There's lots of talk about wide tyres being faster than narrow tyres to I thought I'd do some timed roll-down testing to see if it's really the case. Follow me: Instagram: / davidjarthur Twitter: / davearthur
Nice video! Very easy to explain, at low speeds wider tyres are faster due to rolling resistance, at high speeds narrow tyres are faster due to aerodynamics, at high speed you won´t notice that rolling resistance especially when desending, just my opinion! At this moment i use a 28mm tyre, best of both worlds :)
@@mattball420 skinnier tire as a much longuer and skinnier contact patch, wide tires has short and wide contact patch. Skinnier tires has a greater surface of contact on the pavement at the same "comfort level"
@@mattball420 Because roads are not perfectly flat, the amount of force imparted by each bump is a major inefficiency. This is why, at some point, increasing tire pressure actually makes the system less efficient, because a softer (lower pressure) tire can hit those tiny bumps without imparting energy in the upward direction, conserving forward momentum. On a road that is not well maintained, one which has any cracks in the surface, 60psi is close to the ideal fastest pressure, and wider tires are suited to that psi range, while narrow tires are simply not.
I am always stoked about the amount of discussion the tire width introduces. Its quite simnple in my opinion: the more perfect your road is, and the shorter and faster your rides are, the narrower your tire can be. You will gett a more lively (lighter) ride, and better aerodynamics at higher speed with a 23-25mm tire on an average rim. the more "allround" and further away you want to go, the wider your tire has to get to be able to run lower pressures without bottoming out, and have higher comfort. 28-30mm, preferable tubeless on a wide rim is pretty much the optimum for most cyclists. it does not beat you up on longer rides, can cope with rough tarmac and some fine hardpacked gravel/forest roads, and will only be so marginaly heavier that you wont feel it after half an hour on your bike. i think much wider than 30-32mm on a road bike (focus on road bike) will not get you any benefits over this. a good 32mm tubeless tire at around 4bar is already very comfy and versatile. going wider only adds weight and drag. that said, if you want to have still more allround capabillity and tackle some gnarlier stuff, there are many good 35-50mm slicks out there that still roll very well and quick on a sportier gravel bike and allow you to pretty much go anywhere you want with only a bit of a penalty on the open road. the choice is really personal and up to what you want to do. there is no right or wrong, just get the right tool for the job. you wont put a formula 1 tire on an suv, and vice versa, wont you?
Personal experience I rode 25 and 28C the 25C tyres rolled better and accelerated better on smooth road. The 28C seemed a little more draggy but was definitely more comfortable on bumpy surfaces, and cobble stones. All tried at several different pressures. I feel it's six of one and a half dozen on the other myself but I know people will want to shoot me down in flames because they are so sure THEY are right and I don't know anything! So please don't bother to troll my comments..
Oddly enough the smoothness of the ride helps make the larger tires faster. Smaller tires can feel faster as the bumps etc give the impression of higher speed but those bumps (both the perceived and non perceived ones) actually cause a non trivial impact to speed even on fairly smooth surfaces. The larger tires ability to absorb more without changing its roll is part of what makes them faster, but that same smoothness will often make them feel slower. I think a lot of what the bicycle world does is by feel though so that’s why they’ve been popular. People also like to lurch from trend to trend overdoing it in the opposite direction. They also tend to follow the racing community instead of doing what’s optimal for the ways they are actually using a bike (an ahem example would be using thin aerodynamic tires that are super fast at 30mph because all of their imperfections are overridden by the fact that they have less air resistance, but are terrible for the speeds that riders operate at for 99% of their rides)
My go to tire for road is the Conti GP500 TL, and I recently switched from the already generous 28 (~65psi) to 32 (~50-55psi), I will never go back, lol! The "big hit" compliance is nice, but the best bit is over your standard road. I immediately noticed that the typical constant "road buzz" is essentially gone. By comparison, like ridng on glass. I always appreciate your great videos, David! Love to see little informative real world tests like this.
I got a screw in my 28 today. on your advice I ordered 2 conti gp5000 TL. My new Canyon Endurace came with tubeless set up wheels, but tube type tires. I'm hoping you steered me in the right direction! I'm eager to get the new set up going.
@slavelaboringkid7597 In cross, the ideal tyre pressure is where you kind of feel the rim every lap, but not too hard that it might snake bite. In most my riding over the decades I've stayed away from narrow. Just not comfortable, and I could hardly find a situation where it seemed to actually make me faster. Feeling more rattled is easily mistaken for "faster".
I remember when 18mm was fast, and 25 was unheard of. How much real science is happening vs marketing these days? For me, 25 up front and 28 in back seems to me the right balance (better aero up front, and less load)
I'm not a racer so adopted wider schwalbe pro one tubeless 3 years ago. The 28mm old version actually measures 30mm so when I bought the new model this year I have gone for the 30mm pair. I run these at 60 psi 4 bar which gives good grip on the corners and comfort on the c class roads in England. Whilst I have nothing to compare to I'm not going back to a hard ride produced by over inflation or poor quality tyres anytime soon. Enjoy the ride.
As you said, above certain speed aerodynamics come in to play. When going faster than 18 mph tire aerodynamics come into play, quite a lot because of its frontal area. Wider tires will probably weigh more, bigger tires, different tubes, and if done correctly wider rims. In my opinion, 25mm are best for fairly smooth road and when it comes to rough stuff you should use 28mm, as used by the pros in roubaix.
@@glennoc8585 sadly something like this happend to me, i was always running michelin dynamic sport 10$ tires nd they ad the perfect fit on my rim but i decided to get conti gp 4000 sii and now they blow out to about 27mm in my 25mm external rim. Really bothers me
@@larsborgman3443 Continental is famous for lying about their actual sizing. It's a marketing thing, because on the benchmarks of rolling resistance their products look better in comparison to competitors. Due to false sizing.
Haha! Hard to believe that 25mm is now considered narrow, when I can remember riding 18's and 20's, then moving to wide 23mm tires. On 28's now and loving it.
Lol, absolutely. I'm still looking for 22mm ones but hard to get them! Continental has some cool GrandPrix series but they aren't cheep. Benefit though, is high puncture protection!
Same here. I raced for a while on Conti 18's, but then settled oh 23's, mainly Michelins. During a 25+ year racing career I never raced on anything wider than that.
@@davidarthur I actually use 45-50 psi on 28mm tires (on 25mm internal width wheelset). Comfortable as heck but still handles like a dream on downhill curves. :)
Interesting video as always! I think you should also consider the tires themselves. The Giant Gavia Course 1 has 60 TPI, compared to the Gavia Fondo 0 with 170 TPI. The Fondo has also a (presumably) much better compound (RR-E instead of RR-S) and I think it will make a difference in the rolling resistance. I was riding the 30mm Specialized Espoir sport (60TPI /70a compound) and switched to same 30mm Roubaix Pro (120 TPI / GRIPTON) and could feel a huge difference in terms of rolling resistance. In any case, keep up the good work!
Also the larger tires are heavier which helps downhill but hurts uphill. He also gave the bike a kick in the beginning which might not have been consistent between trials. A flying start with an extract speed would have been better.
Hi David, thanks for doing the test it was a good effort but the results aren't quite what they appear. A. 32mm wheels/tyres accelerate slightly faster than 25mm tyres due to difference in torroid shape (91% vs 93% torroidal); B. 32mm wheels/tyres have higher kinetic energy than 25mm (even at the same speed) due to mass of around 150g for pair C. 32mm tyres have slightly higher aero drag than 25mm tire but only about 1watt at 24kph (fft.tips/tyre). You can plug this all into OMNI calculator and they suggest that 32mm will roll down a 25 metre drop 2.1kph faster than a 25mm tire (but they don’t control for air resistance difference, which I would say cut that in half) and this is not due to CRR. So basically the results aren't due to CRR it's mainly mass. Nice to get us thinking though! bw Alex from FFT
Right, the mass plays an important role. So in the test the difference in weight should be compensated by filling e.g. a water bottle accordingly to mostly eliminate that effect.
@@stefanwagener Yes, you could weight the lighter bike with say +150g in the water bottle vs an empty water bottle.....check my blog for more details search (cycling apps dot net)
Firstly, thanks for taking the time and effort to make this video and share your data. My questions would be: [1] Would weight have made a difference to the speed times as the extra mass of the 32mm tyre would have increased momentum and, therefore, the residual speed at the bottom? [2] As most people average a little more than the speeds recorded in your test over the course of a typical ride, would the poorer aerodynamics of the wider tyre come into play and caused more drag than the 25mm... thus losing speed... if your downhill roll speed had been a little faster? And [3], if (as on a typical ride), there is some ascending, would the extra weight of the 32mm tyres have conspired to slow things down overall when the rider is competing against gravity? In short, while your test is FAR better than a clinical wind tunnel test, I don't think it's as 'real world' as... well, the real world! There's probably no single solution to tyre width (and pressure) as every cycling scenario is different, but there's probably a 'safe bet' zone that puts you roughly in the ballpark of being on the 'right tyre for right now'. Personally, I think 25 - 28mm tyres offer that window, with pressures set to suit the rider's comfort on the given road surface they're rolling over.
Going downhill, added mass in the tyre overcomes its own rotational mass perfectly during acceleration. When at cruise speed, it's just added mass, thus faster. You can't make a wheel big and heavy enough to make it roll down slower.
Weight is often overrated. I am a recovering weight weenie. Say there is 100 grams extra in those 32mm tires. On a 90 kg rider+bike+kit combination that's 0.11%. Over a 17-18 second downhill, that's not going to move the needle, now is it? If the test was extended, flattening off and becoming a bit bumpt/gravely, that added rotational weight would help (a tiny bit) and of course the tire size would help even more. With standing gooey mud with hard bottom surface however...narrow might be better. But these tests are about understand real world more than bizarro world :-D
28's on my road bike and 32's on my fixed. Seems to work best for me - 28's still feel a bit more fleet of foot than 32's, but like the 32's on my fixed for comfort and stability, where outright pace is not as crucial. 28's are easily comfortable enough for me at the right psi. Changed from 25's years ago and never looked back
Hi David I've got 40mm on my gravel bike and 25mm on road bike the difference is marginal. I can go on any surface on gravel bike its brilliant. Thank you for your test.
I run 23 mm on the front wheel (45 mm deep rims) because of aerodynamics. At the rear wheel (88 mm deep rims) I run 30 or 32 mm because of comfort, and the air is so turbulent anyway around the rear wheel, so aero is not an issue there. Wider tires are faster in low speeds since deformation in the contact patch does not affect the side walls as much as in narrower tires. If side walls deforms, a lot of energy is lost. In the center of the tire there is rubber which springs back and gives back energy in the end of the contact area; like a spring.
I'm 6'2" 185lbs, I first tried 28mm rear and 25mm front. When I rode over new/ loose pavement pebbles would get caught between the tires and frame then burn the rubber down the center of tire. Happened to me twice. The front 25mm felt slow to turn in corners. So I moved the 25mm to rear and brought a 23mm for front. Even when the rear 25mm was pumped to max psi the tire always felt like it was on flat and swirly, the front was great. Then I got a 23mm for rear, to me the problem was solved. Later I tried 25's again, then went back to the 23's. I use the pirelli p-zero rated for 125psi, but aired to 105 front and 115 rear. I'm not looking down for flats anymore plus better all around performance. I don't notice any real comfort loss when aired to the appropriate psi. The only real advantage of wider tires to me is maybe braking.
Just moved from 28 to 30 (both tubeless) and even that makes quite a difference. I used to run the 28s at 60psi in front and 65psi in the back. When run at 60psi, the 30s are removing a lot more road buzz, it feels a bit weird when you are not used to it 🤪. Having a blast though and they are faster as well, which is not a bad thing. Might gradually reduce the pressure to 50-55 and see if that still feels grippy enough or if it's getting too mushy. Looking forward to the experiment!
Nice test! It'd be interesting to test if lowering the 25mm tyres to 65psi will increase the speed, or vice versa, if inflating the 32mm one to 80psi will reduce the speed.
Probably no for both questions. The area and the pressure force on the ground are the key differences. Increasing the 32 mm internal pressure would probably elevate the speed and vice versa.
You do realize how much speed road buzz saps...the fastest pressure for any given road surface is the highest pressure that isn't buzzy. Smooth with the wrong tires or a pressure far below the break point is slower, but harsh is never fastest. If all other factors are kept consistent, a harsh bike is always a slow bike.
I love that such a bike now takes 32mm! My TCr back in the day barely took 23s. I've done crosses on 30s, but also crits on 28mm cross tubes before 28s became acceptable. Decades too late for me. I was limited to Surly bikes to get extra tyre clearance for comfort, durability and control on rough or wet surfaces.
Where the biggest wide tyre advantage could come is cornering at speed. The difference between crashing and not crashing is huge. That said, in 60 years of cycling I have only sliden off on a corner on the road once, and that includes sometimes using 19 mm tyres at 120 psi.
I could be wrong. More than likely I am. But, you are testing out which tire is faster by coasting downhill. It stands to reason that the wider tire is going to have more weight and therefore more potential energy than the narrow tire. Now obviously rolling resistance is going to work against that potential energy but I feel like the only way to truly determine which wheel is faster is testing with a power meter. In my experience when it comes to narrow vs wide the fastest tire provides the most speed for the least amount of effort. Having started out with 38mm tires and eventually going down to 25mm tires, it is pretty clear the narrow tires require less effort than the wider tire. In other words I can ride farther on a narrow tire.
totally agree with your observation. A Conti 28mm on my road bike makes all the difference on a long ride compared to a 23mm for UK roads with a lot of potholes
This test is usefull, you cant put your favorite pressure, you need put the pressure for the same tire drop. The website rollingresistance is better, and dont exist any difference between wide or narrow
I recently did a 50 miler on 50mm tyres with my normal road group. I kept pace on flats, down-hills & short-sharp climbs, aerodynamics was not a problem; However, whenever the road pointed up for longer lengths of time- I got dropped. The mass of the larger tyres was only a problem when gravity overcame momentum.
Great vid! One problem I see is that coasting rolling resistance is only one part of real-world cycling. Most of the time you are pedalling. The pedalling action imparts a periodic force on the tyre, and there will be losses involved in counteracting this force. I suspect (but haven’t tested) that a wider, softer tyre will have different losses (hysteresis, air compression, etc) to that of a narrow hard (ie high pressure) tyre. Worth investigating?
There is also a difference between solo riding and racing. Who do I want fast tyres for my solo rides? Strava only, to be honest. In racing, roads are closed off and most of the time you're drafting someone else. Speeds are nor too much higher, but air drag ramps with the square (or cube) of speed. Most agree is the square, but a 100 hp car can go 200 kph, and a 400 hp car definitely can't go 400 kph. In a crit, the speed and easy I can take corners would be "critical", less acceleration to do. Crits killed me that way. Big guy, not a not of help from the slipstream of the shorties in front.
After pro racing on tubular tires, I switched to 26x2inch or 50mm tires for my recreational riding. That was over 30 years ago. Today I still ride a 26x2 tire on the road, though I certainly would not ride just any 26x2; tire construction is as important as air pressure and width....plus....as you so thoughtfully mentioned the more rougher the surface of road the more you will benefit from wide tires. I turned to bodybuilding after racing and gained weight, and now at 6 foot tall (2 meters) and 200 pounds (91kilos) with 13% body fat, those fat tires are wonderful for changing pressures and soaking up road vibration and shock. I ride a simple aluminum frame and steel fork with these tires it is a good and comfortable ride, a ride quality you will NEVER get on carbon and 25 to 35mm tires. The high profile of 26x2 allows air pressure changes I could never have done on 700cx25 or 28 tires. When racing at a weight of 168pounds (76kilos) (2 meter height) aggressive riding demanded the highest pressures or I would be pressing the rim into the pavement, flexing the sidewalls completely. So now I ride converted mountain bikes on the road fitted with aero-bars, bar ends and flat bars for the widest possible positions and one position with 100% relief on the hands. I own 4 road bikes all with different riding positions for a fresh feel on every ride. And still off-road ride as well using a 3 inch tire which is 1000x times better than those old 2 inch (50mm) tires. That extra inch in off-roading on soft trails is absolutely amazing, and for most my trails where I live are hard packed with baseball sized rocks...I will be going to 4 inch (100mm) tires for cancelling out the vibration of these rocky trails. Yes. wide is better....for recreational riding. Racing is a whole other story.
'm confused 2m is 6ft7inches if ur 6ft ur 1,83ish m... at 2m 76kg even 4 an athlete is quite borderline underweight. But gz livin that livestyle. 4 me, now an empty-nester I found my way bk to sports, never felt better... visiting St James did work a treat ;)
Continental tell me that larger tyres e.g. 28C vs 25C have greater puncture resistance as well, so another bonus. Plus as others have commented it would be great to have additional tests that include a range of tyre pressures as there are many of us who probably have our tyres pumped up higher than current advise (towards the maximum for those special rides). Thanks David for the excellent content in your videos.
I’ve been running 32mm for a few years. Slowly dropped from 60 to 45ish psi (200lb rider). My main gripe and reason for sticking higher pressure so long, was the handling when climbing out the saddle. Weight over the front wheel on a soft wide tyre makes it feel horrible and draggy.
My local roads are coarse chip and seal with a lot of expansion/contraction cracks that can be quite jarring. I wanted comfort over long rides without giving up too much rolling resistance. When the original 28mm's wore out, I replaced them with 32's - both running at pressures that gave 15% rim drop. The 32's definitely delivered the comfort, I didn't notice any slower rolling, and was pleasantly surprised at the noticeably better handling and traction. Wider was definitely better for me.
Interesting test but I cannot see how you can draw such a wide ranging conclusion from it. Surely this needs to be tested at pedalling speeds over a longer distance to really establish a clear benefit?
Also at faster speeds, like 35km/h+ for long distance. I think the 25mm are going to be faster. Also it heavily depends on the (inner)width of the rim and how well the tire fits to that rim.
There were 2 Parameters. Width and Pressure. Instead of arbitrary comfort pressures I would have chosen max allowable pressure or a percentage thereof for both tyres. Also, does rolling resistance at 40kmh still offset increased air resistance of wider tyres ? Last but not least I think sprinters want harder tyres as rocking the bike on softer tyres seems slower.
Great video, as always, but I will say that even 32s aren’t particularly wide these days. I upgraded to 35s, and continue to set Strava PRs. I may try 38s, and at least a couple of he flagship endurance bikes will take bigger than that. Interesting to see how 38s or 42s do, assuming they are actual road tires and not gravel tires.
I think 32/35 is probably the sweet spot between speed and comfort. And tire weight increases exponentially after abt 38/40. But I can’t bear to switch out the 43s to try to go faster because the comfort lets me ride longer. I can still track relative speed increases to monitor my progress.
This would be marginal- the difference is maybe 100g and the weight of himself with the bike maybe 70kg. Actually, it would be more important if he had eaten or drunk differently before the rides or went to the toilet before rolling down with the narrower tires.
@@LordVilmore Yes, the momentum of the spinning wheels would be a very slight advantage for the lighter wheel/tire combo. Since he does not roll out until the rolling "stops by itself" (as GCN did in one of their tests), he kind of "charges" the flywheel at the start (where the heavier wheel absorbs more energy) and then at the end he destroys this energy by braking. Concerning my eating and toilet statement: he did the tests several times, which should take care of this source of error.
Thank you for this practical testing, please consider coasting into your course at at approx 15mph, so that the aero factors are similar to your cruising speeds
This makes sense as when you consider the part of the tire that is touching the road: it’s footprint, is a small eclipse. Smaller on a larger tire as it has a larger circumference compared to a narrower tire.
my 23Cs are laughing hysterically at me, for those tests. With 2 pairs of new 23C spares, it'll be a loooong-time till I switch. A few seconds means nothing, and the $$$ stays in my pocket. hmmm...maybe the smooth roads here in my SW FL routes make all the difference? good testing & video, though! tanx!
Thanks David - been waiting for this one as you know from earlier comments. Another factor that can come into play is the the width of tyre compared to rim to reduce the negative lightbulb profile effect on the aerodynamics which you will hopefully cover in a future video. Importantly to me a big factor in favour of wide tyres is reducing the fatigue on the human body absorbing vibration so you are in better physical shape to pedal harder on a longer ride.
Bear in mind not all tyres are created equal and will roll differently. In my testing, I let the bike roll to a stop and there was little more than a single push on the pedal between slowest and fastest within a tyre pressure range of 55-95 psi. My choice of tyres comes down to comfort, grip, size. In that order. If they're available in my LBS that is.
Always enjoy your videos David. However, as I listen to your comments, I can't help but scratch my head. What you are basically saying in this test is the wider tires are faster at SLOWER speeds. Isn't that a bit contradictory? Who wants to go faster at SLOWER speeds? If speed is your goal, then you want to go faster at FASTER speeds. Seems like this is a bit academic with no real world relevance. as you correctly point out, at faster speeds, aerodynamics is far more important than rolling resistance. Narrower tires are always more aerodynamically efficient than wider tires. Yes, as you say, the rim width plays an important roll in the overall aerodynamics of the wheel/tire system and modern rims being wider, help to improve the aerodynamics of wider tires. BUT, this does not make them more aero than a narrower tire mounted to a proper rim width. I run 23mm tires on a rim with external width of 25mm, which has been shown in wind tunnel tests to be the aero sweet spot. I also find this to be true in my own testing. A 32mm tire mounted to a rim width of 33-34mm would achieve the best areo performance for that tire but it would still not be as aero as the 23mm tire on a 25mm rim. The best thing that can be said about wider tires is that they are more comfortable. But for me, even that is a bit subjective. I find that wider tires make me feel like I'm riding on marshmellows. It dampens the road feel but to me, on a racing bike, that is a drawback, not an enhancement. By reducing road feel, I am less confident and thus less comfortable.
@Radek Jean Ballard is an aerodynamicist and engineer. Here is what he has to say. "However, aerodynamics is just one part of the equation: tyres also have to exhibit low rolling resistance and wider tyres roll better. With this is mind, is there a point where aerodynamics becomes more of a factor in a tyre’s performance than rolling resistance? Ballard has combined rolling resistance measurements on rolling roads with the wind tunnel and explains: “We see this point to be roughly at around 30-35kph. This is only important for the front wheel. For this reason, for time trial and triathlon, we recommend a 23mm tyre on the front and a 25mm tyre on the rear.” Clearly, tire and rim width have a significant enough impact on aerodymanics to recommend narrower tires for tire trialing. Way more than .0000001 seconds per Kph. You should know what you are talking about before you comment.
To get a 1 second improvement in time at a speed of about 25 km/h, the coefficient of rolling resistance assuming the baseline is 0.005 would have to be reduced to 0.0044. The power savings amounts to about 1.4 watts for the same speed around 25 km/hr. Since there are more factors such as aerodynamics which I also considered in my back to back calculations, this 1.4 watt savings is offset by the frontal area increase of the tyre (a miniscule delta of 0.0049 square meter from 25mm to 32mm) at speeds greater than 25 km/hr. The breakeven point is a speed of >68 km/hr - or racing speeds where the advantage vanishes because of the incremental frontal area increase. The assumptions in this comparison are a baseline CD*A = 0.509*0.63 and an air density of 1.226 kg/cubic meter, a CRR = 0.005, drivetrain efficiency of 0.98. Weight does not come into play since the comparison was done at zero gradient. Incidentally, the savings in power is wiped out if the rider weighs 1/2 kilo on a 3% grade traveling at 17 kph. The savings in power is small - almost insignificant - but the felt comfort of the larger tyre can be perceptibly significant when run at lower pressures.
@@janeztomazic5546 I think it has been shown that lower pressures (within reason) contribute to lower rolling resistance over imperfect surfaces. So it is likely that 100psi in the 25mm tires will make them worst. I think there was an article in the Silca blog on this.
@@phoebetan7519 not true www.bicyclerollingresistance.com/specials/grand-prix-5000-comparison, 25 at 100psi would have better rol res than 32 at 60psi, this propaganda is really starting to piss me off; this video was made with specific conclusion in mind and than parameters were made so that the conclusion would be met. Who the hell even rides 25 at 80psi.... Pros ride 23 front 25 back in TTs, and even on gravel the widest they go is 28 (Strade Bianche), all the rest is bullshit like this video. Now if you want comfort please go 50 why stop at 32 but please stop bullshiting us that wider is faster.
@@janeztomazic5546 bicyclerollingresistance uses a rotating steel drum, which while consistent, may not reflect real world conditions. In the real world, increasing tire pressure will reduce rolling resistance to a certain point, after which rolling resistance actually increases with tire pressure. See blog.silca.cc/part-4b-rolling-resistance-and-impedance If tire pressure reduces rolling resistance, why not have solid tires?
@@phoebetan7519 they use a non smooth drum but yes, thank you for this; anyway from what I see here the breaking point is over 100psi; so if he could do the test at 100psi for 25s if possible with the same tyres the result would be different. I use 23 front 25 back both at 100psi, I believe also based on your link that that is the optimal combo in terms of rol res and aero
I just did a ride that included a section in a park. I rounded a bend and was surprised to see a black bear about to cross the closed road. I stopped pedalling and the loud ratchet sound through a carbon frame caused the bear to stop, turn around and high-tail it back into the woods. Off subject ik, but my ride is on 32 mm conti 5000.
Great video, interesting content and compelling delivery. I skipped ahead to the results and conclusions after watching the intro. Some chapters on the timeline would help other viewers who might want to do this also.
DIY rolling resistance test and comparison is best conducted with a negligible aero factor, under a lowest possible and meaningful ride velocity. There are two scientifically correct methods to consider. (1) static roll threshold force. Test data will be taken just when the bike begins to roll. (This is a test need a tire under test, bike, rider (or dead weight) and one or two helper to balance the bike at zero speed. A third person to pull the bike coupled to a digital scale.) (2) dynamic roll resistance: a powered vehicle tolling the rider and bike under test coupled by a bungee cord and a digital scale. Steady force data may be recorded at various speed intervals. (Make available the tow has an emergency release mechanism)
Force of gravity is constant and not reliant on weight. Think if you drop something light like a book and something heavy like a dumbbell at the same time. They will fall at the same rate of speed
I went from 25mm Rubino Pro's to 25/28 Specialized Roubaix Pro's - definitely more grippy and comfortable but im really only noticing that they roll much much better and smoother on the flats. if i had to put it into context Rubinos = good - Roubaix Pro's = literally floating on air. But when surfaces are rough and uneven the Roubaix just doesnt seem to roll that well... It could be that ive got too high a pressure. Im currently running R:75 and F:70 but i have ran 65/60 but that is just too low a pressure for the Roubaix. Ive ran 80/75 but i found the ride slightly jarring. Id like to experiment a little more but roads are currently wet and slushy with ice and snow. Climbing and acceleration also went out the window since the Roubaix's come in at 300g per tyre and they take quite a spin up to get up to the same speeds as i did with the Rubinos. I also love to randomly get out of the saddle and go for an all out sprint and the Roubaix's are a little hesitant to pick up speed where as the Rubinos are picking up speed almost instantly. I have a set of Roubaix's in 23/25 that will be going on the commuter soon so i'll be able to compare all three tyres a little further. I honestly think the 23/25 set will be pretty good.
I like the video and it illustrates how easily we can all measure the effectiveness of changes that we make to our setups. However, I would argue that these particular results are inaccurate for two reasons. Firstly, the times have been rounded to the nearest second. So 18s could really be 17.5s and 17s could really be 17.49s. Even with human error starting and starting the timer, an accuracy of 0.1s should be achievable. Secondly, just three experiments each isn't statistically significant, especially with such small differences. A good idea though, which can easily be improved upon.
Wider tire, more weight, increased speed due to more stored potential energy E=mgh. This energy came from the rider going uphill. Weight diff may have been enough to offset poorer aero of wide tire. Better to do closed course w power meter over long enough course to discern time difference. Ex aerospaced eng:)
Id love to see an out and back TT at higher speed/wattage (300 or more watts) to test the aero differences on that standard sized rim width with 25mm tire vs that new firecrest style wide rim with a 28 or 32mm tire. Really want to see if the rolling resistance gains of larger tires outweigh the potential aero losses at high speed... probably depends on the roughness of the surface though.
When I bought my bike it came with 20mm tyres, when I upgraded my local bike shop gave me 23mm tyres, didn't notice at the time, out on my first ride my average time, on a same route, was faster by 1.5mph, I have more faith in the wider tyre and attack the roads more, so was it the tyre or was it my trust in the tyre?
It'd be interesting to compare the power needed per distance, say 10km, by controlling the overall power, f.e. at a constant 200W tempo. This would incorporate the rotational mass difference, aerodynamics and fatigue into account too. Also, depending on the terrain, the vibration damping of thicker tires might influence the overall performance over long distances.
If a power meter can update agerage power precisely enough, it would indeed be interesting to see time needed for the 10 km course at 200 W average. And to equalize the test, staying as close to 200 W and average throughout. Rotational mass over a contant power effort is...nil. Unless you start from standstill. Rotational mass is mostly in the mind. I once went on a training ride with a friend, him on his road bike (accomplished bike marathoner), me on my "beach race" bike, 29.2.35 slicks. The rear tube I'd put 3.6 litres of water in. Yes, I noticed it slosh when changing speed by a lot. Once at speed, it was just riding as usual. I bet that over a 10 km ride at 200 W constant, that 3.6 litres of water (an American gallon or so?) would hardly be noticed in the measurement. Unless it was all a very steep uphill, then it would be worth around 3-4% at most. Weirdest about that test was perhaps how the tyre compliance felt. With so little space for air, it felt very stiff for the pressure on the gauge. A small bump would displace a huge amount of the air, and the water doesn't compress nearly as easily. I'm sure on a 10km gravel test (bring it oooooonnnn!) that water filled tire would have been...interesting. The water wasn't in pockets, so it could slosh freely. Would it help with a kind of flywheel effect...a little maybe. When taking sudden turns, braking, etc, I could feel the mass in precession if that's the correct term. that doesn't mean it takes eneergy necessarily, it could even help in some conditions. If it had been a tubeless setup with a large sponge donut between rim and tyre, filling the cavity completely...it would slosh less and be like a flywheel more. Maybe great on windy time trails, push through burst and keep stably on cross wind bursts?
@@Cloxxki the rotational weight has significant affect on acceleration and stopping performance, and the gyroscopic effect when turning. If suspension is involved, that becomes even more noticeable.
@@laurynasjagelo5075 What we SENSE and what the stopwatch can tell are two entirely different matters. I've done years of weightweenie engineering and racing. I just ended up faster with fatter tires and 3kg steel frames. The effort you sense as being expended to get rotating mass up to speed, is returned to you the moment you hit a hill or gust of headwind or need to back of a second. There's a rich tradition of using extra heavy wheels for time trials and record attempts. If a race is only a steep climb, then yes, weight matters. But you still need to factor in the rider which takes 90% of the perceived advantages away immediately. I'm 99kg. Bike and kit would make it 110kg (if I did the weight weenie thing). Saving 1.1 kg costs a fortune, and may well introduce reliability or funtional issues. That would be a 1% better time on a super steep climb, if all worked out well. The way I get out of bed any particular day makes more of a difference on final performance, though :)
@@Cloxxki I guess your argument depends greatly on the environment we're talking about, also whether is motor-assisted or not. On a flat track - I'd tend to agree, but not off-road. I've once done a test on heavy casing MTB tyres, and even 200g difference has resulted in statistically significant differences (based on comed k5 gas analysis computer)
For me, the biggest benefit of wide tires is on fast descents. A 120 psi 23C tire bounces down an imperfect road, losing traction. A 28+ low-pressure, tubeless tire maintains contact. With 28C on an ENVE AR 4.5 set of rims, I have great aerodynamics, reasonable weight, fast rolling, comfort, and traction. All boxes checked.
no they run 28 in the Flemish races. Maybe it is because other tests and theory says wider is not faster on a smooth road. I am quite surprised by his results actually.
Plus at the speeds the pros ride the more aero 25 makes a difference. For the average cyclist not so much. I’m not trying to win the tour so for me I’ll take the comfort of 28s over a few seconds
Faster should be looked at in terms of totality and not a single metric. If you ride 25's and rated PSI it might have the lowest rolling resistance but that only applies to very controlled conditions. When you factor in "real world" you also need to factor what the impact shocks of every little bump (both big and small) does to your overall performance. This is why you tend to see a trend towards lower pressure and wider tires..... Another example is the fact that I can't stand my bike after about 2 hours with 25's at higher pressure but can ride all day on 32's at lower pressure. Imagine being a pro and riding day after day after day. If wider tires at lower pressure greatly reduce daily fatigue for a multi day event...it might be worth a few rolling resistance watts for all the other benefits. But if you are doing a 1 day event that is 90 minutes in length...you might reactor your target goals and take that beating possibly.
Great video. However, it would be more scientific to test a single variable at a time rather than changing two variables (tyre size and pressure) and not knowing which one was responsible for the difference on speed.
I like this methodology as it’s closer to planned use conditions, although the pressure data is meaningful. It seems like there is a lot of good data for pressure with calculators from Silca, SRAM, HED, etc.
With a narrower tyre there is more kg per square centimetre pressure on the tyre, the wider tyres is more evenly distributed so will deform less. I wonder if that is what’s going on
More contact surface is better for accelerating, building speed and maintaining. Tire compound and thread obviiusly play a part too. Can't go too wide, drag will be more inherent and weight on climbs.
Agreed, most claims around bikes nowadays being faster which often are related to aero aspects and wider tyres at lower pressures are built around the assumption that everybody is riding a flat time trial (not a real world scenario as you suggested)
And I imagine that the benefits would be even better as speeds increase because of the lower pressure/wider tire’s ability to absorb inconsistencies in the surface impact forces generated at larger speeds.
Hi David Thank you for having the nerve to take up this question, you are about to sit up all night, answering people, because they are not ready ! But I have a question about the Giant tcr are you as amazed about it's comfort as when you started reviewing it? Thank you, and thank for your nice content and channel
Acceleration due to gravity is the same regardless off mass, see bowling ball feather experiments in a vacuum or the Apollo 15 feather and hammer on the moon
How do you explain the 18s with 23.9kph end speed to the 17s with 23.6kph. Initial starting speed must be different or the wind picked up. Also your testing distance is way too short, your *margin of error is too big* to conclude anything. It would be better if you picked a long downhill tunnel for example. And I haven't even talked-about using the same tires and making sure the bike weighs the same. And you should test multiple tire pressures to make sure it's the tire itself that's making the difference. I could go on and on.
You are correct about margin of error. We could have every one of us do a similar test and post our data into an document and then compare. I have a feeling that tyre quality matters more than size at such low speeds
Good video! More testing on the same topic would be interesting too, as per many of the comments. Up hill at fixed power. On flat at fixed power. At different speeds to understand when/if aero disadvantage offsets RR advantage. I’be sold my road bike rolling on 28’s and now riding on a 38c gravel bike. Best thing I have done!
Kjetil Korsveien Even when drafting, aero is still important and aero drag is still the largest force you have to overcome. Otherwise you could just ride a city bike in the peloton and have no negative consequences to your speed.
The advice has gone from 23 to 25 and 28. Now people are advising 30+, so how wide is optimal? The aerodynamics argument is always raised but there is little evidence or even theory given as to the circumstances where aerodynamics becomes the greater factor. I am assuming it becomes a greater factor at lower speeds as the tire becomes wider. I think advice like this is arguably as bad as the advice for narrow tyres was - because it is incomplete. Aerodynamics and weight are factors.
For not being scientific, your test is pretty close to being scientific! What I think of is the tyre choice. You not only chose different sizes, but also different tyres, that skews the results in my opinion. It might just be the type of tyre that is rolling faster.
Simple, ride the widest that fits during training for the extra weight and increased comfort. And use the most aerodynamic tire for your wheelset for races.
28 feels the fastest for the roads I ride on for my weight over 25 and 30. 30 feels a bit sluggish to pedal . 25 is too bumpy when I pump it up enough to support my weight of 220 lb.
That's a great simple test . I would have expected the higher psi pressure tyre to also be faster . Think I will give it a go myself . I ride mtb and have generally found the bigger wider tyres to be slower off road as it's more sand and mud to get through , but guess I will have to try and test it , head to the beach I guess ?! 👍🙂
I would suggest a longer section and to test the same model tire in two different widths. That 32mm tire looked like a touring tire and not just a wider version of the 25mm race tire. Construction could have been different. Still, glad to see that the wider tire was within the averages of the narrower one.
Incidentally I have a 2019 TCR shod with Hunt wheels (alloy) and 25mm Schwalbe Pro-One and it is super comfortable. I actually favor the TCR over my other bike which has 28 mm Schwalbe Pro-Ones also on Hunt wheels of about the same section depth because the other bike has a stiffer seat post (less exposed length). Both are tubeless.
What 25mm tyre was that? Looked to have tread on it (sloooow) and wasn’t the same model which makes it not a good test. You need to use the exact same tyre.
And is aero dynamics important in a tyre, especially in relation to the width of the wheel and maybe weight and if they were the same pressure. You did acknowledge this towards the end of your vid. Your tyre was clearly faster in your test, just it was not a good test, unless we all get to role down hills all the time. Not sure where you got the idea for this. Please don't make such sweeping statements from such a limited test.
