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  1. #51
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    Quote Originally Posted by Jay Strongbow View Post
    Faulty logic. Pressure can be lowered on good tires too. So harsher tires are harsher tires no matter how you slice it.
    True this, a stiff sidewall is a stiff sidewall no matter the air pressure. In fact the stiff sidewall under lower pressure will probably roll more sluggishly than a stiff sidewall with a higher pressure.

    A more supple tire with less pressure has a better chance of conforming around a flat hazard than a less supple tire with a higher pressure, which is a flat preventative in it's own right.

    Also the thinner thread pattern on the more supple tires have a better chance of deflecting the hazard away from the tire than a more prominent tread pattern, which many protected tires may have, which has the better chance of the debris lodging within the tread, eventually puncturing the tire.
    Too old to ride plastic

  2. #52
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    Quote Originally Posted by Lombard View Post
    We agree to disagree. That's what makes the world go round.

    The way I look at it, I am willing to pedal a little harder or go a little slower for the convenience of not having to stop and change flats. Changing a flat in colder weather or on an after work ride when you're racing to get home before dark really sucks.

    And the harsher ride of a less supple lower thread count tire can be countered with a little less pressure.
    Flatting is another subjective topic. I like the GP4000s and oddly enough have experienced significantly less flats with the 4000s than the gatorskins???

  3. #53
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    Flat protection is probably the last thing on my mind when choosing tires. I've been using gp4000IIs for 3 years without issues. Almost all the flats have been from hitting objects in the road which would have flatted any other tire as well. I tried some S Works tires last year but they felt slower and I ended up going back to the gp4000IIs. If you wait for the sales they have on the different websites the prices aren't that bad either.

  4. #54
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    I have been using Vredestein Fortezza Senso All Weather 25mm tires mounted to Campagnolo Bora C17 rims for over 2 years now. I have had exactly one puncture flat from a small piece of glass imbedded in the tread during that time period. So one flat in approximately 10,000 miles.
    I also have Continental GP4000S II 23mm tires mounted to Campagnolo Shamal clinchers that have experienced no puncture flats in several years.
    I use butyl tubes inflated to 90-100 psi and change my tires when they start to get squared off.
    The Continentals scored high for rolling resistance and the Vredesteins were one of the worst for rolling resistance. However I consider other factors such as handling and puncture resistance more important.


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  5. #55
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    Quote Originally Posted by Kerry Irons View Post
    You'll have to take this issue up with the entire scientific literature. It's the term that is used. Sorry.
    I was only aware of one guy ever really using the term and assumed he was the one that started it. Jan Heine at BQ.
    In the peer reviewed world of scientific literature, I don't think they would count his BQ publication.
    Here's my problem - I think road bike tires as the bike's suspension. More pressure = less suspension (harder ride) and less pressure = more suspension (softer ride). So it's odd to say lower pressure yields less rolling resistance due to suspension losses.

    But Jan Heine explains suspension losses another way, which I don't buy. To me it sounds like some weird unproven theory to explain the effect -
    "Looking through the literature and talking to experts like Jim Papadopoulos, we found a mechanism that could explain this: suspension losses caused by vibrations. As the tissues in the rider’s body rub against each other, friction turns energy into heat. And that energy must come from somewhere: It is taken from the forward momentum of the bike. Your body vibrates, and that slows down the bike. (The bike also vibrates, but it’s not as significant, since it’s mostly made from hard materials that don’t generate much friction.)"

    On the other hand, I gave my own explanation why lower pressure = lower resistance above. Which makes more sense to me, I'd call it "small bump lifting losses".

  6. #56
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    I had a sidewall failure on a GP 4000 IIs. It was a 10 mm long tear at the junction of the bead and the sidewall itself. I have no doubt that it was due to a manufacturing defect. It failed after about 2 weeks (200 miles) of riding.

    There were no burrs on the rim which might have caused this failure. The tire was replaced by Bike Tires Direct where I bought it.

    I have gone through 3 of them in the past two riding seasons. No issues with any others. The replacement for the one that failed is getting close to end of life with no repeat performance.

  7. #57
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    Quote Originally Posted by Z'mer View Post
    Here's my problem - I think road bike tires as the bike's suspension. More pressure = less suspension (harder ride) and less pressure = more suspension (softer ride). So it's odd to say lower pressure yields less rolling resistance due to suspension losses.
    It IS odd for a good reason. It's odd because you have it backwards. Lower pressure yields less rolling resistance due to LESS suspension losses.

    Is this what you meant to say?
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  8. #58
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    Given the tables in the article:





    Given the slopes of the lines, I have a very hard time understanding how there would be a pressure high enough where the overall energy loss would begin to increase again within the max tire pressure spec. Given that the bike doesn't significantly heat up, any "lift" loss would immediately be returned by gravity. The idea that the human body dissipates frictional heat due to this "lift" is impossible to disprove but seems incredibly unlikely as well. I agree that riding around on 130psi tires may well be uncomfortable, but lots of very light pros ride this pressure and seem to survive grueling 6 hour rides. Also modern components (especially carbon seatposts and bars) are much more compliant and make the ride smoother despite rock hard tires. I tend to ride 105-110psi because at lower pressures I hate the squirmy feel when pushing hard in or out of the saddle, plus I'm lazy and tend to pump up my tires every other, not every day. And of course I don't weigh 125 lbs.

    Also given fundamental aerodynamic principles. if you take the same shape and make it narrower (from the front anyways), it will always have a better aerodynamic profile. No matter what wheel manufacturers may say , somehow they aren't comparing apples to apples. Maybe other people experience lots of crosswinds, but God seems to not like me and blasts wind directly in my face.
    Last edited by DrSmile; 03-11-2017 at 06:08 AM.
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  9. #59
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    Quote Originally Posted by Kerry Irons View Post
    This cannot be emphasized enough. If I had a dollar for every time someone on this forum posted that "it feels faster" then I could keep myself in tires, chains, and cassettes with no expense. It is amazing that some folks never think that they can used a stopwatch to separate "feelings" from "reality."

    And yes, when pumping your tires hard "feels" faster then pumping them to a rational pressure will "feel" slower. But feelings are not the basis for making performance claims.
    Off topic but that's also why you see so many riders doing themselves a disservice by riding a ultra stiff twitchy carbon bike.
    Sharp handling and a super stiff frame definitely feels fast. But if you do rides of any distance the lack of comfort has the opposite effect.

  10. #60
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    Quote Originally Posted by Lombard View Post
    It IS odd for a good reason. It's odd because you have it backwards. Lower pressure yields less rolling resistance due to LESS suspension losses.

    Is this what you meant to say?
    No. If you have a positive net effect, you normally don't describe it using two negatives. If I make money in a stock trade, I don't say I had less financial losses on that trade. I describe it as a financial gain.

    So if lowering tire pressure = lower rolling resistance, I would call that a suspension gain.
    When designing 2 and 4 wheel vehicle suspensions, The term unsprung weight is used to describe the mass of the wheel/rim and other parts that move up and down over bumps. The goal is to make them weigh substantially less than the weight of the vehicle and passengers. So the vehicle rides flat and level and the suspension components absorb the bumps.
    Same thing happens with a supple bike tire at correct pressure over small road bumps - the minimal weight of the tire casing is accelerated up and down to absorb the rough road surface.

  11. #61
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    Quote Originally Posted by DrSmile View Post
    Given the tables in the article:
    ...I have a very hard time understanding how there would be a pressure high enough where the overall energy loss would begin to increase again within the max tire pressure spec.
    There are many problems with correlating tire rolling resistance on round drums with real world conditions on rough surfaces. And the author quoted by the OP did his real world testing comparing one tire against the other. He never tested the same tire at different pressures in the road tests.

    The best test for rolling resistance uses real world conditions, power meters, and average many runs. I found a test that did this for MTB tires. This confirms what many have been saying already - if you have super smooth roads, there is a rolling resistance benefit to higher pressures. As the surface gets more uneven, the benefit goes to lower pressure, to a point.
    Mountain Bike Tyre Rolling Resitance

    Their results - "reducing tyre pressures does not just leave rolling resistance more or less unaffected, as can be heard here and there, but actually reduces rolling resistance! This is true even on level paths of fine gravel, but the rougher the ground, the greater the effect,"


  12. #62
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    Quote Originally Posted by Z'mer View Post
    There are many problems with correlating tire rolling resistance on round drums with real world conditions on rough surfaces. And the author quoted by the OP did his real world testing comparing one tire against the other. He never tested the same tire at different pressures in the road tests.

    The best test for rolling resistance uses real world conditions, power meters, and average many runs. I found a test that did this for MTB tires. This confirms what many have been saying already - if you have super smooth roads, there is a rolling resistance benefit to higher pressures. As the surface gets more uneven, the benefit goes to lower pressure, to a point.

    Their results - "reducing tyre pressures does not just leave rolling resistance more or less unaffected, as can be heard here and there, but actually reduces rolling resistance! This is true even on level paths of fine gravel, but the rougher the ground, the greater the effect,"

    Well I am assuming that one rides on a road, not a meadow... Given the graph you show it seems even more likely that the benefit is pretty linear across the entire psi range, even a very low 30 psi seems to do better than 20, even on a very large MTB tire. Considering that the table stops at 60 psi and the OP's tables start at 70psi, there seems to be no inflection point where lower pressure would be faster on the road "test" surface, at least if you only consider rolling resistance, which is obviously a gross oversimplification.

    The argument of course is what exactly constitutes a "road surface" but my impression is that people think that potholes and cracks signify a rougher surface, which isn't really true. The tests done in labs usually greatly exaggerate the surface imperfections precisely to be able to find a measurable difference in the tires, when in reality no practical difference exists under real world conditions.
    Last edited by DrSmile; 03-11-2017 at 11:23 AM.
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  13. #63
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    Quote Originally Posted by Z'mer View Post
    No. If you have a positive net effect, you normally don't describe it using two negatives. If I make money in a stock trade, I don't say I had less financial losses on that trade. I describe it as a financial gain.

    So if lowering tire pressure = lower rolling resistance, I would call that a suspension gain.
    Bad analogy. Technically, you are right about the above. But I've never heard of anybody describing fewer suspension losses as suspension gains. Just like you never hear of anybody talking about hysteresis gains. And this is neither what you said, nor implied. Let me quote below your original post:

    Quote Originally Posted by Z'mer View Post
    More pressure = less suspension (harder ride) and less pressure = more suspension (softer ride). So it's odd to say lower pressure yields less rolling resistance due to suspension losses.
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  14. #64
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    I've always understood suspension lose to be the loses due to lose of traction when the tire is no longer on the road. The drum simulations just don't seem to replicate that.

  15. #65
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    Quote Originally Posted by cnardone View Post
    I've always understood suspension lose to be the loses due to lose of traction when the tire is no longer on the road. The drum simulations just don't seem to replicate that.
    Exactly. The diamond patterned drums simulate roads without imperfections at best. Throw in some imperfections, cracks, broken pavement, chip seal or other real world conditions and you have gone beyond what any of these tests have shown.
    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein

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  16. #66
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    Quote Originally Posted by Lombard View Post
    No, dude! Don't you know anything?? It's DISC BRAKES that make you faster!
    Also, Di2. Yeah. That's it. Unless the battery dies. Then, no.

  17. #67
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    Quote Originally Posted by Lombard View Post
    Exactly. The diamond patterned drums simulate roads without imperfections at best. Throw in some imperfections, cracks, broken pavement, chip seal or other real world conditions and you have gone beyond what any of these tests have shown.
    That thought occured to me as well. I also wonder about the way they are weighting the wheel and tire to the drum. It looks like it's hydraulic and pressed(pulled) down on the drum. A statically pressed weight rather than a hanging weight for example. This gives no other system wide suspension or reaction or transfer of energy to anything but the wheel and the tire. Only the tire and wheel can take absorb the changes in road surface. I wonder how this affects (if at all) compared to the real thing where energy is potentially transferred beyond the wheel. If they had a hanging weight type of test where there potentially might be more vertical movement of the wheel from the rougher surface. I wonder if that would affect the numbers. But I guess that is where the on road test does appear to track with the drum test though.

    Here's their site for more pics of the tire testing equipment: Independent Laboratory Wheel Energy Oy - Rolling Resistance Tests

  18. #68
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    Quote Originally Posted by cnardone View Post
    I've always understood suspension lose to be the loses due to lose of traction when the tire is no longer on the road. The drum simulations just don't seem to replicate that.
    No. Suspension losses are the energy that is dissipated in the body as road shocks are transmitted to the body. A "perfect" tire would be so compliant that it deformed around any road surface imperfections (no energy transmitted to the rider and therefore no waste) while having zero hysteresis losses due to flexing the casing and tread rubber. No such tire is possible but it explains why suspension losses are important. The tire does not need to lose contact with the road surface in order to transmit energy to the rider.

  19. #69
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    Quote Originally Posted by cnardone View Post
    I've always understood suspension lose to be the loses due to lose of traction when the tire is no longer on the road. The drum simulations just don't seem to replicate that.
    You're kinda thinking correctly. But the tire need not leave the ground. If you and the bike deflect upwards 1mm, you don't leave the ground. But it takes significant energy to move 150+lbs up 1mm. Now repeat thousands to tens of thousands of times.
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    Quote Originally Posted by tlg View Post
    You're kinda thinking correctly. But the tire need not leave the ground. If you and the bike deflect upwards 1mm, you don't leave the ground. But it takes significant energy to move 150+lbs up 1mm. Now repeat thousands to tens of thousands of times.
    This doesn't make any sense. Gravity returns the energy immediately, unless you keep raising the bike up (like going up a hill). The only loss would be due to aerodynamic losses in the vertical direction (possible?) and flex and resulting heat in the frame or the human. Neither one seems likely.
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  21. #71
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    Quote Originally Posted by DrSmile View Post
    This doesn't make any sense. Gravity returns the energy immediately
    Gravity returns the energy, but not in a forward motion. Thus it's energy wasted.
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  22. #72
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    Quote Originally Posted by DrSmile View Post
    This doesn't make any sense. Gravity returns the energy immediately, unless you keep raising the bike up (like going up a hill). The only loss would be due to aerodynamic losses in the vertical direction (possible?) and flex and resulting heat in the frame or the human. Neither one seems likely.
    So you saying/thinking rumble strips don't slow down a bike? Go try it.

  23. #73
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    Quote Originally Posted by DrSmile View Post
    This doesn't make any sense. Gravity returns the energy immediately, unless you keep raising the bike up (like going up a hill). The only loss would be due to aerodynamic losses in the vertical direction (possible?) and flex and resulting heat in the frame or the human. Neither one seems likely.
    Think pogo stick. Can burn plenty of energy going up and down with no forward movement.
    Too old to ride plastic

  24. #74
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    Quote Originally Posted by DrSmile View Post
    This doesn't make any sense. Gravity returns the energy immediately, unless you keep raising the bike up (like going up a hill). The only loss would be due to aerodynamic losses in the vertical direction (possible?) and flex and resulting heat in the frame or the human. Neither one seems likely.
    Look at their arms. Where's that coming from??

    Too old to ride plastic

  25. #75
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    Quote Originally Posted by velodog View Post
    Look at their arms. Where's that coming from??
    And.... do you think the energy moving their arms somehow gets returned into the bike as forward motion?
    If so, could I shake may arms to make me go faster?
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