Tire question?
 

Intuitively, it would seem that wider, lower pressure tires would present more resistance to peddling. Whereas, the opposite would - intuitively -
also seem to be true - that narrower, high pressure tires should provide less resistance to peddling. For now let's just disregard the tire groove
configuration.
Does this sound correct? I only ask because I am currently shopping for a hybrid type bike. Some of them have wider, lower pressure tires.
And I'm only interested in pavement, concrete trail riding.

Thanks for any comments,
Scubaquarius

Wider tires have been tested to have lower rolling resistance than skinnier versions of the same tire. It's related to rolling over the rough surface of a road. If the roads were glass smooth, like indoor tracks are, then the tires would likely be quite similar.

Lower rolling resistance at the same pressure. Equivalent rolling resistance at much lower pressures than the narrow tire. So wider is more comfortable on rough roads, but not slower.

However, it does depend on the tire construction. Thin, flexibile tread, like the smaller road bike tires, can efficiently flex over bumps. Extra thick, stiff tires that are extremely puncture resistant are a lot slower. And knobs can be very slow as they squirm when contacting the road.

Hybrids would tend toward the stiffer, puncture resistant end of the range. Those tires would be cheaper, have longer mileage, and fewer punctures. Good for casual riders.

Jan Heine at René Herse Cycles has done a ton of research on tires and has fairly well concluded that wider tires are not slower. I won't go deep into his thoughts as he can tell them better and has on his blog/journal but essentially for me lower pressure wider tires more easily rolls over anything instead of having to deflect and lose speed and with more comfort and confidence on the road I can go faster. However a lot of factors go into tires like tread, sidewall, rubber compounds...and that will all contribute or take away from your ride.

If you are looking for a better ride a nice tire with a supple sidewall and some extra width will certainly be a boon. The wider lower pressure tire will also help with flats as I eluded too above. A skinny tire is potentially faster on a smooth surface like say an indoor velodrome but in the real world the wider tire is going to perform better. Very few people after riding wider tires say "I want something a lot narrower" the only time I go narrow is when I cannot fit anything more in the bike which has happened a few times.

For me the perfect tire for road is in the 28-42mm range and ideally would be a nice soft and supple sidewall with a good rubber on top ideally with graphene probably in a nice chevron pattern or something non-obtrusive.

Very interesting, I guess that explains why I'm not an engineer :) .

Thanks, Scubaquarius

Thanks for the response and info.
Scubaquarius

Pedaling.

Alluded to

My opinion, which means little, is rolling resistance has little bearing on a hybrid with an upright riding position. The worst rolling resistance tire on a drop bar road bike will probably outperform the best on a hybrid.

That said, get a lightweight higher thread count quality folding tire and base the width on what you have now for the same or more comfort.

John

Not following your rationale here...lower rolling resistance always means less energy is needed to keep it rolling, so the benefits accrue regardless of bike type. As for outperforming, what do you mean by that? Tire rolling resistance performance has to do with the construction of the tire, not the bicycle it’s mounted to, so a tire with, say, a Crr of .0041 has that same Crr regardless of the bike type it’s rolling on (system weight and pressure being equal).

For casual riding, I'd choose comfort over efficiency, regardless of terrain. Higher volume = more comfort. A typical hybrid bike will probably feel and ride great with 35 - 42mm width tires. Stay within the manufacturer's psi recommendations, but experiment a little; five pounds of pressure more or less can have a noticeable effect.

I'm not sure I see that in reality, but then I'm a casual rider so most likely power constrained. With some testing I found very similar speeds between a 700x28c slick tyre on a drop bar road bike, to a 26x1.95" hybrid tyre on a flat bar hybrid bike (the road bike was about 5 seconds slower over a 2 mile lap). I certainly found the hybrid easier to ride with less concern about road surface.

I also found I could go faster on 700x40c than 700x28c because the road surface wasn't as problematic (there are some awful roads here that are bone shaking on 28mm tyres @ 100psi but not bad on 40mm tyres @ 60psi).

For hybrid commuters I'd probably go for comfort and durability.

There will be good tire choices for any width. For a hybrid, I would tend to go for wider tires. There won’t be much difference in efficiency for a good tire of any width, but the wider tire can be run at a lower pressure on rougher ground or a higher pressure (if you want) on smooth surfaces.

Also bear in mind that a bike’s geometry is designed around a particular wheel and tire size and the handling will change (at least a little) from that intended design if you change the tire size.

Otto

Tire construction is doubtless one key. For years the default was larger tires correlated with heavier, stiffer tires. That's a big reason we thought for years that wider tires were less energy efficient. I'll give Heine credit for getting some wider (started around 42 mm, IIRC), thinner, more flexible tires made and testing them. For completeness' sake, when Compass (now Rene Herse) tires hit the market at $70 each, I was happily riding $20 tires.

Another key is the surface you're riding on. There are a half dozen streets in my town I'd rather walk than ride because the etched concrete is so bad. Other than those abominations, 28-32 width tires are fine for me on paved roads. If you're going to ride dirt or gravel roads, the bigger the rocks, the wider the tire you'll want.

My point was wind resistance. If you are sitting upright with flat bars and another person with equal ability is in the drops, how much do you think your lower rolling resistance will help.

People agonize over the little things and ignore the major factor that will offset any gains.

John

TL/DR:
I have found that my bigger, cushier street tires are as fast or faster than narrower, higher-pressure tires they replaced...they just don't feel as fast.

Jan Heine talks about how the increased chatter between high pressure tires and the road feels like speed.

https://www.bikeforums.net/commuting...ig-bouncy.html
https://www.bikeforums.net/commuting...-part-two.html

The more that I learn about tiers, the more I find that I don't know. There are lots of factors and they all work together.

Rolling resistance: What is it really? Look at a tire on any loaded vehicle. There will always be a flat spot at the bottom. That flat spot moves around the tire as the vehicle rolls down the road. Now take a naked tire and try to push a flat spot into one part of the tread. That will require some amount of energy. On a bicycle that energy ultimately has to come from the rider. If everything else is equal, a tire with a thin supple sidewall will have lower rolling resistance than a tire that has stiff sidewalls. A tire that has a thick anti-puncture layer will have greater resistance than one that has a thin tread layer.

Now look at the shape of the flat spot on the bottom of the tire. The size of the flat spot will be approximately equal to the load divided by the tire's internal air pressure. A wider tire will have a short contact patch. A skinny tire at the same air pressure will have a long narrow tire patch. Remember the energy required to form a flat spot in the tire? If everything else is equal, at equal air pressure a wider tire will have lower rolling resistance than a narrow one. That means you can run a wider tire at lower, more comfortable, air pressure and enjoy the same rolling resistance or you can pump up a narrow tire harder to achieve the same rolling resistance.

All roads aren't silky smooth. Most people realize that a hard, high pressure tire will bounce more over every tiny little bump than a soft, lower pressure tire. That means that you are actually lifting the bike and rider upward over bumps that a softer tire would encapsulate. Guess where that energy comes from? On a bicycle, it ultimately has to come from the rider. That skittish feeling may feel faster subjectively, but it really takes more energy.

So why do racers use such skinny little tires? Rolling resistance isn't everything. At roughly 15 miles per hour on a flat road, air resistance surpasses all of the other factors that are holding you back combined. As you r speed increases beyond 15 MPH, the importance of air resistance becomes progressively more and more significant. Skinny little tires have less frontal area and consequently less air resistance than wide ones.

I assume there is a rubber compounding factor to rolling resistance but the only thing I know for sure about that is that carbon makes tires both black and wear longer. Look at little kids bikes - boy's bike tires, which are black, wear at least 3 times as long as little girl's bikes that have white tires.

Don’t forget that there are hills. Aerodynamics is scarcely a factor on steeper grades, so it’s hard work against gravity plus rolling friction. The difference of two slow tires could be as much 30 watts. I typically do 300-325 watts up our hills, and I would much rather put as much of that as possible into speed up a hill than dissipate it in slow tires. As an example, my 26x2.2 Race Kings are rated about 20W per tire, while there are MTB tires at more like 35W per tire.

Otto

It's not so simple as that. Air resistance is not just a function of frontal area, as turblence across the tire/rim interface and trailing edge of the rim can create a ton of drag. Being able to make light, wide, aero profile rims has changed the paradigm, and I'd bet the ranch that a 25c tire on a 22mm internal width rim with a 45mm deep profile has less drag than a 23c tire on a classic, 15mm internal width rim with a sub-20mm rim depth (e.g. the old Mavic Open Pro).

World Tour pro race teams usually run 25c these days (and wider on rough/cobbled segments), so they've come up in the past handful of years from 23s, but they're balancing weight and aero very carefully, so who knows if we'll see them on 30c in the future; I suppose it would depend on tire weight and rim weight for the width and depth needed to carry a 30c tire efficiently. Notably, Alaphilippe won TdF stage 2 last year on 26c S-Works Turbo rubber...on tubed, 33mm deep, 21mm internal clinchers at that, so yeah, width does not tell the whole story about aero.

Not to argue, but sooner or later you will be going downhill. And that upright position is a real killer.

MTB’s are a totally different animal as rolling resistance can be good or bad depending on the terrain. I’m sure there are those here who don’t want lower rolling resistance over wet slick surfaces.

My point is the rider position is a bigger detriment than a marginal tire gain. As I said a good quality, high thread count, lightweight folding tire is a good choice than splitting hairs on this or that particular tire “for a hybrid”.

John

Many people with training in science or engineering have studied rolling resistance. It is quite well understood. I suggest you seek out some of their explanations. The explanation you propose is mostly incorrect and only occasionally bumps up against what's true.

Keep in mind that a wider tire will have the exact same contact patch depending on which PSI you use.

So it mainly depends on the tread of the tire and how it works with your typical terrain conditions.

I generally use wide-ish tires for road riding, 32 or 35mm. On rougher surfaces and at slower speeds they are superior to narrow tires IMO.

Above a certain speed (someone above said 15mph) the aerodynamic resistance of the tires outweighs any difference in rolling resistance. When looking at the whole bike+rider+wheels system, at higher speeds, rolling resistance is a very small part of the energy equation.

This is the real point here. Aerodynamic drag accounts for the vast majority of cycling effort. Rolling resistance is rounding error in comparison. Within a given range of widths, pressures and tread patterns, some tires "feel fast" or "feel slow" but the actual difference in terms of watts expended to go a certain speed is pretty small.

I have no idea what "pretty small" means, but I do know that the difference in rolling resistance between tires can be 10 W or more (and of course, that's totally independent of what may be going on aerodynamically). I also know how hard I have to work to improve my power by 10 W.