http://www.bicyclerollingresistance.com/...corsa-g-tubular-2016

All of the tiers they test show the same trend

I don't think 120psi is high pressure. I have a friend that regularly rides at 160-180psi.

I think that rolling resistance is important, but not all important. As noted in the article, over 10mph, wind resistance becomes a bigger part of the equation.

While 25 or even 28mm tires are better for rolling resistance (with the larger air volume, they deflect less as they roll along, so that would be expected) I think however, that a narrower tire has better aerodynamics and that the net result is about 25mm tire on a suitably designed wheel, is the better choice for most people.

The caveat of course is that the wheel has to be matched to tire width. A skinny wheel for a 19-21mm tire, but with a 28mm tire installed, will be horrendous aerodynamically, but a wheel for a 28mm tire, with a 28mm tire installed will be much better.

At the end of the day, even aerodynamics isn't the most important thing! To finish fast, you have to get to the finish line in great shape. Even if a 19mm tire on a skinny rim is fastest when considering rolling resistance and aerodynamics, if the high pressure required to avoid flats will beat you up to such an extent that your legs will be toast (as will your will to live) and your legs won't put out any power to speak of. Going to a wider tire at lower pressure is probably faster in that case.

When choosing a tire, you need to weigh all the factors that affect you, on that course, on that day. If it's a hilly course with lower speeds uphill, then consider rolling resistance. If it's flat and constant speed, you will want to favour choosing an aero tire and wheel combo. If it's windy go with arero tires. If it's a really rough road, go with a wider tire at lower pressure to save your legs for the second half of the ride.

There is no one best tire, but there is a best tire for todays ride. Hell, for daily use I go with horrible RR and horrible aero puncture resistant tires because nothing is slower than standing on the road replacing an inner tube! (The roads here are covered with glass)

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TriDork

"Happiness is a myth. All you can hope for is to get laid once in a while, drunk once in a while and to eat chocolate every day"

Depends on how rough their is rough. Smooth surfaces sure.

I raced on I think it was 90 PSI with 25mm clinchers, rough road, it was over-presssurized.
Too much vibration you take a hit physically imo. Felt like I was bouncing on two high strung beach-balls. But I didn't stop to PSSST.

Tubies, 22 or 23mm I can ride 110 PSI all day long and it feels pretty good.

As with all bike stuff, I use "feel" as a guide.

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Training Tweets: https://twitter.com/Jagersport_com
FM Sports: http://fluidmotionsports.com

25ml of fluid weighs 50 grams?

Man, that is some heavy fluid. Twice the density of water.

Even the wheel energy rough drum is too smooth.
Made for material convenience not as anything approaching a real road.

Drum tests only test rolling resistance and do not include tyre drive losses for the rear tyre.

  
I was long skeptical of the "lower is better" line. Why? Because of literally hundreds of hours of road-testing different models of Mtb tires at different pressures over several years. I tested them on roads much rougher than any roady or triahtlete will ever see. Here's one of the smoother parts.




The results of this testing were very consistent: higher pressures were better. This lead me to ride (and win) the Mt. Ashland Hill Climb race several years running with Mtb tires inflated around 80psi.

So how do we resolve that with Tom & company's tests? You'll note that the bikeradar guy, like me, tested up a steep grade. I have speculated that, at low speeds up steep grades, the big torque from the rear wheel stretches the tire in a circular fashion. If you watch a low pressure Mtb rear tire as you go up a hill, you can actually see the ripples in the tire indicating this. So in addition to the normal hysteresis loss that we think of, you have a sort of torsional loss.

Some day, I'll redo these tests on both the hill and the flat ground. My suspicion is that the lower pressures will do much better on the flat than on the hill.

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My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

The trail in that picture apart from the occasional bump is probably smoother than a typical bitumen road.
I don't think that hills have anything to do with it apart from a more rearward weight bias will weight the rear tyre more.
What matters is the power being transmitted. 350watts on the flat is the same as 350watts up a hill apart from the weight shift unless you use dramatically different cadences.
But this is an area where I am really interested and surprised that not a single reply was made to my thread about it.
How much drive losses do various tyres have?
My bum measurometer says a 25mm tyre has far less drive losses even when run at a lower pressure than 23mm one.
Which is a bit counter intuitive as I would imagine a higher pressure would offer more sidewall support with less windup.
Maybe I am feeling losses due to squirm at the interface under power.

Take my word for it: the strech of the road in question is a hell of a lot bumpier than any paved road. Much of it is covered with 2-inch crushed rock.



I disagree. The same wattage on a slow moving wheel flexes the tire more at a given point. You can see this on a trainer. 300 watts when the wheel is moving 30mph won't cause the wheel to slip at a given press-on pressure; but if you try 300 watts at 5 mph, the wheel will slip like crazy.

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My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Several years ago, I noticed that if I didn't pump up my tires before a ride, I often got more Strava trophies and hit higher maximum speeds on descents. I played around with this for a while, sometimes letting my tires get down to the point where I worried I would get pinch flats. The sensation was that I was going slower, but the numbers were telling me I was going faster. When I finally got a power meter a few years ago, I spent an afternoon playing around with pressure, doing numerous runs on a nearby bike path (very smooth asphalt) and the road alongside it (noticeably rougher surface). After several hours of this, I've settled on 90-95psi for 23mm GP4000s on Flo 60s...

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"I'm thinking of a number between 1 and 10, and I don't know why!"

I find Josh Portner of Silca far more credible on tire pressure than this article, which wastes time with variable pressures on the rollers, an exercise that has no relevance to riding on pavement. He also wastes time with roll down tests only to conclude that they didn't provide useful data, something that any number of people could have told him before he started.

I think some people take the low pressure trend too far and I'm open to any credible new data one way or the other, but for now I'm using moderate pressures on my tires, on the road I use 90-105 psi depending on the wheel and tire width at 160 lb rider weight. As far as mountain biking, I don't compete off road and I use relatively low pressures because for me it significantly improves handling and comfort compared with wider pressures and with nice rubber they still seem to roll fine. YMMV.

Ah yes, so it is a torque thing not a power thing, I agree.
That is where I notice the 25mm vs 23mm drive thing the most, coming up the last 22% grade bit to my house.

Actually, because of the methods used, it doesn't add any additional info to the subject.

- The "rough rollers" test doesn't properly simulate the loss mechanism in the rider. All it's showing is that for that setup, a rougher surface just proportionally increases flexing, and losses, in the tires. It really just emphasizes that smooth rollers are good enough to rank tires.
- The road tests are on a climb, and most likely aren't done fast enough to "see" the breakpoint. Remember, the energy input into the tires is a function of both roughness AND speed.

As I said in other places today, I give it a "B" on effort, but a "C" on thoroughness, understanding, and conclusions :-/

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http://bikeblather.blogspot.com/

I think the test is a little misleading in that:

• thick butyl tubes are used, whereas latex would make the tube-type tyres look a lot more impressive
• the harmful effect of the butyl tubes is exaggerated by the heavy load, modest pressures, and small roller diameter
• the spread is narrow, i.e. all the tyres are pretty fast. From 2nd to 10th on the list is a spread of just a couple of watts, so inner tubes really matter to the ranking and the ranking itself is not as important as it might appear to some readers
  
• considering the narrow spread, the mounted tyre width significantly affects the results. This is ignored except for a cursory mention of mounted width in the tyre-by-tyre notes at the bottom
  
• for marketing reasons (I presume), Specialized labels the Turbo Cotton tyres as 24 mm and 26 mm when they’re more like typical 23 mm and 25 mm tyres. Since BikeRadar was testing nominally 25 mm tyres, they averaged the 24 mm and 26 mm Turbo Cotton results, which puts these tyres at another unfair disadvantage
• the Vittoria Corsa G+ is the wrong size but ranked anyway. Half the readers are probably too casual to pick up on this
• to the extent that road tests are useful, they’d be more useful at higher speed
• aerodynamics are ignored.

Many tests these days seem to have a sub-plot of pushing tubeless tyres, fat tyres, fat rims, and disc brakes by innocuously measuring the wrong thing. I don’t go in for conspiracy theories, but I’m amazed at the influence of trends on everyone including journalists.


Which other places, if you don’t mind sharing?

Jens, there are a lot of differences between your dirt road hill climb tests and a typical road, TT, or Tri situation. As I pointed out above, speed is a large factor in what level of energy is experienced by the system. I'm fairly certain that may be why Delaney didn't "see" any increases at higher pressures, along with the highest level being only 120psi (which is very close to the minimum Crr point in the test I did of 116psi). Then, there is also the tire size (and construction...you used tires with knobs, right?) and the hardness/softness of the running surface. Even hard-pack has more "give" than asphalt or concrete. Did your hill climb bike have a front suspension?

So...what I'm saying is: there appears to be a lot of significantly different variables between the 2 situations, such that I'd be hesitant to blanketly apply the results in one realm to another. It would be like saying disc brakes are great for MTBs and CX, so they MUST be the best possible solution for road/TT/Tri bikes ;-)

Sometimes you've just got to test out for the particular conditions :-)

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http://bikeblather.blogspot.com/

Oh, just in my personal echo chambers of FB and Twitter ;-)

Nice summary, BTW :-)

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http://bikeblather.blogspot.com/

By the way, rolling resistance is hugely important but better understood by most cyclists than just a few years ago. Big progress has been made there. I think it would be interesting to see bicycle tyre testing developing in some new directions:

First, wet grip. We really know nothing about wet grip except for the limited wisdom of the crowd. That wisdom suggests that some of the latest tyres are seriously compromising wet grip to reduce rolling resistance.

Wear life. Again, we only have anecdotes to go on.

Suspension losses in the cyclist. We need someone to take a stab at quantifying this for a variety of conditions. It would also be useful to generally know how it is affected by the cyclist’s body fat percentage, height and weight, fatigue level, etc. Should we grip the handlebars tightly or loosely to reduce it? Are cyclists with aero-bars disproportionately affected?

Some of these things may be less important to triathletes than cyclists generally.

if you discount the conclusions drawn regarding air pressures, do you think these conclusions fairly well represent what you and al and jarno have found, tire by tire? that is, that the 4000S II is a very good tire, but no longer the world beater that it was, and that the michelin power competition (and others) have slightly moved ahead? (tho not in price?)

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Dan Empfield
aka Slowman

I think that the conti's are still world beaters as from what I have read they seem to be better on coarser surfaces compared to similarly ranked tyres on smooth drums.
They also seem to respond to latex tubes better.
My gut feeling is that it is their rubber compound that still has the competition beat with both low losses and excellent adhesion along with impressive for the performance wear and cut resistance.

"He also wastes time with roll down tests only to conclude that they didn't provide useful data, something that any number of people could have told him before he started."

i don't (yet) stipulate to this. i have a protocol for a rolldown test that i intend to try. maybe i'll find the same thing as others have. but i won't know until i try it. i would simply stipulate to the drum tests were it not for josh's notes on how a rider aboard changes the calculus of the tire pressure tests.

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Dan Empfield
aka Slowman

"they seem to be better on coarser surfaces compared to similarly ranked tyres on smooth drums.
They also seem to respond to latex tubes better."

i haven't seen anything on either of these claims. is this just a sense you get, or has this been tested and i just missed it?

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Dan Empfield
aka Slowman

Other places than here, don't know which but I frequent many forums and get Tour mag as well quite actively seeking this sort of info.
I think that even in the test linked above they showed a bit of this behavior.
Again my untested theory is that the tread compound has very little losses so that deflections by higher coarseness surfaces slows it less than other brands.
Also fits in with the better response to latex tubes.

Love to see somebody target a test with maybe a Conti and a new Vittoria on differing surfaces, tubes and a reasonable spread of pressures.
Not too many tests to do if only two tyres involved.

But I do know that the 25mm Conti in general riding does seem to the gut feel meter quite impervious to road changes compared to a new 25mm Vittoria power tyre.
And I want to like the new Vittoria's as they run a little slimmer and they fit in my frame better than the Conti's.

Have you considered using Robert Chung's VE method instead of rolldown tests? It at least offers a diagnostic to give some sense as to whether a given run is junk or not. I've thought of doing VE tests to assess pressure changes but wasn't entirely convinced that I could get adequate granularity to make decisions beyond what I'm currently doing, a mix of informed decisionmaking based on accumulated reading over the years and personal observation of a comfort "breakpoint" at which tires seem to jump in harshness, which I can notice within a range of about +-5 psi or so, and which seems to correspond reasonably well with what Tom A. and others are reporting for RR increases.

"gut feel meter"

fine. but i don't want to hear anyone bad mouth my rolldown protocol if they're weighting the gut feel meter!

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Dan Empfield
aka Slowman

Jens, I highly respect your thoughts, opinions and findings but am having a very hard time wrapping my head around the concept of mtb tires pumped to 80 psi working in any situation, let alone off road. How wide were your tires and rims? What tires did you use? What size wheels - 29, 27.5 or 26? What sort of suspension - none, front or full? If you don't mind, please provide more info. Thanks. David K

Quick note about the Power Competition: it has less tread than the GP4000 SII and weaker sidewalls. Basically, it physically sits between the GP4000 SII and the GP TT. So they improved their compound vs what they used to have but they don't seem to have surpassed Conti's Black Chili