wide road tires
  • Great discussion, James, Jan and Josh!

  • Jim

    32mm ? That’s not going to fit under the brakes/fork – not by a long shot.

    New bikes all round – happy days for the bike shops / brands.

    • ebbe

      You know you don’t HAVE TO do 32mm, right? ;-)

      But if you can, or you’re planning to buy a new bike anyway, this is good info

    • James Huang

      Of course, many bikes aren’t equipped to handle some of the tire sizes being discussed in this podcast. To be fair, no one here is saying that you need to buy a new bike (and notably, neither of our guests this week have any stake in bike sales). It’s mainly just something to think about, and perhaps something to consider if/when you start looking for something down the line. Given the direction road bikes are already heading in, though, my guess is that more generous tire clearance will soon already be included in whatever is offered.

    • Michael Cambron

      It’s very easy to experiment by buying a 1970 or early ’80’s lugged steel road frame. Most of the racing frames from that period could easily handle 32mm tires.

    • Morten Reippuert Knudsen

      32? go 35mm or even wider – size matters. Unless you race you will appriciate it.
      I love my new 9kg custom chinese Ti disc-brake bike with a chorus/sramXO/XTR/TRP/wipperman bastard-groupset with its DT460db/DT180cl wheels and 35mm Compass Bon John Extralight’s.

      Since i’ve got it, i have hardly ridden my beautifull re-finnished sub 7kg 2006 Merlin Works CR (1100g)/ Chrorus 2015 / 2012 Reynolds FortySix/Sixty & 27mm Vitorria Pave tubs – The Merlin accelerates signifiantly easyerer and maintains high speeds way betterdue to both weight and arodynamics, but those 303g 35mm wide tubeless tyres are just so damm nice and fun.

  • velocite

    Thanks for this, very interesting. So interesting that it’s worth an article, with links, for example to the details of the rumble strip test, and also to the resources Jan Heine mentioned towards the end. An article would also give the author/editor a chance to address some of the contradictions and inconsistencies in the views expressed at different times. I know it would cost, but I dislike podcasts. Individual points are inaccessible, you can’t scan it, you’re stuck with investing 48′ into listening to it.

    I’ve used Frank Berto’s 15% drop chart to set my pressures for a long time. Currently on 25mm Schwalbe One tubeless I run 90 rear/80 front. After listening to this I’m going to drop 10 psi and test, and maybe repeat. For my next bike I’m thinking 30mm may not be enough.

    • Doug M.

      Ruble strip tests are in BQ #29 (https://www.compasscycle.com/shop/print/issues/bq-29/), but this article on Jan’s blog covers a lot of it: https://janheine.wordpress.com/2016/06/14/suspension-losses-confirmed/

      • velocite

        Thanks, it just took me 2 hours to read the janheine post, all of the articles which linked from it and all of the comments! What’s missing is an app into which I can enter all may parameters and get an answer about tyre width and pressure on each wheel. One of the inputs will need to be an indicator of the road surfaces I ride on, preferably numerical. I imagine a device towed at an accurately controlled speed over a stretch of target road which will measure the roughness/smoothess.

        BTW, the first link goes nowhere – but the second one more than made up for it!

        • Rider_X

          > What’s missing is an app into which I can enter all may parameters and get an answer about tyre width and pressure on each wheel

          Width: As wide as your frame can handle.
          Pressure: As low as you dare, until your cornering is affected.
          Tyre suppleness: As supple as you can afford.

          Until we have road bikes that can clear huge tires (i.e., 50 mm)

          • velocite

            On very smooth roads at high speeds I don’t believe it, and not because I personally am seduced by high frequency vibrations. Heine’s rumble strip test was brilliant, but I didn’t see any actual tests that supports your ‘general rule’. Poetner’s charts, methodology unknown, actually show an optimum of 100 psi, but it’s hard to work out the significance of that. It seems to me that these guys have carved out a discussion space which is waiting to be filled out, for more factors to be quantified and related. Suppleness of tyres? As Heine says in an article, thread count is not a reliable guide to tyre suppleness, but we don’t have an index for it. I believe that wider tyres on aero wheels have offered less air resistance because of an improved rim-tyre junction, but there will be a limit, of course.

            More charts!

      • ZigaK
        • velocite

          Thanks for that corrected link. Problem with Doug M.’s was a rogue trailing parenthesis.
          As it happens, I’d already read that post by following links from the janheine blog.

      • The biggest problem I have with Jan’s findings is that none of the tests have been done in a closed environment. Repeatable findings that can be replicated by others under controlled conditions are very important. This is akin to having a single study telling us that beer is terrible for us – it’s very important that it was done, but it needs to have additional studies under controlled conditions (e.g. in a lab).

        • Doug M.

          There are indeed thousands of potential confounding factors. I’m sure Jan & co. would be glad to apply for your funding of a lab-controlled study [/tongue in cheek].

          It strikes me that they did the best they could with resources at hand, and if nothing else, are probing for practical limits where others had not before.

          • Absolutely, and I agree – they did the best with what they had at hand. That’s generally what the early studies are and need to be, otherwise research money is spent poorly. What I’d really like to see is for a tire manufacturer to step up and fund some serious testing under as controlled an environment as possible, potentially with a team of riders and/or wind tunnel time. The sad truth of this is that it could get very, very expensive very quickly.

        • Marco

          The tests done by Bicycle Quarterly are done in the most possible controlled conditions the environment allows. Then a statistical analysis is made on the results to assure that the results are statistically significant. More info on these articles:




          • I’m very familiar with Jan’s work, being that his findings were published years ago, which is why I am not saying that it’s to be discounted or fallacious – it’s very noteworthy and potentially groundbreaking. That being said, it’s the same as drawing conclusions from a single study without peer reviewed replication. In every other industry that would be cause for scrutiny and additional testing; not only that, but advancements in technology are usually made by these peer reviewed studies. Joshua Poertner’s addition to this should be considered invaluable as well, but it still needs a little more.

        • Rider_X

          Closed environments are not a panacea. Lab test results can misinform if they do not adequately replicate or capture important factors that occur under real application. Suspension losses (rider vibration) is such factor that is often not included in lab studies. The argument, is that lab testing of tires have for many years ignored a massive lurking factor (rider/bike interaction).

          Empirical approaches are fine, but may simply require more replication than lab test so you can control for measurement error (i.e., random error introduce by conducting the test in an open environment). The BQ experiments showed repeatability (despite being conducted in an open environment), and statistically significant differences existed after controlling for measurement error.

          • That indicates the metrics for which lab testing is currently done is wrong, which is somewhat at the heart of what I’m trying to get at. Peer reviewed studies, gathering as much data and having as many eyes looking at it from as many different perspectives as possible, with industry people paying attention to it – that would lead to changes in development and manufacturing and a new bar that we use to compare tires against for what is fast (and, from the SIR handbook, consequently what will go farther easier). We’d all benefit from that.

    • Anon N + 1

      “I dislike podcasts.” I second the motion. I’d rather read an article. In fact I didn’t waste my time on the podcast but read the intro and went straight to the comments which contains links to the relevant information.

  • Mike O’Hanlon

    The problem I have with this is very simple. I have been cycling for rather more than fifty years and I have found that narrower tyres running at higher pressures are always faster on hard surfaces.

    • Doug M.

      As proof is indeed in the pudding, I recommend trying a nice >= 28 mm tire. I postulate that it will be interesting, at least.

      • Mike O’Hanlon

        When I started cycling, the narrowest beaded tyre available was 1 1/8 inch i.e 28.575 mm, recommended pressure 85psi. We rode tubular tyres for racing. The fastest tyres I ever experienced were 18mm silk track tubs which we ran at around 150 psi.

    • Wily_Quixote

      did youlisten to the podcast? The first 5 minutes addresses the perception of speed

    • Hamish Moffatt

      The podcast is aimed at you exactly then Mike. They talk about exactly this.

  • ebbe

    For those reading this that don’t use Pounds and Inches (which should be forbidden anyway), and prefer bars (also not preferable) or kPa (preferable)
    PSI = BAR = kPA

    40 = 2.757898 = 275.7898
    50 = 3.447372 = 344.7372
    60 = 4.136847 = 413.6847
    70 = 4.826321 = 482.6321
    80 = 5.515796 = 551.5796
    90 = 6.20527 = 620.527
    100 = 6.894745 = 689.4745
    110 = 7.584219 = 758.4219
    120 = 8.273694 = 827.3694
    130 = 8.963168 = 896.3168
    140 = 9.652643 = 965.2643
    150 = 10.342117 = 1034.2117
    160 = 11.031592 = 1103.1592

    • Laurens

      Hear hear! It’s not just a matter of taste, metric is just so much better! I can’t believe how many people are so afraid of change that they want to ignore those benefits.

  • Jason Dwyer

    found the frank berto tyre pressure doc they talk about here: http://www.bccclub.org/documents/Tireinflation.pdf

    i get pretty lazy and sometimes go a good month ( ~1000km ) without checking presssure, then find it down in the 40psi range, yet my ride times dont seem to be any different.

    i’m ~73 kg + an 8.5kg bike with somewhat exotic tyres ( specialized roubaix 25mm width, 28mm ‘height’ ) and i’ll pump for ~85psi by default.

    that chart tells me i should be looking at something more like 65psi !

  • Ali89

    How is all of this affected by the age of the tyre though? As tyres age the rubber gets harder doesn’t it? certainly feels that way.

    • James Huang

      Good question, and I’m not sure. I’ll see what I can find out.

      • George Darroch

        Tyres increase in size with both age and at higher pressures. A one year old 23mm GP4000S at 100psi is going to resemble a 26mm tyre. Can’t remember the exact source, but believe I read that via a link on Slowtwitch.

    • Michael Cambron

      The good tires they speak to in this podcast won’t ever get old if you ride 3,000+ per year…

  • Pedalbot

    Great podcast. Too bad many of the manufacturers now supporting larger tires have gone all disc without a standard brake option (even long reach brakes).

    Also, I’m surprised on the recommendation to use latex vs. butyl tubes. I thought the latest convention was that latex didn’t make too much difference and are more trouble than they were worth?

    • James Huang

      I hadn’t heard that at all in regards to latex vs. butyl tubes. Older latex tubes were often pretty unreliable but modern ones are quite good, and all the stuff I’ve seen with respect to rolling performance says they’re much better than butyl.

    • lowlander

      Latex tubes are great but have a bad rep in some circles. The biggest problem as far as I can tell is that people commonly pinch them under the tire bead which can result in a sidewall blowout. (More rare, but can happen with butyl as well) Simply adding some air to the tube to give it some shape prevents this problem. The other tip is to have quality/well installed rim tape.

    • velocite

      I thought that the problem with latex tubes was that they lost air too quickly due to relatively high permeability.

      • James Huang

        They do, but because they’re so flexible, they are also a little more prone to installation error.

  • steinmetz

    I have a few questions. Were all the tests done on a flat road? I would think one would go much slower climbing hills, especially if you stand a lot. Would you lose a lot of power if the tires absorb the up and down weight of the rider when standing?

    Another question is that most road tires I’ve used have a MINIMUM tire pressure rating, e.g., 90psi. I’ve seen the same with rims–many spec a minimum of 90psi, especially for tubeless road rims. Should I be concerned lowering the tire pressure beyond what the manufacturers recommend?

    • Aeyockey

      Fo the pressure: They talked a bit about it but if the pressure is too low then the tire can roll off the rim or pinch flat with tubeless that’s the when the “burp” happens. The manufacturer’s probably have to specify that so if you are injured when the tire comes off you can’t sue them. Ask any cyclocross racer and they will tell you to ignore the specified minimum.

    • Arfy

      If you’re riding out of the saddle on climbs then you really want to develop a smooth pedaling style so you don’t “bounce” as this is extra energy you’re using to not go anywhere regardless if the tyres absorb the energy or not. I find I’m better staying seated on climbs, I’ll generally get about 50W extra in the saddle even though it doesn’t feel like it.

      Regarding PSI, the minimum pressure should be set based on the maximum deflection allowed for the tyre to prevent pinch-flats or rolling off the rim. I was puzzled by this question until Lennard Zinn asked some tyre manufacturers for me, as I’d been given the sales-speak of “don’t go below the rating of the tyre” when my 25mm Vittorias were rated at 115PSI min!! I did my own deflection test at home, and found that the tyre deflection was pretty linear until I got down to 60PSI when it really dropped off sharply, more surprising was this was very similar for both the Vittoria racing tyre with high TPI and my solid bullet-proof Gatorskins. As a result I run my front at 80-85PSI and rear at 85-90PSI without any issues, and you could go lower if you’re lighter (I’m about 82kgs).

      • steinmetz

        Thanks for the response and advice guys! I only weigh in at 52kg, but running 90psi in the rear and 85 in the front. I will try to go lower and see what happens. Are you at all concerned about getting snake bite flats with such lower tire pressures?

  • Stephen J Schilling

    Regarding the section of “suspension loss” @ ~16mins, was this ‘loss’ tested against diff frame materials? Does the natural damping of steel offset that energy drain, as opposed to a stiff, compliant carbon? What about Alu? Ti? And if that is the case, is it really the tire pressures, or is it the sum of the entire system?

    • James Huang

      Josh goes into quite a bit of detail on the flex characteristics of various frames on the Silca journal. In short, he says it’s a very, very minor part of the equation, and far eclipsed by the effect of the tires.

    • velocite

      Have a read of the link to Jan Heine’s blog in Doug M’s answer to my question below. His tests established that changing tyre pressures has a significant impact on ‘suspension losses’. Nothing else was changed. In another blog post Heine discussed the importance of supple tyres: https://janheine.wordpress.com/2015/01/05/tpi-and-tire-performance/. The effect of fork stiffness and even suspension forks is considered here: https://janheine.wordpress.com/2012/08/12/suspension-losses/

    • Rider_X

      Road/tire interface is the best place to attenuate vibration. The amount of frame flex is relatively small compared to the amount of tire deflection that is possible. Plus steel, carbon, aluminum frame compliance is more related to manufacturing processes rather than frame material as compliance can be built into all three technologies (i.e., steel: butting and tubing thickness; carbon: layup; aluminum: alloy and tube shape).

      Tire suppleness and tire pressure is really the primary driver.

  • Micky D

    James. Great work on the podcast. Really interesting to get a range of views not driven by company marketing. One question I have for you relates to the Frank Berto chart. He recommends a 20% difference in tyre pressure from front to back which is considerably more than I have seen on other recommendations. This seems to assume the weight distribution of the bike is constant when in fact it changes depending on road gradient, cornering and power load through the rear wheel.

    What is your view on the front/rear pressure differential?

    • James Huang

      Typical static weight distributions on a road bike on flat ground are around 40% front, 60% rear. Indeed, that figure will vary depending on the factors you mentioned but it’s a good baseline to work with. In any event, that 20% differential is more than I’ve historically used myself but it doesn’t seem outlandish to me. I’d say it’s just another area in which to experiment a bit to see what works for your particular case.

  • andygowans

    Would love to have heard more on the aerodynamic cost of wider tryes. There must be a tipping point where drag is high enough to make wider slower by offsetting the gains made in suspension loses? Not that I think it matters much. I ride the fattest most flexible road tyres I can fit in my frame. Comfort and grip wins out for me. But for those racing the clock aerodynamic matter.

    • Martin Dalitz

      Yep. And I can follow their reasoning about the benefit of lower pressures in terms of energy loss, but why is a wider tyre better. Weight, aero, distortion when climbing ?

      • Sean Doyle

        Because a wider tyre at 60psi ( for example) still has some volume and shape compared to a narrow tyre. The clue is in the units you are measuring with. Assuming a 120 pound rider/equip and equal fore/aft weight bias (unlikely). Each wheel carries 60 pounds load. At 60psi the tyre will deflect until the contact patch equals one square inch. At 70psi the contact patch is smaller at 50psi its bigger. A smaller section tyre has to change shape more to achieve the one square inch contact patch where as the bigger tyre less in relation to its cross sectional area. This flexing of the casing is what absorbs energy.

  • This is a worthwhile discussion of wider tires and lower tire pressures and their benefits in lowering rolling resistance. It’s a shame however that the discussion of the trade-offs between rolling resistance and aerodynamics isn’t more fully explored beyond the brief mention by Josh about 47 minutes in.

    A shame because, for most setups that the kind of enthusiast level cyclists who probably read CyclingTips use and at the speeds we ride, and contrary to what the podcast suggests, you won’t go faster by merely going with wider tires at the same or lower pressures. In fact, the rolling resistance benefits of putting 25C and 28C tires on most of the rims enthusiasts ride will usually be outweighed by the negative effect on aerodynamics of having a tire too wide for your rim and make you slower overall. If too wide and at too low a pressure, handling performance can actually get worse and the chance of you flatting can significantly increase.

    I’ve researched and written up these interrelationships along with some practical advice for roadies using the 15C and 17C wheels that are sold on new bikes and as upgrades today and even those who have found their way to the latest 19C and 21C road wheels (https://intheknowcycling.com/2016/04/03/best-wider-road-bike-tires-wheel-sizes/). Josh has more recently written a journal piece with more technical detail (https://silca.cc/blogs/journal see Part 5) about this is and why, if you want to go your fastest, you want your external rim width to be greater than your actual mounted and inflated tire width. Josh calls it the 105% rule and most of the leading road wheelset companies continue to make their wheels and recommend tires with this rim to tire width relationship in mind.

    • Marco

      I quote from Jan Heine Blog ( https://janheine.wordpress.com/2016/08/19/panel-discussion-the-wide-tire-revolution/#comment-22025 )

      “We tested a lot of those things in the wind tunnel – see Bicycle Quarterly 21.
      Wider tires make little difference – both with an without fenders, the
      difference between 25 and 31 mm tires was too small to be statistically
      significant. Good fenders are neutral, too – no increase in drag. The
      front part (in front of the fork crown) decreases drag, the rear
      increases drag, so if you want to go faster, install fenders that only
      extend forward of the fork crown.

      Generally, a cyclist is not a very aerodynamic shape, so it’s the
      frontal area more than anything that determines wind resistance. When
      you at a bike that way, 20 mm extra tire width makes little difference.
      Probably less than 20 mm wider handlebars…”

      • Marco, You are quoting Jan’s findings on the aero performance of the tire alone. It’s the aerodynamics of the wheel and tire together one needs to consider versus the rolling resistance of the tire. The added drag of a tire that’s too wide for it’s rim will be greater than the reduced rolling resistance (both in measured in watts) of a wider tire on rim that is mid depth (35mm to 50mm ) or deeper (50mm+) and rolling at 18mph/30kph speeds and up.

        Why? With the narrower tire than rim, the wind continues along the rim after it leaves the tire continuing an relatively undisturbed, mostly laminar aero flow; with the wider tire than rim, it never attaches creating, disturbed, turbulent aero flow. Best solution? Wide tires and still wider toroid rims which is why you are seeing some road wheels made with 28mm wide rims now for 25C tires (most which will measure close to 26-27mm wide once mounted and inflated at 80-100 psi, wider still once they stretch out after a few hundred miles of use). Steve

        • Rider_X

          > mostly laminar aero flow

          I thought laminar flow was a yes/no affair, either you have laminar flow or you do not. Is there an in-between state?

          Anyway, you are correct to point out studies into tire width and the optimal TT setup hasn’t been openly published (I assume some times must have studied this). At higher speeds on very smooth roads these is the possibility of going too wide for currently available rims. That said, most races are run on less than glass smooth roads, so rolling resistant loss may still be bigger loss than aerodyamic losses.

          One of the main problem is most race frames cannot run bigger than 25 or 28 mm tire – so you can only test a small difference in widths. I have been running a supple 38mm on one of my road bikes and I couldn’t measure a speed loss on the smooth flat. On most roads I ride, it was much faster.

        • Arfy

          From an aerodynamics point of view, I’d assume a wider rim (with a suitably wide tyre) needs a deeper rim profile than a narrower rim (with a suitably narrow tyre) to achieve the same rim shape and aero performance? In which case a narrow rim/tyre combo on the front could be advantageous on windy days?

  • Nick Orloff

    Great podcast, really enjoyed the discussion and I started experimenting on the weekend with lower pressures.

    The discussion seemed to say on a very smooth surface that higher is better – so do I start playing with pressures on my track bike as well as the road bike(s)?

    • James Huang

      I would, especially if your track bike is fitted with a power meter. “Smooth” is a relative term, after all, and while track surfaces are generally much smoother than anything you’d find on the road, it still isn’t a sheet of glass. Riding the track with a power meter is an outstanding way to gauge the real-world effects of something like this.

  • Doug M.

    Critique of research methodology aside, I’d just like state the obvious: that we don’t ride our bicycles in labs, and that ultimate speed is not the ultimate prize. Being able to enjoy a ride with friends, in relative comfort, and on multiple surfaces is reward enough. If you have the means, try a wide supple tire, pack a few extra sandwiches and extra clothes, and go somewhere rad :-)

  • Legstrong

    James, I haven’t listened to the podcast. It is blocked here at my office. I will listen it once I get home. I have this long standing question before I forgot it when I get home.

    I assumed (judging from the comments) the discussion mainly focused on the tire rolling resistance not the aerodynamic. Per Mavic’s engineering discussion (link below), “So, widening the rim for aero benefits is really efficient as long as the tyre remains narrower than the rim’s widest point.”


    Therefore, you should fit the widest tires per your rim width specs, am I correct?

    • James Huang

      Correct, this discussion focused almost exclusively on ride quality, grip, and comfort, not aerodynamic performance. That said, Mavic’s guidelines in regards to tire vs. rim width with respect to aerodynamics is inline with what Josh Poertner recently outlined in one of his blog posts on the Silca web site.

      • Legstrong

        Thanks for the response James. I had listened to the podcast since then. It was a great knowledge transfer.

  • Robert Merkel

    Yes, excellent discussion. Thanks!

  • Alex

    They recommend buying latex tubes. Previously latex tubes were recommended against with carbon clinchers due to heat buildup issues. I’m wondering if this is still the case with these newer generation of rims that are supposed to be able to handle higher temperatures?

  • Benny Watson

    With the advice to “Buy the nicest, most supple tires you can afford; and buy them in the widest width that you can fit in your frame.”, what defines a supple tire and other than Compass, what are some good examples?

    • Michael Cambron

      I would put Continental Grand Prix & Challenge Paris Roubaix in this category. I use the Compass Extralight Stampede Pass and they are quite supple. I’m approaching 2,800 miles on them and I’ve been quite happy. I started off inflating them between 60-70psi but I now run them between 50-55psi. I also ran them once too low and experienced sidewall collapse. Unfortunately, I don’t know the pressure when that occurred but I’m pretty confident it was below 40psi.

  • I loved the discussion in this podcast, as this is clearly an issue where what we in psychology refer to as experiential vs rational processing or decision making. I imagine that because the level of measurement, and analysis required, for rational processing and analysis about going faster is so much for almost everyone, then the majority of us are quite happy to default to experiential processing in this instance of higher pressures feeling faster.

  • P3N54

    I guess one point that was left out of the discussion so far (or I have missed it) is that, certainly for racing types, the higher weight/higher accelerated mass of wider tires is a concern. Therefore, you could extent Jan’s decision tree by adding a course profile, ride type or “dominant use” decision so you’d use a wider tire for a flat, no turns out and back TT and a narrower tire for a race with lots of climbing and/or changes in direction where the cumulative effect of accelerating a higher mass out of corners makes a difference over a couple of hours (assuming it makes sense from a road surface perspective)

    Also, the current discussions are assuming that we are putting old-fashioned air in your tires while all the cool kids are using helium or lighter gases for racing/climbing/TTs. Would be interesting to understand if that changes the overall dynamics.

  • Kevin

    In my experience the major limiting factor in getting people on board with this is cost. Most people I ride with buy one, MAYBE two, sets of tires each season. Frequently these guys are buying the exact same tire season after season – it’s tough to break that habit. It’s especially hard to break that when they are already frustrated with shelling out $100+ for a pair of tires – they want to ride what they know has worked in the past and not potentially waste money on a tire setup that they don’t trust – regardless of the science.

    • James Huang

      Agreed, tires – especially good ones – are awfully expensive. That said, it costs nothing to experiment a little with tire pressures, and a small change can yield a big difference in ride quality.


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