires, perhaps, if I could evaluate these tests a little better.

    April 7, 2021 at 5:45 am
    • Jan Heine

      Sorry for the misunderstanding. We did the statistical analysis, we just didn’t publish it this time. We published it in the past, but most of our readers aren’t interested in those details. If we give over the entire magazine to tire testing, and no longer publish adventures, ride stories, shop visits, etc., we don’t serve our readers well.

      April 7, 2021 at 8:15 am
    • Nate

      I’m a bit surprised by all the commenters who complain about a lack of error bars, and that the statistical analysis isn’t published. When did you last see error bars and statistics in a bicycle publication, especially online? Usually, we see two measurements, and the conclusion is ‘A is faster than B.’ Here at least there are repeat measurements, statistical analysis has been done, and the limitations that some results are not statistically different are clearly acknowledged.

      As Jan mentioned in the post, the goal is to make better tires. Anybody can ride the tires and see if they agree with the RESULT of the testing. For my part, I have to say that I do. I’m glad Jan and the team report on how they arrived at those results. But in the end it’s all about the ride!

      April 7, 2021 at 8:19 am
  • Chris Grigsby

    Does anyone make a latex tube for your 650b 42mm-48mm tires? I can’t seem to find one, but would love to try it out.

    April 7, 2021 at 6:00 am
  • Steve

    Brilliant article, thank you. Ahmad Z mentioned tyre pressures, maybe ask users to send data (for me 95 kg gross weight, 25 – 30 psi with RTPs on tarmac and gravel road)?

    RH slicks have file tread on the shoulders for cornering, is there any advantage in having the same on the shoulder knobs of knobbies? This leads to another question, would cornering change any of these results (not many straights nor flats where I live)?

    April 7, 2021 at 6:29 am
    • Jan Heine

      We thought about adding a file tread to the top of the knobs, but there isn’t enough surface area for that to work well. The knob edges already provide a lot of interlocking surfaces, so the cornering grip is surprisingly good. In fact, I can’t say they corner any worse than the slicks…

      April 7, 2021 at 10:41 am
  • Jeff

    In all the tests where you are comparing different tires, I would like to see you specify what pressures you were running them at. While you show that the pressure makes little difference for the super-light casings, that is not necessarily true of other casings. To be a meaningful comparison, each tire should be run at the optimum pressure, or at least have it specified. Can you give this information?
    Thanks.

    April 7, 2021 at 7:33 am
    • Jan Heine

      The information is in the original articles in Bicycle Quarterly. There were already too many numbers in this Journal entry. We ran all tires at optimized pressures, which ranged between 28 psi for 48 mm tires and 65 psi for 28 mm tires. The 44s that you see mentioned a lot were run at 30 psi. For the comparison of different tires, we also tried to use similar sizes, so we could run similar pressures. There’s a lot more data than we can show here – for example, we directly compared the WTB Raddler against the Rene Herse Steilacoom Endurance (both about 38 mm actual width) to get a more direct comparison. The results were the same, so we didn’t report this (and many other tests we used to confirm our initial results).

      April 7, 2021 at 8:28 am
  • randfein

    As the available supple road tires have gotten wider over the last twenty years, so have mine, first (for me) through Vittoria, then Challenge, an now Rene Herse. As I’ve adopted wider road tires, I’ve noticed they take a bit longer to break in than skinny’s. My most recent RH tires with endurance casings (several sets between 38 and 43 mm) seem to have gotten a bit more supple and faster over the first, say, 200 km, whereas I’ve sensed about half that distance for 25 mm Vittorias. Is it just my own perhaps faulty perception, or have you also noticed (or even been able to measure) a break-in period? It makes me wonder whether tests of brand new tires (as opposed to tires already ridden for 200 km) would even put wider tires at a disadvantage when they’re compared to narrower tires in roll-down tests. Similarly, whether the difference between RH Extralights an Endurance casings are overstated if the latter take longer to break in.

    April 7, 2021 at 7:41 am
    • Jan Heine

      We tested new vs used tires in a previous test – with power meters – and there was no significant difference. That doesn’t mean that tires don’t break in, but the effect was too small to detect with the methodology we used. In the current tests, we tested knobbies with 500 miles against new ones, and the used ones were significantly faster at slow speeds. It appears that the knob edges round off and flex less as the tires wear.

      April 7, 2021 at 8:24 am
      • Gunther

        This looks like a point of possible improvement in future products: built-in rounded knob edges right out of the factory.

        April 7, 2021 at 1:02 pm
  • Stuart Fogg

    Not 100% on topic, but do you notice a difference in rolling resistance between bikes with the same tires but different fork/frame stiffness? I’ve heard that suspension bikes are faster on really rough surfaces so I wonder if frame compliance is significant on roads.

    April 7, 2021 at 8:45 am
    • Jan Heine

      That is a factor – suspension losses are important even on smooth roads. We tested that when we tested suspension losses, and we found that a very stiff fork was slower even on ultra-smooth pavement. But that’s a topic for another day…

      April 7, 2021 at 8:47 am
  • J G White

    Thanks for posting this info; very interesting. I for one am thankful that you omitted the underlying details of the statistical analysis.

    I’ve been enjoying the endurance casing variant of the Switchback Hills on my touring and “adventure” bike. Such a nice change from the heavily armored touring tires that I’ve used in the past. Will be interesting to see how they hold up over time, but early indications are promising. So I love the darker tan/brown sidewalls of the endurance casing (even better than tan)…looks great on my bike and, hey, that must be worth a few extra mph! 🙂 In any event, I found your discussion re pressure interesting as I’ve had to do a little experimentation to dial in the optimal pressure on the Switchbacks….at least compared to “not supple” touring tires I’ve used in the past.

    Re latex tubes, I’ve been running some Silca latex tubes w/ Conti GP5k tires (28mm, 30.5mm actual) and I think I can say the setup is a bit better than standard butyl tubes. On a different wheelset, I am getting ready to experiment w/ road tubeless using the WTB Exposure tires at 30mm. After reading your testing summary, one might say why bother….but getting first hand experience is usually good. If it’s a failure, then I will just put some tubes in.

    Any thoughts on the prevailing wisdom re the ultralight “plastic” tubes such as Schwalbe Aerothan and the others? Indications seem to be that latex may outperform those. But the ultralights may be good spares for those running minimalist setups.

    April 7, 2021 at 9:25 am
  • GD

    For faster riders averaging 20+ mph, what can we take away from your research? It sounds like you have data on aerodynamic loss with higher speeds, do you plan to publish this or provide insight? Should these faster racer type riders be riding a 44mm slick or should they be on a 35? or 28? Would love to understand what tire would be best for say a 28 mph criterium or a 25mph road race.

    April 7, 2021 at 9:55 am
    • Jan Heine

      The 400 Watt comparison in the post has you at speeds of 25 mph. (Sorry, the values are in kilometers.)

      To your specific question: For a road race on smooth roads, 25 mm tires are optimal, since they are lightest and don’t roll slower than wider tires. If the pavement is rough, you should go wider. How wide? It depends on the pavement! In the end, going wider won’t hurt you, so I’d err on the side of wider tires. For our average country roads that are used for American amateur racing, I’d probably choose 32s.

      April 7, 2021 at 10:12 am
  • Herwig

    Dear Jan,
    thank you for sharing the results. I am wondering about your figure, or rather sketch, resistance vs. tire pressure with the buckle. I remember seeing a similar graph from your source that shows a dip in a middle pressure, stating too low pressure gives high resistance (as is also shown in your plot of the Hurricane Ridge Extralight tire pressure series), a medium pressure gives low resistance and high pressure then increases the resistance again.
    Are these statements contradicting or is the original figure with the dip for medium pressures incorrect? I just wonder if this can really be true. To me it does not make sense, honestly. Because ultimately, this would mean that you would be faster on steel tires, which we all know is not true.

    Maybe you can enlighten me a bit more.

    Cheers

    April 7, 2021 at 10:59 am
    • Jan Heine

      Our conceptual graphic above doesn’t include the very low pressures – which are slow and unsafe. Also note that the high pressures aren’t faster than low pressures, even on very smooth pavement. On rough surfaces, low pressures are always faster. Maybe that’s a topic for another Journal post…

      I’ve seen graphs online that show medium pressure rolling faster than high pressure, but it was unclear how these results came about, and whether they were statistically significant. They don’t seem to match our data – not just from this one test, but from numerous others as well.

      April 7, 2021 at 2:27 pm
  • calcagnolibero

    Thank you for sharing the results of your study.

    April 7, 2021 at 1:10 pm
  • Marius Clore

    Interesting results but not quite on the level as I guess you are using box rims throughout in which case there are no aero gains to be made. However, I would wager that if you tried different width tires on say an ENVE SES 3.4AR or the new Zipp 303 tubeless, you would find a big difference between 28 mm tires (the width that the wheels are optimized for) and a 40 mm tire where all the aero advantage of those wheels is effectively gone.

    April 7, 2021 at 1:49 pm
    • Jan Heine

      We ran these tests with Enve 45 rims, not box rims. You can see the test setup in the top photo.

      April 7, 2021 at 1:55 pm
  • D.Rabes

    I’m a bit confused, if knobby performs about the same as smooth why bother even making smooth tires?

    April 7, 2021 at 3:15 pm
    • Jan Heine

      Good question! They actually behave differently. The knobbies have less pneumatic trail and thus less straight-line stability. That may be good or bad, depending on your bike’s geometry. Knobbies also don’t work well with fenders. And finally, with less rubber on the road, knobbies wear a bit faster…

      April 7, 2021 at 4:14 pm
  • Alex Markham

    One thing I’ve noticed on my Juniper ridge 650b x 48mm extra light is that they roll well, but under a lot of non-smooth power or bounce (such as when standing up on a steep climb) the tyres add a light bounce, similar to a suspension bike.
    This bounce doesn’t happen on small road racer tyres. Could that bounce sap energy in a similar way to riding a full suspension mountain bike does, or is it all imagined? (like the feeling of a too stiff bike frame vs a flexible/planing frame)

    April 7, 2021 at 3:34 pm
    • Jan Heine

      There’s definitely some flex in wider tires. That can be beneficial or detrimental. It’s easy to tune that via the tire pressure – if you want less flex, just increase the tire pressure!

      April 7, 2021 at 7:11 pm

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