# Thread: "a reduction of tire pressure and wider tires reduce rolling resistance."

1. ## "a reduction of tire pressure and wider tires reduce rolling resistance."

In mountain biking... "a reduction of tire pressure and wider tires reduce rolling resistance."
http://www.bernhansen.com/Tester/Dek...20schwalbe.pdf

2. I think that test is also in the tyre rolling resistance sticky up top. Personally I prefer the wider tyres and struggle if I run thin now

3. Originally Posted by anthonyi
In mountain biking... "a reduction of tire pressure and wider tires reduce rolling resistance."
http://www.bernhans en.com/Tester/ Dekktrykk, %20bredde% 20og%20knastens% 20innvirkning% 20-%20schwalbe. pdf
Amazing. That has been said and tested many times over the last 6-7 years. Even the Pro Road teams (scroll down a ways) are finally starting to believe it.

4. Originally Posted by jeffw-13
Thanks

5. interesting to see some science behind the wide and low psi is faster...

6. Very interesting test! The issue of extra weight for wider (and I assume also beefier UST) tires seems to be fairly insignificant...

"to accelerate a pair of tyres with an extra weight of 500g from 0-25kph (15.5mph) in 4 seconds requires an additional 4.2W power..."

I only wish they had included tube vs tubeless into the testing. From a wattage standpoint, what does introducing a tube into the equation do? I'm currently trying out a set of 2.1 UST RR's and have found them to be fast rollers indeed. But the 650g weight seems like a high penalty for an XC tire. I don't have a need to run ultra low PSI due to the conditions in my area. So what would be better?...

1) Standard 2.1" Evo RR at 550g (including lightweight tube) @ 25 PSI, or
2) Tubeless 2.1" Evo RR at 650g @ 25 PSI?

Logic seems to dictate the 1st option is better, but the tube's effect on rolling resistance is the variable. Also, I think the acceleration test was done on level ground. But in a climbing situation, (as most roadies know) you're actually accelerating with each pedal stroke. Hence, the "pulsing" effect while climbing. In this situation, a prolonged grueling climb can make that 4.2W much more significant, and make the issue of tire weight important. I know good spinning technique helps address this, but when I'm feeling gassed on a climb, all form goes out the window LOL.

7. when you compare some of the rolling resistance tests the German bike magazine test did it's 5 watts or less with UST tubeless.

Racing ralph 2.25 ust tubeless was 19.8 watts
Racing ralph 2.25 tubed was 22.3

Nobby Nic 2.4 tubed was 29.8
Nobby nic 2.25 ust tubeless was 25.8

They also did one 2 or 3 yrs earlier with a eclipse tubeless kit with the same results.

8. Accelerating on a hill is not what you are doing every pedalstroke, as the tyre is not going any faster. There is extra (and different) power required for hills, but it is not acceleration-related.

9. Originally Posted by derickt
Very interesting test! The issue of extra weight for wider (and I assume also beefier UST) tires seems to be fairly insignificant...

"to accelerate a pair of tyres with an extra weight of 500g from 0-25kph (15.5mph) in 4 seconds requires an additional 4.2W power..."
I'm glad you posted this, as I had seen similar test results some years ago but couldn't find them. Every single time I hear (or read) some anti-29er nut rant on about big wheels being harder to accelerate, it drives me crazy. Sure, they are 'harder' to accelerate, but by such an insignificant amount it's just a non-issue. Of course, when you tell the anti-29 crowd that, they want proof.

It's especially insignificant when you realize that we very rarely accelerate from 0-15 in 4 seconds, maybe only at the start line. When you factor in the reduced rolling resistance of the larger wheel, it gets even less significant. So, every other acceleration takes even less than 4 watts for the heavier wheel over the lighter wheel, to the point that worrying about it is like picking the fly poop out of the pepper.

10. Originally Posted by AlexRandall
Accelerating on a hill is not what you are doing every pedalstroke, as the tyre is not going any faster. There is extra (and different) power required for hills, but it is not acceleration-related.
Pedaling is a series of small accelerations. There is a slight deceleration in the pedal dead spot which is much greater on climbs than the flats.

A "fast" tire will decelerate less because of tread and casing efficiencies.

A lighter tire can be accelerated more easily but it also decelerates easily.

11. Guys the tire inflation pressure chart indicates that on the road the higher the tire pressure the less the rolling resistance.

This test also does not consider that higher pressures are normally run in thinner tires...

and on the road that results in less rolling resistance again.

Also if aerodynamics is also considered narrow tires again come out on top.

So if you are riding the road out to your trail head, you may want to consider narrower tires, to reduce both air and rolling resistance on the road... Especially with a solid or near solid center ridge ala Crossmark etc.

It is very clear that wider tires at lower pressures work much better on gravel and rougher terrain...

I would have preferred the testing to be completed a max tire inflation pressure, minimum tire inflation pressure, and the average of those two. But that is a small thing.

This test and my experience over the years are similar in results.

12. Originally Posted by gvs_nz
when you compare some of the rolling resistance tests the German bike magazine test did it's 5 watts or less with UST tubeless.

Racing ralph 2.25 ust tubeless was 19.8 watts
Racing ralph 2.25 tubed was 22.3

Nobby Nic 2.4 tubed was 29.8
Nobby nic 2.25 ust tubeless was 25.8

They also did one 2 or 3 yrs earlier with a eclipse tubeless kit with the same results.
Thanks for posting this. Interseting stuff. so the way I see it, tubeless vs tube is <5W gain in rolling efficiency. Light vs heavy tire is <5W gain in acceleration efficiency. So the advantages from picking a heavier UST tire over it's lighter tubed counterpart basically cancels each other out... Hmmm.

AlexRandall - I think we'll have to agree to disagree on this one. Climbing definitely involves acceleration physics. This is from the April '10 issue of Road Bike Action...

"As long as you are rolling along at a steady speed, wheel weight is not any more significant than the mass of your bike or body. The crow in the omelet, however, is that the top of your wheels travel at twice the speed of the bicycle - so the energy it takes to accelerate the wheels is compounded. Climbing wheels are built extra light because when the grade becomes steep, the bicycle slows and then accelerates between each pedal stroke. The extra energy that this pulsing motion eats up can be considerable, so reducing the mass of the wheels - especially the rims and tires - can save a lot more energy then removing considerably more mass from the bicycle or rider. As a side note: Watch the climbing stages of the next Tour de France and notice how smoothly the pros pedal. This is no accident. If you can learn to climb with a smooth circular cadence, you will eliminate wasted acceleration caused by pulsing, and can use that lost energy to reach the summit."

13. Originally Posted by jeffscott
Guys the tire inflation pressure chart indicates that on the road the higher the tire pressure the less the rolling resistance.
This is a mountain bike forum and mountain biking is typically done off road. Not surprisingly, the behavior is slightly different when analyzed in an application rarely seen and for which the tires were not designed. For road use, mountain bike tires are typically below what would even be considered for an on-road application. What the article says is that for off-road riding, fat, low-pressure tires offer lower rolling resistance (in addition to all the other benefits). Even if you ride to and from a trail on the road and don't change pressure, you're likely to save energy by using lower pressure because the savings of higher pressure on the road are minimal compared to the savings of lower pressure off-road.
Shiggy's link shows that on the road, with road tires, fatter, lower-pressure tires than what are typically used (even by pros) offer lower rolling resistance, and at least some pro-level teams are starting to recognize that.
Originally Posted by jeffscott
This test also does not consider that higher pressures are normally run in thinner tires...

and on the road that results in less rolling resistance again.
It absolutely does, because they did controlled testing across tire width as well as pressure. What can be taken from the article with respect to high pressure, narrow tires is that you're screwing yourself.
Originally Posted by jeffscott
Also if aerodynamics is also considered narrow tires again come out on top.

So if you are riding the road out to your trail head, you may want to consider narrower tires, to reduce both air and rolling resistance on the road... Especially with a solid or near solid center ridge ala Crossmark etc.
Priorities, man. I guess everyone draws their line in different places, but it seems ridiculous to add a bunch of work to the overall ride so you have a very slightly easier time on the road. i guess that might reverse itself if you were riding 30 miles road to and from a 3 mile trail, but who does that?
Originally Posted by jeffscott
It is very clear that wider tires at lower pressures work much better on gravel and rougher terrain...
That it is, and I think that's what matters to most people on this forum and who in general ride mountain bikes off-road. It also seems relevant to reiterate that lower-than-what-is-typical pressure and fatter-than-what-are-typical tires are also beneficial on a road bike.

14. Originally Posted by meltingfeather
This is a mountain bike forum and mountain biking is typically done off road. Not surprisingly, the behavior is slightly different when analyzed in an application rarely seen and for which the tires were not designed. For road use, mountain bike tires are typically below what would even be considered for an on-road application. What the article says is that for off-road riding, fat, low-pressure tires offer lower rolling resistance (in addition to all the other benefits). Even if you ride to and from a trail on the road and don't change pressure, you're likely to save energy by using lower pressure because the savings of higher pressure on the road are minimal compared to the savings of lower pressure off-road.
Shiggy's link shows that on the road, with road tires, fatter, lower-pressure tires than what are typically used (even by pros) offer lower rolling resistance, and at least some pro-level teams are starting to recognize that.

It absolutely does, because they did controlled testing across tire width as well as pressure. What can be taken from the article with respect to high pressure, narrow tires is that you're screwing yourself.

Priorities, man. I guess everyone draws their line in different places, but it seems ridiculous to add a bunch of work to the overall ride so you have a very slightly easier time on the road. i guess that might reverse itself if you were riding 30 miles road to and from a 3 mile trail, but who does that?

That it is, and I think that's what matters to most people on this forum and who in general ride mountain bikes off-road. It also seems relevant to reiterate that lower-than-what-is-typical pressure and fatter-than-what-are-typical tires are also beneficial on a road bike.

Lots of people ride to the trail head then ride the trail and ride home...

Lots ride over 20 km to the trail head...

I have ridden up to 50 km to the trail head...

Dead simple, pump up when you leave home, ride fast on the narrow solid center bead, then blow-off a little air for the trail....take a break and put a few strokes back in for the ride home...

Yeah that provides the least work, best ride....

15. Originally Posted by jeffscott
Lots of people ride to the trail head then ride the trail and ride home...

Lots ride over 20 km to the trail head...

I have ridden up to 50 km to the trail head...

Dead simple, pump up when you leave home, ride fast on the narrow solid center bead, then blow-off a little air for the trail....take a break and put a few strokes back in for the ride home...

Yeah that provides the least work, best ride....
True

16. ## point of diminishing return

So what is people's consensus on the point of deminishing return as far as how low can you go and why? I weigh 185-190 lbs and run my tires tubeless between 25-35 psi depending on which bike, tire width, riding conditions, and UST/2Bliss/standard tire. Any lower and I don't feel like I'm gaining any more traction and I start thinking things feel squirrely. As for how high of pressure, if I'm spinning out more than I think is reasonable then I drop some psi. I read about some guys running 20 psi who weigh 200 lbs and they say they occasionally bottom out the tire and I just wonder why? It's not like the lower you go the less the rolling resistance, right? It's just that a low pressure conforming tire rolls faster that a bouncing and deflecting firmly pumped up tire.

17. Originally Posted by ewarnerusa
So what is people's consensus on the point of deminishing return as far as how low can you go and why? I weigh 185-190 lbs and run my tires tubeless between 25-35 psi depending on which bike, tire width, riding conditions, and UST/2Bliss/standard tire. Any lower and I don't feel like I'm gaining any more traction and I start thinking things feel squirrely. As for how high of pressure, if I'm spinning out more than I think is reasonable then I drop some psi. I read about some guys running 20 psi who weigh 200 lbs and they say they occasionally bottom out the tire and I just wonder why? It's not like the lower you go the less the rolling resistance, right? It's just that a low pressure conforming tire rolls faster that a bouncing and deflecting firmly pumped up tire.
I'm the guy who's post you probably read and I think the point of diminishing returns is when you either feel too squirmy or bottom out the rim too much. I never felt too squirmy, but probably wouldn't go too much lower on a course like that.
I bottomed out my rim once, btw, and it was sort of a test to see how it went. If you look at page 7 of the paper that this thread is about it IS lower pressure = lower resistance (data point at <22 psi), with no clear indication of diminishing returns. FYI: 1 bar = 14.5 psi

18. Originally Posted by meltingfeather
I'm the guy who's post you probably read and I think the point of diminishing returns is when you either feel too squirmy or bottom out the rim too much. I never felt too squirmy, but probably wouldn't go too much lower on a course like that.
I bottomed out my rim once...
And I have said the same basic thing for years. You have to have the balance. Refer to the tire pressure sticky at the top of this forum.

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