Myosmith

Does anyone know of any data showing just how much tire width affects rolling resistance. I've read and been told that wider tires actually have lower rolling resistance but the articles, including one by Leonard Zinn https://velonews.competitor.com/2012/...rethren_209268, all state "at the same pressure" but the recommended pressure ranges are higher with narrower tires. What about rolling resistance with each width of tire inflated to its recommended pressure? Even if the rolling resistance is a wash doesn't the increased weight of the wider tire decrease performance?

I'm confused by the information I'm finding. So here is my question: Using the same wheel and the same make and model of tire, how much does rolling resistance change going from 23mm > 25mm > 28mm > 32mm if each is inflated to a pressure that results in the recommended 15% tire drop?

If anyone can answer this I would be most grateful as, being a clyde, narrow tires require very high inflation pressures to maintain that 15% tire drop. If I could go to a wider tire without a significant decrease in performance, it would be very beneficial.

Thanks

canyoneagle

There are several articles on the subject, but the bottom line (as I understand it) is that for a given pressure, wider tires actually have lower rolling resistance. Note the "for a given pressure" part, because (again, as I understand it) the pressure makes more of a difference than the width. 110 psi on a 23mm tire will feel as hard as 110 psi on a 28 or 32, so there is no real improvement in comfort if the pressure is maintained. However, wider tires allow you to take advantage of the larger air volume and sidewall height by allowing you to ride at lower pressure (say, 70 psi for a 28 or 32), providing a more comfy ride.
If you are on a road bike and can fit 32's, five them a go. In the 700x32 size, the Panaracer Pasela TG offers a very nice ride quality, but many others are out there, of course.

So the question the becomes "how much increased rolling resistance will 32's at 70psi give than 23's at 110 psi?". I don't have this answer, but I have ridden many tires and can say I prefer 60-70 psi to 110+ psi in non-racing use.

Here are some links from a variety of perspectives:
https://velonews.competitor.com/2012/...rethren_209268
https://janheine.wordpress.com/2012/0...ance-of-tires/
https://www.rouesartisanales.com/article-1503651.html
https://www.terrymorse.com/bike/rolres.html

To me, the data is less important than how the tire feels. I prefer a mix of comfort and performance. Alot depends on your use.

If you are commuting, the marginal loss in efficiency shouldn't be an issue vs. more pertinent factors of functionality and comfort (puncture resistance, etc)
If you are racing, consider tubular tires, which have a round profile (providing better cornering feel) and are less susceptible to pinching than clinchers.

Just my $.02, which is most certainly just one perspective.

cplager

Assuming that two tires are made out of the same materials and are at the same pressure, the wider tire will have less rolling resistance because the wider tire will have less deformity to get the same size contact patch as the thinner tire.

If wider tires have less pressure, then it is no longer obvious what happens. Assuming the tires have the same pressure, you are right, the wider tire will have more aerodynamic drag. Since aero drag is proportional to the square of speed and rolling resistance is proportional to speed, there is a speed at which the two tires should have the same total resistance. That speed depends tires, pressure, total weight, phase of the moon (o.k., not the last one)...

Cheers,
Charles

dsbrantjr

There are also factors beside rolling and air resistance; handling and comfort. I find narrow, rock-hard tires to be unpleasant and fatiguing to ride on; others may consider the experience to be manly or character-building. This article gives a good overview of all of these factors: https://www.bccclub.org/documents/Tireinflation.pdf

rjkfsm

For road riding, I run these 700x38 road slicks (https://tinyurl.com/cbg9bx2) on my hybrid. They have very little resistance compared to other 38's, so I think pressure has more to do with rolling resistance than width.

FBinNY 

As the data above show, wider tires can be more efficient, but there are other real world factors to consider besides width, pressure and payload.

On bumpy roads there's a horizontal component to every jolt. The energy lost is related to the tire diameter and height of the bump which together determine the strike angle and the total height and speed of the bike's rise.

This is where larger tires really shine. They can be ridden a bit softer, and can absorb the rise somewhat reducing the G-forces. This can't be done with narrow tires because there's not enough freeboard height and unless they're kept hard you'll dent rims.

Myosmith

Thanks for all the replies. Good info. I've got 23mm tires on my road bike right now, which were necessitated by the PITA narrow/tight rims that it used to have. I now have slightly wider more true to diameter rims and can easily mount any road tire I want. I never really liked the 23s though they did "feel" fast. I'm a clyde and had to run them at high pressure which made for a lot of road vibration and squirrely handling in corners or over any less than perfect surface. My touring bike with 25mm puncture resistant tires is slower but feels much more stable and comfortable, partially due to the tires and partially due to the bike weight and geometry. I'm planning to do some loaded touring this summer (only day tours, centuries and such last year) and was thinking of switching to 28s or 32s in the same tire and putting the 25s on my road bike, but don't want to turn my fast bike into a slug. I've been looking all over the internet and find all kinds of information but it is obviously a much more complex issue than I first realized. I read Zinn, Brown, Schwalbe, and more but can't find a definitive answer. Perhaps there isn't one. I did find this article which I thought was interesting as it looks not just at width and pressure, but also rim width and tire profile:

https://www.slowtwitch.com/Tech/Impli...idth_2803.html

The sad reality is that it isn't rolling resistance, tire width, rim shape, or even a few grams of extra tread that's holding me back. Its the extra 30-40 pounds I'm still carrying. A few salads will probably do more to increase my speed than any tire choice I could make.

Andrew R Stewart 

In real day to day life the rolling resistance of tires is pretty much a moot point. You use the tire which has the load capicity, durability, traction, and compatibility to your rims/bike that you need to surrive your ride. It's only when your pay check is on the line that this discussion has any merit.

This reminds me of a story. I had a shop years ago. there was a local group of riders (a club of sorts) that, of course, had it's pecking order. The strongest guys rode 700x18 tires at the inception of the group. They had heard that skinny tires were faster. Since they were pretty fit they did ride faster then most of the others (and faster then I did). Very soon most of the others were running 18s. As the Summer events started up my wife and I (on our tandem) would see them at the rides we liked to do. They would leave as a pack (I wouldn't say pace line as they weren't displined enough) from the start. At some point later we'd ride past some of them while one would be fixing a flat. Well they'd be in the shop every few weeks buying tubes in handfulls at a time, and the little 18 wide tubes were more expensive then the more common 23/25 ones. After a while I decided to thank them for their repeate business, asked them if they liked getting flats and if it bothered them that slower riders would pass them by when the didi flat. It took a little while but I did get them to move up to 23/25 wide tires. Of course they stopped getting any where near so many flats. They were faster with the wider tires as they weren't stopping while their buddy fixed their flat. So the moral is you're fastest not stopping. Andy.

FBinNY 

Yes, you won't find a definitive answer because there is none. Like just about every aspect of performance equipment, it isn't about an absolute right answer, but about balancing trade offs for optimal performance for specific conditions.

All things being equal, faster, stronger riders, will benefit more from the reduced air drag of narrower tires (within bounds), even if the rolling resistance is higher. At lower speeds, the opposite may be true. Then factor rider weight, riding style, pavement quality, cornering considerations.

Put all that stuff in a can, shake it up and pour out the answer of the day. And we haven't yet discussed the effects of tread compound on rolling resistance and wet traction.

The reality is that much of this is more a matter of fashion. Years ago tires started trending ever narrower, ultimately to 18mm. Now the pedulum is swinging the other way and 25mm is becoming more popular. I doubt that tires wider than that will ever be on high performance bikes, but it sure would be nice if bike companies at least opened up fork and chain stay clearances a bit, so heavier rider had the option to go tom 28 if they wanted to.

Six jours

Within tires of a particular construction type, I have not experienced a difference in speed between widths. IOW, if I have a 23mm, a 26mm, and a 28mm tire all of the same construction, I'm not any faster or slower with any of them, at least if the road is reasonably smooth. (A really rough road will favor a wider tire every time.)

A tire of heavy construction (Paselas, as an example) will pretty much always be slower than a tire of light "performance" construction regardless of width. For another example, 38mm Pacenti Pari-Motos are noticeably faster than the 25mm Paselas.

Of course, I'm not a time trialist. Most of my riding takes place at around 17 MPH. If you're going a lot faster, you should consider aerodynamics as well. I would never time trial on the Pari-Motos...

So considering the kind of riding I prefer (moderate, non-competitive speeds on a wide variety of road surfaces, and occasional moderate-to-fast club riding) wider tires make sense for me. Considering the kind of riding you do is your own problem.

Carbonfiberboy 

Every tire test ever done shows that higher pressure in the same tire reduces rolling resistance, regardless of the surface, smooth, bumpy, etc. I normally ride brevets on my single with 23c tires inflated to 140 lbs. They are very fast. One will be faster and more comfortable with a better, more shock absorbent frame and faster tires, rather than trying to smooth out the ride with slow, wide, low pressure tires.

Rolling resistance is determined by the volume of the material in the tire which is deflected and the amount of deflection. Energy is lost in the deflection of a substance like rubber. This energy is not recovered during the material's rebound. Thus a wide tire with a thin compliant body might have less material deflected than a narrow tire with a thick anti-flat belt and damage-resistant sidewalls. However, as many have discovered, a thin tire flats more frequently than a thick tire. Very compliant sidewalls are also less damage resistant.

The problem with presenting data for the OP's inspection is that AFAIK there are no formal published tests of tires of various widths, or even tires of the same width, in which each tire in inflated to the maximum sidewall inflation pressure. Leonard Zinn's contention is correct: wider tires will be faster than narrower tires if both tires are inflated to the same pressure. What he doesn't say is that a wider tire will almost always have a lower maximum inflation pressure and that the wider tire will ride rougher, not smoother, than a narrower tire inflated to the same pressure. You can't get something for nothing.

I am the ultimate clyde: I also ride a tandem with an all-up weight of about 350 lbs. We are fastest on 23c at 140 lbs., but I find them too fragile with that much weight sitting on them. Thus we are running 25c at 120 lbs. with only a small speed penalty, finding Continental 4000s to be the fastest and best holding tires of that width we have ridden. We are currently running 25c Schwalbe Ultremo DD, inflated to 120 lbs., as a wet weather tire and are very happy with the rolling resistance and handling of that tire, also.

I've done some informal tire testing on my rollers, trying different tires at differing pressures. Pretty much, the lighter the tire, the faster. The higher the pressure in a given tire, the faster on normal roads. Simple as that. There are some differences in tire construction that can make one tire faster than another of the same weight, but that's a smaller difference than plain tire weight.

My experience is that those who think wider tires are always faster simply haven't done any testing. Racers don't run wide tires. If they were really faster, they would.

I also don't subscribe to the 15% drop theory. I inflate to the maximum sidewall pressure. That's the fastest on normal road surfaces. Some say that the same tire, inflated to a lower pressure, will hold better when cornering. I have found the opposite to be the case. The biggest difference in cornering adhesion is caused by the tire's compound.

If you are riding Paris Roubaix and you weigh 120-140, you'll be fastest on the cobbles with 27c tubulars at 80-100 lbs. That won't work for clinchers, even at those body weights, a big reason they ride tubulars. For smooth surfaces, Zabriskie has used 160 lbs. in his tubulars on a smooth TT course.

Six jours

Volume 5, Number 1, page 26, Bicycle Quarterly: "Tubular tires are faster at lower pressures." The statement is accompanied by a graph demonstrating the test results.

The fastest tire on rollers would probably be a narrow steel strip. But on real roads, a narrow steel strip would be fairly slow. So the suspension of air-filled tires decreases rolling resistance over less-than-perfect surfaces. The question, then, is "How much air volume is ideal for a given surface?" There is no single answer.

Hmm...

Shimagnolo

Tell that to the pros: https://velonews.competitor.com/2012/...running_212925

FBinNY 

As I said there is no definitive answer. The goal is to understand the various causes and effects, and choose and use equipment best suited to you and where and how you ride.

The reality is that at decent speeds most of the total resistance comes from air drag, so marginal changes in tire drag have relatively small impact. In the scheme of things, one may decide to prioritize rough pavement handling and comfort, but that's their choice.

Carbonfiberboy 

Hmm. . . . for some reason you snipped the last sentence of the last paragraph you quoted, "For smooth surfaces, Zabriskie has used 160 lbs. in his tubulars on a smooth TT course." Perhaps because Zabriskie's experience was at variance with Jan the tire salesman's "test?" Get on your own rollers and try it yourself, if you don't believe me. Do a run at 70 lbs. and a run at 140 lbs. to make it simple. The difference is quite astonishing.

Six jours

I snipped to make it clear that in one sentence you say that pros don't use wide tires and then in another pointed out that pros do use wide tires.

As for tire performance on rollers, I just don't care. I haven't ridden a roller race in 25 years. In the real world, on the roads I actually ride, I can use wider tires with no performance penalty while enjoying increased comfort over narrower tires.

FBinNY 

Rollers aren't a good basis for tire rolling resistance tests. The curvature of the roller changes the rules because the contact patch isn't flat. But that's besides the point. There's no debate (or shouldn't be) whether the same tire has lower rolling resistance at higher pressure on flat roads.

But the rate of change in rolling resistance diminishes as the pressure goes up, so the incremental improvement may be more than offset by other factors (if they apply to the actual situation).

MichaelW

How would you test the total efficiency of a tyre in a real world situation?
A ramp roll test may be effective: find a ramp, roll down and see how far you roll on the flat on a windless day.
You would have to test all tyres on the same wheelset and adopt the same riding position.

rydabent

I think it has been proved that wider tires have less rolling resistance. The big thing that someone pointed out was the fact that narrow HP tires are very prone to snake bite flats. I have seen this happen time and time again. On rides the roadie on their narrow tires take off fast. Later in the ride I pass them on my wider tires while they are fixing their snake bite flats. Also in the worse cases they also suffer rim damage.

cplager

That's a start. The problem is that there are (at least) two (big) effects that are in play. Rolling resistance (which you can measure with your roll-down test) and air resistance (which depends very strongly on speed). Disentangling these effects is non-trivial.

canyoneagle

I think context will help - Myosmith - what type of riding do you do? Recreational? Racing? Commuting?
I personally think that for a clyde a wider tire would offer a better mix of comfort and performance. You've already established that higher pressure is not comfortable for you, and is pretty much the only way you can avoid pinch flats on a narrower tire.
I think a 28 or 32 at 70-80 psi would be a better choice for your needs (not knowing how you ride).

Carbon boy's advice seems to be from a pure racing perspective, and given that you feel that the higher pressure is not comfortable, I think the advice to run higher pressure is off the table (and is frankly racing-centric).

What type of bike are you riding?

Monster Pete

On anything other than a perfectly smooth road, give me wider tyres any day. Narrow tyres have to be run at ridiculous pressures to prevent pinch flats, and as such might as well be solid in terms of bump absorbing qualities. Given that most bikes have no suspension other than the tyres, running a wider tyre at a lower pressure gives you a better chance of not shaking yourself to pieces. Remember too that the more the bike rattles around over bumps, the more chance there is of a wheel lifting from the road- not something you want when you're going round a bend at speed.

cplager

There is also evidence that on less smooth roads, a higher pressure tire skips instead of rolling and this effectively increases rolling resistance.

bobn

I still can't see how putting more rubber on the road lowers the rolling resistance. It would seem to me that wider tread would create more friction than a skinny hardily touching the road tread, thus making it harder to keep in motion?

fietsbob

Something like a fat but high TPI casing, and very thin tread is more about the air volume, than
more rubber .. though adding more to the tread means you don't have to buy a new tire as soon.


Vintage Bike Quarterly tries to compare tire rolling resistance in controlled experiments.
its a subscription print publication, no on-line freebies.

Jan the publisher also imports high end Japanese tires.