What’s The Fastest Tyre Pressure For Cycling On Cobbles?

What’s The Fastest Tyre Pressure For Cycling On Cobbles?


– If we look like we’ve
just done Parriere Bay, we kind of have. This morning we set out
from the Arenberg Forest to look at the final
100k’s of this year’s race, a video which you will hopefully see soon, if it’s not out already. But now we’ve arrived
here at Carefore De Labe, we decided this would be the perfect place to do our follow up experiment to the tyre width test over cobbles, which was a little bit inconclusive. So we’re gonna use this sector, for a tyre pressure test. And what a sector it is,
it’s one of the roughest. It is the third and final
of the five star sectors, in Parriere Bay, I think there are only four more sectors after this, only 15k through Rebay Velladrome. We’re not gonna use all of it, let’s face it, we’re a
little bit tired now, so we’re gonna use one
point, one kilometre. Starting down there, and heading in the direction of the race. And finishing just here on
the famous left hand corner. – The experiment is very simple, Matt and I both running Continental Grand Prix 4000 tyres, in
the size 28 millimetres, and we’re going to do three runs. Slightly regretting
what I wrote down to do, because we’re gonna do 100 PSI, and then we’re going to do 70, and then we’re gonna finish with 45 PSI. Now I think we know which
is going to be the best, which is going to be the most comfortable and probably the fastest as well. But what we want to try and find out, is just how much different it feels. – I certainly know that 100 PSI is going to feel very very different than 70 and 45, I can’t believe you’re making us ride 100 PSI, but we’ve got something else I believe. We’ve got a brand new bit of revolutionary technology to measure the vibrations of the Carefore De Labe. – We have.
– Take it away Dan. – As well as subjective
feeling after each run, we’re also using a very high tech, just out, vibration sensor. – Show us it then Dan. What’s it look like? – There we go, it’s a GCN
couerback water bottle, which I will fill to
the top before each run, I will then remove the top like that, and then we’ll see how much is left at the end of 1.1ks. – That is some seriously low fi tech. (upbeat music) – Run number one then, 100 PSI. And quite frankly, I’m frightened. I designed this little experiment, and I’m regretting it now, having ridden down that section of the Carefore De Labe. It’s so brutal, and, (taps on tyre) don’t know if you can hear that, it’s pinging, not gonna
be very forgiving at all. I’m glad we’re getting the worst one out of the way to start with. Okay. Three, two, one, go. Right moment of truth, oh too bad. (groans) Actually really bad. Oh my goodness, it’s got quite a crack already. Ah.=Three, two, one, here
we go, get my feet in. Blimey that’s bumpy. Well I lost my bottle straight away! (laughs) Well, two minutes and 23 seconds, really really quite horrible. I was all over the place. Especially this last sector, where it’s really really broken up and the cobbles are all
sorts of jagged angles. It’s actually a little bit sketchy, but really found it
hard to apply the power. ‘Cause the bike was just
skipping all over the place, so definitely not the PSI
I would choose, 100. – That was horrific. I’ve got pins and needles. Two minutes 39. Oh yeah. Not much left in that. (upbeat music) Run two then, slightly
more forgiving 70 PSI. (electronic music) Still quite bumpy. But a bit better. – Run number two, 70 PSI. So run number two, 70 PSI, far more comfortable,
still pretty jarring. I still wanna drop the pressure. Again, found it really really
hard to lay the power down. Easier on the smoother section, but on the bumpy section, I felt very difficult
to get the power down. But anyway, time of two 11, so that’s 12 seconds quicker
than my previous run. – 20 seconds quicker, that felt a lot better already. Taken 30 PSI out, not much difference on the high tech vibration sensor here. Probably got about an inch. Final run then, and I’ve decided to risk going down to 45 PSI on this one, which is three bar. Now hopefully I won’t pinch pump, so that is the risk, especially when you’re running
clinches like we are today. Bottle is filled up, three, two, one, go. (upbeat music) Oh now that, that is better. – Final run for me, 45 PSI. I’m hoping this is a bit more comfortable. Three, two, one. (upbeat music) Okay, two 01, so took
another 10 seconds off. So so much more comfortable, and I could actually lay a bit of power down as well. Whereas before, especially run number one, it was, I wouldn’t say
impossible to put power down, of course, but, bike went everywhere, but this time, yeah I was kind of gliding a little bit more. Still brutally bumpy, but it felt like I was
making some headway. So, yeah best by far. – I didn’t press it towards the end, quite as well, so that would have been about two 14 I think, but I didn’t press the button properly. Not much difference though on the high tech vibration sensor. Same for the three runs. Well where better to do the conclusion of our tyre pressure test than at the Rubay Velladrome itself. It has been quite interesting, because I wasn’t expecting it to be quite that bad with 100 PSI. It was so brutal, wasn’t it? If I ever say again,
“Let’s go do an experiment with 100 PSI on the tyres, over a cobble section
like that”, just shoot me. – I think I’ll just book annual leave, I certainly wouldn’t ride a 100 PSI through there again. But Dan you were riding
completely on fuel weren’t you? – Yep. – So what was the time differences between runs one two three then? – It was about 20 seconds,
just a little over. So the worst obviously
when we had 100 PSI in. But you can just pedal more can’t you? When you’ve got softer
tyres, and less pressure, you can pedal further across the cobbles, and therefore put more power down. Pretty simple. – Well for me, I was right. I was gonna and ride to around 250, sort of 280 watts, which is pretty modest. Started off quite quick on the kind of first section of cobbles, with 100 PSI, and from that point onwards, I just couldn’t get the power down. Same sort of perceived
effort for every ride, but for ride number one with 100 PSI, it was a quite modest average watt. Then when we took it down to 70, a lot better, I improved by 12 seconds, got a bit more power out. Then on the final run, with 45 PSI, I was the quickest by 20 seconds, and managed to put another
15, 20 watts down as well. So yeah, the more I
decreased the pressure, the more I was able to apply power, for the same perceived effort. – [Dan] Yeah. Well the vibration sensor
didn’t really give us much in the way of a conclusive
statistic, did it? – [Matt] No, I don’t know if that will really catch on, to
be honest with you Dan. – [Dan] But we can safely
say that softer tyres, are much more comfortable and faster over Parriere Bay. And you wonder then,
where Parriere Bay tech is going to go over the next few years. Because there are bikes out there now that are optimised to be
aero, with the bigger tyres. So perhaps, could we get to a point where we see a rise on 35C tyres, if they’re not an
aerodynamic disadvantage? – Or will we see the powers that be, the UCI, step in. – Yeah. – And put, because you know, it’s interesting but, will we see rides in the next few years riding all terrain grow bikes? – Could do, if they’re aero enough. I mean, you were quickest last year on a mountain bike, out
of three different bikes. – With my arms like this. – Yeah. Well all interesting stuff. I hope you’ve enjoyed it,
more than I have today. Right if you’d like to see that experiment that they did just 12 months
ago on three different bikes, mountain bikes, cycle
cross and road bikes, you can find that just down here. – Don’t forget to give
this video a thumbs up.

100 thoughts on “What’s The Fastest Tyre Pressure For Cycling On Cobbles?

  1. Are you going to try running lower pressures in your tyres? They should really help over any rough roads!

  2. can you safely go all the way down to 45psi on these tyres? methinks it's below the manufacturer's minimum pressure specification…

  3. Hey Guys. I love your network and your GCN Does Science videos, but I'm losing sleep over your poor experimental design. When you are doing multiple runs to test differences in a given variable, be it tyre pressure, tire width, cadence, standing vs sitting on a climb, etc., randomize the order! Flip a coin, roll a die, ask Siri for random numbers, whatever. By dictating the order you are confounding the effect of the test variable and time. I am a statistician. Feel free to reach out for help on your next experiment. Better that than I keep losing sleep.

  4. What handlebar is that on Matt's bike? It looks like it has a little rise, but I guess it's not a Specialized?

  5. Might want to consider using an smart phone app that can measure the acceleration forces. For example: https://itunes.apple.com/ca/app/accelerometer-data-pro/id308757921?mt=8 . – disclaimer I haven't used this myself.

  6. there is an iOS app called iDRIMS that measures roughness using acceleration, angular velocity and GPS to measure road roughness. Maybe next time do the experiment with the app in your back pocket.

  7. I've been using 23c tyres for many years around 95psi or so but I've finally bitten the bullet and gone for 25mm tyres. I'm a very light rider (54kgs) and my bike (Canyon Aeroad CF SLX 8.0 disc di2) weighs around 8kgs ith a saddle bag and a bottle….what sort of pressure should I be using? 85psi…80?? Seems lo, but I'm not used to wider tyres! Thanks. Great show, as ever,

  8. Big thumbs up down below for suffering on those 100psi all that pain , Dan we hope your bum will forgive you that idea.

  9. Nobody is going to do that race at 45 psi………After many years, I've begun to do my solo training with a 25mm tire in back (still use a 23mm in front) I usually run 95 psi front and back.

  10. How about doing a test of a set of different pedal systems (e.g Speedplay, Look, toe straps, MTB) and see how long it takes Matt to clip in?

  11. Great video, and made up for the gaps in the previous one on tyre width. I’ve “gone wide” in the last couple of months because I found that I didn’t sacrifice any speed (on my regular roads) using wider tyres at lower pressures. I now ride 32mm (inflated to 33.5mm) @60-65psi) on my cyclocross commuter, and 28mm (GP4KS II) on my road bike @65-70psi, which inflate to almost 31mm on my DT Swiss rims. Personally, I wouldn’t go below 60psi with a 28mm GP4K on normal roads, because it does start to feel squishy, particularly when out of the saddle.

    For people still “bragging” about running their 21-23mm tyres at >120psi etc. , I would seriously suggest experimenting with wider tyres, and doing a set of timed runs over the same roads. Unless you live somewhere with pristine smooth tarmac, you will probably find that wider tyres are actually slightly faster at significantly lower pressures – they don’t feel like it, though – you have to measure it because your mind will play tricks on you. After this, your backside with thank you and you’ll be a lot more comfortable 🙂

  12. Would be interesting to see the time differences across 23mm, 25mm and 28mm at three different pressures on both cobbles and normal tarmac. The ultimate test! I'd imagine 28s at low PSI for cobbles and 25s at medium PSI for the road…

  13. Get with the program already my roadie friends. Make the switch to road tubeless, run the widest possible rim/tire combo that fits your bike and significantly DROP THE PRESSURE. No pinch flats, actually no flats at all in nearly a year…and on the usual bumpy roads we all ride, you'll be faster and significantly less fatigued. It really is the future.

  14. Its just so stupid riding these superbikes over this fucking bad cobble roads. These bikes are not intended for this shitroads. Drive elswhere, dont be stupid!

  15. Great video, the kind of stuff that keeps me watching. Mat and Dan earned their keep on this one. I'm surprised that they didn't pinch flat at 45 PSI.

  16. Great video boys. I would love to see this test done on a 5+km climb AND descent with similar tyre pressure gaps, maybe 100, 80 & 60 on the same 25mm tyre. Would be great to see the results

  17. Should have used single-blind. That way there riders would not have known which pressure they were riding on and would have had to guess based on comfort level. There is more bias in the method they used for the video.

  18. I have definitely been running a little lower pressure than before thanks partly to stuff I've learned on GCN.

  19. Hey GCN if imma buy a road bike what kind of size of the tyre will be good? For rough road

  20. I wouldn’t run clinchers at 45 psi unless they were 32cm or larger. I think tubeless is the way to go for cobbles!

  21. Love the GCN humour! Why not have a GCN competition in Flandern? And do it on the special way only GCN can do? Thanks Dan and Matt for great video.

  22. Awesome, now we'll have 95+kg MAMILS trying to ride cobbles at 45 psi like 65kg riders. Do you guys work as salesman for wheel manufacturers? Pressure is so weight dependant, it's best not using general figures without referencing rider weight.

  23. Could you do a video discussing the recent hype over ceramic pullies and bottom brackets?? Claimed to save watts due to far less friction??

  24. Hi. Dan, what pressure would you normally run on those 28c tires? I guess that I am kinda similar weight to you

  25. Why is riding on cobblestone streets a thing? Is it because there are a lot of them in Europe and they can't be avoided?

  26. Large UK car/bike chain pumped me up to 135psi I have been using bike like that for a few days and its horrific, letting some out for sure.

  27. Would be interesting to see time results with the same three tire pressures from the velodrome. After all, it's not like the entire race is on cobbles.

  28. Whoa. Is Dan really slowing down that much??? It's looks like he started his runs before Matt but if you consider it takes Matt at least about 15 minutes to fully clip in each time, he still managed to finish ahead of Dan… each time… over a Km and a half???

  29. Thanks for sacrificing your expensive bikes on this test, no way I would ever risk my new Trek riding on that.

  30. "If we look like we've just done Paris Roubaix" he says almost totally clean… looks more like you've been riding some decent roads and have come across a few puddles!

  31. An Android phone provides a good relative measuring tool for this use. You can record and compare the vertical acceleration between the various runs, making 3 or more runs and normalizing the data. I've used this method when comparing various configurations for faster (and more comfortable) cross-country times between MTB (suspension and rigid) and cyclocross bikes.

  32. GCN's video "how to ride your bike on cobbleslike a pro" tells us the best position to hold the bars is drops or tops.
    So Matt rides on the hoods….

  33. Oh god, please don't give the UCI more ideas to hamper developments in the road bike market….
    As it is they already overregulate imo.

  34. I'm running 23mm front & 25mm tyres (first road bike!). What PSI recommendations for rough surfaces & maybe even uneven tarmac?

  35. Why not 90psi front/100psi rear, 60/70 then 40/50? I have started riding 35c tyres with 50/60psi. It feels like heaven and it is quite fast as well (believe it or not) They weigh 310g each so not too heavy.

  36. Just like the tyre width test, it should be run blind, as in the rider does not know the pressures, for an unbiased opinion. Let them guess the pressures.

  37. What is that thing protruding from Dan's stem… new front shock design? coat hanger? I've never seen anything like it before.

  38. 100PSI, are you for real! I'm 100kg and I wouldn't even run the rear at 100PSI on a decent surface, totally stupid starting point given the terrain AND your size, would be better off with 75/60/45, you should also have different pressures front and rear. The line you take also has an impact on the test as you cannot replicate it on each run. Also measuring the width of the tyres at each pressure and on the wheels as the 28mm can come up bigger/smaller deending on rim.

  39. I love the low tech vibration sensor. Also adding a cell phone taped to the handle bar and seat post would be able to record vibrations with the phone's accelerometer.

  40. Pehaps the most precise way for any tyre/aero/weight testing could be taking e-bike to show consistant power over the route.
    Surely not on cobbles, where shaking influences your body abilities, but there is totally different aspect.

  41. Good try but unfortunately the methodology is a trifle deficient. May I suggest that if you are running a test comparing tyre sizes, it is better to keep tyre casing tension (hoop stress) constant not PSI. As tyre sizes increase, their volumes increase more rapidly and tension increases accordingly at constant tyre pressures. For instance at 71 PSI: (1) a 23 mm tyre has a casing tension of about 5,630 Pa; (2) a 25 mm tyre has a casing tension of about 6,120 Pa; and (3) a 28 mm tyre has a casing tension of about 6,850 Pa. At equal PSI, the larger tires are disproportionately "harder". To have equal tyre casing tension of about 6850 Pa: (1) a 23 mm tyre requires a tyre pressure of about 86.5 PSI; (2) a 25 mm tyre requires a tyre pressure of about 79.5 PSI; and (3) a 28 mm tyre requires a tyre pressure of about 71 PSI. results between riders are also comparable provided the combined weight of the riders and bicycles are approximately the same. I am looking forward to seeing the results of this test.

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