Skinny higher pressure tires make a difference

EMGX

Active Member
I have a BH Rebel Gravel X Yamaha mid drive gravel bike that came with Schwalbe G-one 700 x 40c tires which have no flat protection and a max inflation pressure of 70psi. I wasted almost $100 on Tannus Armour inserts with tubes. Took them out because of what I felt was excessive additional rolling resistance. I initially thought there was something wrong with my Yamaha drive because performance degraded so much with the inserts. So I decided to try some thinner higher pressure tires that had flat protection and ended up with Continental Gatorskin 700x32c and a max inflation pressure of 102psi. Huge difference. Yesterday I took a first ride, 42 miles with ~1400 ft elevation gain. I often run with the assist off and at times thought I was still riding with assist on. With assist on it was almost as if I was riding in a full level higher than what I was in. The ride was still pretty good but definitely harsher over railroad tracks. I might have use for the Schwalbe gravel tires in the future but for now they are on the shelf along with the Tannus inserts.
 

Papadevo

New Member
Welcome to the world of using bicycle tires! They effect the feel and efficiency in ways that most people don’t expect. Have fun experimenting with the pressure ranges to adjust your ride feel. Maximum pressure isn’t always the most efficient. I’ve used the gator skins in 28 and find 70 psi to be about right for me. Good luck!
 

Sierratim

Well-Known Member
Schwalbe has a good article HERE that discusses the major aspects of tire rolling resistance. I particularly like this graph;
rollwiderstand_diagramm_2_en.jpg

In this comparison the wider tire has lower rolling resistance than the narrower tire, even with the narrower tire running at a higher pressure.

Schwalbe concludes that wider tires will have lower rolling resistance than narrower tires when run at the same pressures. When the pressures are different the rolling resistance becomes a function of pressure difference, tire tread, construction, and other factors. Depending on the combination of these factors narrower tires can obviously have lower resistance, but it is not a hard and fast rule, just sayin' 😎
 

EMGX

Active Member
Schwalbe has a good article HERE that discusses the major aspects of tire rolling resistance. I particularly like this graph;
View attachment 69294
In this comparison the wider tire has lower rolling resistance than the narrower tire, even with the narrower tire running at a higher pressure.

Schwalbe concludes that wider tires will have lower rolling resistance than narrower tires when run at the same pressures. When the pressures are different the rolling resistance becomes a function of pressure difference, tire tread, construction, and other factors. Depending on the combination of these factors narrower tires can obviously have lower resistance, but it is not a hard and fast rule, just sayin' 😎
I've seen their chart before but my experience with different sizes of even the same model schwalbe (brand I usually have bought) tire in different sizes has always been that thinner, higher pressure tires take less pedaling effort. Tannus makes similar claims about their solid airless tire vs same size regular pneumatic tires but I have read a few reviews indicating that Tannus tire have noticeable increased rolling resistance vs similar pneumatic tires.
 

Stefan Mikes

Well-Known Member
As the inflation pressure divided by inner area of the tyre means the force acting on the tyre wall. it is obvious the lower pressure in thicker tyres will produce the same force as higher pressure in skinnier ones. (Or, am I getting that wrong?) In other words, same air force exerted on the tyre walls means the same tyre stiffness, or the same rolling resistance.

What, however, about the fact thicker tyre has bigger contact area with the surface than the skinnier one? Is it not reflected in increased friction? (It is a question because I don't know the answer).

There also is another factor: The tyre tread. I can easily compare 1.75" Smart Sam (a slightly aggressive multi-terrain tyre) to 2" Electrak (slick but soft rubber tyre). Under the same road conditions, I'm achieving high speed on Electraks way easier than on Smart Sams! The difference is quite dramatic. (I use Smart Sams just because they allow me riding in light off-road while Electraks are road only tyres).
 

theemartymac

Active Member
I have a BH Rebel Gravel X Yamaha mid drive gravel bike that came with Schwalbe G-one 700 x 40c tires which have no flat protection and a max inflation pressure of 70psi. I wasted almost $100 on Tannus Armour inserts with tubes. Took them out because of what I felt was excessive additional rolling resistance. I initially thought there was something wrong with my Yamaha drive because performance degraded so much with the inserts. So I decided to try some thinner higher pressure tires that had flat protection and ended up with Continental Gatorskin 700x32c and a max inflation pressure of 102psi. Huge difference. Yesterday I took a first ride, 42 miles with ~1400 ft elevation gain. I often run with the assist off and at times thought I was still riding with assist on. With assist on it was almost as if I was riding in a full level higher than what I was in. The ride was still pretty good but definitely harsher over railroad tracks. I might have use for the Schwalbe gravel tires in the future but for now they are on the shelf along with the Tannus inserts.
I think your experience with the Tannis Armor is not truly related to air pressure, but excess deformation. A standard thin tire with no insert will have reasonably even air pressure on all sides, which means that there will be reasonably consistent stiffness on all sides. This will equate to a nice low rolling resistance as there will be minimal deformation. The armor inserts immediately create a think outer section, with the pressure acting on the sidewalls of the tire more than the tread. This is similar to weight distribution. If you stand on thin ice, your feet will poke through. But if you stand on thin ice with skis on, you won't. Your weight is the same, but the load is spread over a larger area. The armor is acting like a load distributor and preventing the air pressure in the tube from distributing evenly across the tread of the tire and maintaining that stiffness. That means the tread will be allowed to deform more, which results in increased rolling resistance. In fact Schwalbe even spins this as a pro on their site by saying you get a larger contact patch and better traction. No doubt you do, but that patch is because of increased deformation. To overcome this, you would have to jack up the air pressure until the tread was once again as stiff as the non-armored tire, but unfortunately the sidewalls are still limited to the same max pressure, and so you can't.

Now if you truly are comparing fat tires to skinny tires and no inserts, then apples to apples the fat tire will generally roll better at equal pressures. But since you don't usually get fat tires that allow 100+psi, you can't truly match the performance in practice. If you truly wanted to test the rolling resistance tire to tire, you would have to drop the 102 down to 70 and test that way. I bet you would find the tire suddenly feels like a wet noodle, and would snakebite on the first pothole. So you choice is skinnies with high pressure for low rolling resistance at the cost of rough handling and sketchy in the wet, or fatter with lower pressure and some comfort and traction. Any choice would be made sloppier by wrapping the tire in a pool noodle, which is really what the armor insert is functioning like.
 

Dallant

Well-Known Member
It’s not at all surprising that a thin, higher pressure tire is going to feel like less resistance. I suspect you'll notice more harshness than just on railroad tracks. The Schwalbes are a great all around tire for me and I generally run them at 40-50 psi though I’ve pondered other tires for pavement touring use and will consider the Continentals.
 

Sierratim

Well-Known Member
What, however, about the fact thicker tyre has bigger contact area with the surface than the skinnier one? Is it not reflected in increased friction? (It is a question because I don't know the answer).
If the tire pressures are the same for a wide vs narrow tire the contact areas would of course be the same; a 200lb bike + rider puts ~100lb load per tire. At 100psi each tire would have a contact area of 1 sq inch to support this load. The Schwalbe article discusses this as being related to deflection, the wider tire deflecting less for each rotation.

rollwiderstand_breit_schmal_s_en.jpg

Obviously for tires that are not at the same pressure or being of similar construction the situation is more complicated. Schwalbe explains this as a function of pressure difference, tire tread design, tire construction, and other factors.

Other sites also reference wider tires as becoming more popular in the pro races as data accumulates showing lower rolling resistance, all other variables being similar.

One of my sons is lead mech engineer for a bicycle components manufacturer. Among other products, they design and market bike tires. He confirms the same conclusions that Schwalbe and others have come to and the trend to wider tires in the pro circuits. He does stress that there are design variables between tires that impact rolling resistance so depending on specific choices, YRMV.
 

EMGX

Active Member
That is sort of academic since the max pressure on my 40c tires is 70psi while the max pressure on the 32c tires is 102psi so you couldn't run the 40c tires at a comparable pressure anyway. I sort of fell into that wider is better trap a few years ago with Schwalbe Big Apple tires on a regular bike and went up in size, the max pressure was lower on the larger tire and they required much more pedaling effort. From what I read pro circuit riders have only gone up a couple mm in tire width and down some in pressure but still run skinny tires at over 100psi so what they use and how they use them might not be very comparable with the average ebiker experience.
For me with my bike the trade off is the harsher ride of the thinner, higher pressure tires. On smooth roads there isn't much difference but there is at least one set of railroad tracks that I will stop and walk over instead of riding over with the thinner tires and a very broken up section of road that I will avoid or walk the bike on. Those spots are only somewhat less bad with the 40c tires and less (but still) bad with the 40c tires and Tannus Armour. The 32c Gaterskins are OK on hard packed fine gravel but not on larger loose gravel which I would try to avoid. A good thing is that both the G-one and Gatorskin tires are quick and easy to dismount and mount so I can switch tires before a ride if I prefer.
 

FlatSix911

Well-Known Member
If the tire pressures are the same for a wide vs narrow tire the contact areas would of course be the same; a 200lb bike + rider puts ~100lb load per tire. At 100psi each tire would have a contact area of 1 sq inch to support this load. The Schwalbe article discusses this as being related to deflection, the wider tire deflecting less for each rotation.
View attachment 69334
Obviously for tires that are not at the same pressure or being of similar construction the situation is more complicated. Schwalbe explains this as a function of pressure difference, tire tread design, tire construction, and other factors.

Other sites also reference wider tires as becoming more popular in the pro races as data accumulates showing lower rolling resistance, all other variables being similar.

One of my sons is lead mech engineer for a bicycle components manufacturer. Among other products, they design and market bike tires. He confirms the same conclusions that Schwalbe and others have come to and the trend to wider tires in the pro circuits. He does stress that there are design variables between tires that impact rolling resistance so depending on specific choices, YRMV.
Thanks for posting the links.
A lot of research has been done on this topic and even the pros are now riding wider tires at lower pressures for more efficiency.
Years ago I remember racing with 18-19mm tires at 120-140psi... glad those days are long gone. ;)

Inflation pressure versus rolling resistance
Lower tire pressure means fewer pounds of pressure on each square inch of the tire. Since the tire supports the same load at lower pressure, the contact patch will be larger. For example, Wheel Energy measured the footprint area of a 700 X 23mm tire inflated to 112 psi with 50kg of weight on it to be 75mm long and 15mm wide. The footprint of the same tire with the same weight on it, but inflated to 84 psi, became 82mm long and 14mm wide. The longer contact patch means that the tire deflection will be deeper, resulting in more internal friction and hysteresis within the tire’s layers. That makes the case that higher pressure reduces rolling resistance.

On rough surfaces, however, a tire at lower pressure is able to absorb more of the bumps than a tire at higher pressure, with less deflection of the bike and its rider. This is the same “sprung vs. un-sprung weight” argument that demonstrates why suspension makes a bicycle faster on rough terrain — it takes less energy to keep the bike rolling if only a small amount of weight is lifted (like a small section of the tire) than if the entire bike and rider is lifted by the bump.

If the bike were rolling on smooth glass, it’s clear that higher pressure would be faster. The question is, what is the ideal pressure for the surface you’ll be riding on?

For mountain bikes and cyclocross bikes, this is a lot more clear and shows why top riders tend to run quite low tire pressures on rough courses or where traction on sidehills is needed. On the road, there will be a point with every surface where, above a certain pressure, rolling resistance will increase.

1603311799304.png
 
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jim6b

Active Member
I find this actual test compelling. Riding on rollers it was observed that:

Tire width and Power needed to maintain speed:

28mm 90 psi 45 kph 299 W
28mm 70 psi 45 kph 327 W

40mm 70 psi 45 kph 449 W
40mm 40 psi 45 kph 516 W


[Summary at 6:06]

I find it compelling precisely because these are direct measurements unclouded by theorizing.
 
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EMGX

Active Member
I find this actual test compelling. Riding on rollers it was observed that:

Tire width and Power needed to maintain speed:

28mm 90 psi 45 kph 299 W
28mm 70 psi 45 kph 327 W

40mm 70 psi 45 kph 449 W
40mm 40 psi 45 kph 516 W


[Summary at 6:06]

I find it compelling precisely because these are direct measurements unclouded by theorizing.
No surprises. Simply riding with different tires (40mm at 70psi vs 32mm at 100psi in my case) tells the story. This confirms what felt obvious to me with my different tires and pressures. I don't doubt findings that racers of optimal weight riding 25mm road racing tires at 110psi instead of 23mm tires at 130psi find some advantage but that doesn't necessarily translate well to other situations as the video and numbers above attest.
 

EMGX

Active Member
It’s not at all surprising that a thin, higher pressure tire is going to feel like less resistance. I suspect you'll notice more harshness than just on railroad tracks. The Schwalbes are a great all around tire for me and I generally run them at 40-50 psi though I’ve pondered other tires for pavement touring use and will consider the Continentals.
I'm not saying that the continentals are better than other brand of similar tire but they have been transformative for this bike, for me. I have had 35c 100psi schwalbe marathon and specialized armadillo tires that have street tread on a regular bike. The smooth tread gaterskins seem to be faster and roll better on smooth roads but are harsher on worn asphalt and brutal on broken pavement. I got 32c only because 28c was out of stock when I ordered but I'm good with this size. I'm planning on doing some mountain rides that I hadn't considered with the G-One tires that came on the bike.

battery range is better and I've hit 25mph on flat roads (which is well beyond speed where assist cuts out) on roads where I would max out ~20 mph before.
 
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Manu

Active Member
The maximum or almost maximum pressure is the best performance, only in MTB competition it is chosen to lower the pressure of the wheels by having an extra grip on slopes both up and down but with the risk of undercutting the tire or tube.
The weight of the bike also influences the weight of the cyclist, that can lower or raise the l pressure.A 100 kilograms biker will need much more pressure than a 70 kilograms biker.
THE world of bike competition is different from the real world of the biker. In an EPIC in Morocco you see that the bikes sometimes go with light tires and a "mouse" for 800-kilometer routes through the desert, the weight takes away everything they can and they wear a puncture repairman.


Every competition is different.
 
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kmccune

Active Member
Schwalbe has a good article HERE that discusses the major aspects of tire rolling resistance. I particularly like this graph;
View attachment 69294
In this comparison the wider tire has lower rolling resistance than the narrower tire, even with the narrower tire running at a higher pressure.

Schwalbe concludes that wider tires will have lower rolling resistance than narrower tires when run at the same pressures. When the pressures are different the rolling resistance becomes a function of pressure difference, tire tread, construction, and other factors. Depending on the combination of these factors narrower tires can obviously have lower resistance, but it is not a hard and fast rule, just sayin' 😎
Ha an Lectric XP fpr a little while and the tires at max inflation made that thing rool like it was on steel or glass.
 

Taylor57

Well-Known Member
I keep the Espin Sport 27.5x1.95s at around 50 psi and they seem to roll fine. My son keeps the Lectric XP at around 27 and they also roll great. Mostly street and bikepaths for both. They rarely see dirt...
 

harryS

Well-Known Member
I just found this thread. I appreciate that Schwalbe chart, We put Big Apples on my wife's bike, and she consistently overtakes my bike with skinny Kenda Kwests coasting downhill. The chart confirms what we see in practice,
 

smorgasbord

Well-Known Member
This is all cool, nerdy, and informative stuff.

But, on our eBikes, we have big batteries and motors. We run 27.5x3" tires with Tannus Armour inserts and Turbolito tubes at 16-20 psi depending on conditions. We get a great ride and great traction and have a blast with less worries about flats. If our motors are working a bit harder to compensate for the inefficiencies in this setup, well, that's what they're for!
 
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Luto

Member
To the OP, it is complicated..... ;). But seriously, part depends upon how smooth the road is, tire width, road surface. In general there is an optimum pressure RANGE for each tire. Over all lower pressure, SUPPLE, side walls are showing to be more efficient.

I agree with @smorgasbord, at some point it becomes like "weight wennies". Mostly for fun, and very little practical difference in speed-efficiency, versus other factors, like how you position yourself, or that 35# of gear.