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Re: Big ol' tires!

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  • David Dannenberg
    This discussion echoes the discussion I have been having in my head and with some biking friends. I have 2.5 Hookworms on my Big Dummy. I keep them inflated
    Message 1 of 2 , Jan 6, 2013
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      This discussion echoes the discussion I have been having in my head and with some biking friends. I have 2.5" Hookworms on my Big Dummy. I keep them inflated to 65psi (the maximum) which on pavement gives lowest contact patch (about 3/4" wide) and what feels like very low rolling resistance. They take loads nicely, and although they can be a bit jarring when the front wheel encounters large rocks at glancing angles, they are wonderful over curbs, potholes, manhole covers etc. Like an automobile spring they become a bit more compliant when the bike is heavily loaded and feel safe and secure under loads. They provide good traction wet or dry. The sidewalls are very stiff. I have ridden several blocks on a completely flat tire. No fun, and slow, but marginally better than walking a full cargo bike

      That said, they are very heavy, and not particularly flat resistant. (I would rather not have to ride several blocks on a flat tire). I keep thinking I would like something lighter and more puncture proof in the same size and pressure range. 

      Options? well, I looked at everything Schwalbe makes.  The bigger sizes all run lower pressure. Also, the most puncture proof models like the Marathon Plus Tour with Smartguard are not made bigger than 2" (and are heavy). 

      I have friends who swear by Stans, though they do say that rim selection is important. I did run that slime for awhile. It failed completely on one tire and then I abandoned the system. Some people have told me that Stans is intended to be most effective at low pressure. That comports with my experience: a 2.5" tire at 65psi blows under load the slime just blows out the hole and the tire sidewall collapses (I think the bead may even have blown off of the rim!).  I have since been told that Stans should be fine at high PSI.

      Meantime I have heard of studies that show that, contrary to intuition, tires at lower pressure under many circumstances are actually faster than tires under high pressure. This is especially true on gravel or uneven surfaces where apparently the compliance of a soft tire is preferable to the energy wasting bounce and ricochet of a hard tire. I ride a combination of dirt road and pavement and still lean toward the high PSI….but perhaps I am wrong in that. The soft is more comfortable, but feels slower. 

      I have considered tire liners (more weight) and would buy Michelien's new Protek tube, but it is too small for a 2.5" tire. 

      So in all this confusion I have not made a decision. All I ask for is high pressure, large size, puncture resistance, excellent traction, light weight, and durability. Can't all be mutually exclusive can it? 

      By the way, in my experience all bike tires loose pressure, moreso the smaller higher pressure tires. On most of my bikes I check the tire inflation and add air before each ride. I check the pressure on BD only every several weeks or so and when I do check it has always lost some pressure.

      David Dannenberg


    • dr2chase@mac.com
      ... This Does Not Work with Big Apples. I tried once. The sidewalls are not stiff enough, and the tires fit loose (Schwalbe in general seem to be a little on
      Message 2 of 2 , Jan 6, 2013
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        On 2013-01-06, at 8:40 AM, David Dannenberg <ddannenberg@...> wrote:

        > This discussion echoes the discussion I have been having in my head and with some biking friends. I have 2.5" Hookworms on my Big Dummy.

        > I have ridden several blocks on a completely flat tire. No fun, and slow, but marginally better than walking a full cargo bike

        This Does Not Work with Big Apples. I tried once. The sidewalls are not stiff enough, and the tires fit loose (Schwalbe in general seem to be a little on the loose side, Nokian tends tight).

        > That said, they are very heavy, and not particularly flat resistant. (I would rather not have to ride several blocks on a flat tire). I keep thinking I would like something lighter and more puncture proof in the same size and pressure range.

        > Options? well, I looked at everything Schwalbe makes. The bigger sizes all run lower pressure. Also, the most puncture proof models like the Marathon Plus Tour with Smartguard are not made bigger than 2" (and are heavy).

        I think you should look at the 2.35" Big Apples. 60psi is not much lower than 65psi. I don't get many flats; last one was something like a stiff piece of 10-gauge wire that went in through one sidewall and out the other.

        > Meantime I have heard of studies that show that, contrary to intuition, tires at lower pressure under many circumstances are actually faster than tires under high pressure. This is especially true on gravel or uneven surfaces where apparently the compliance of a soft tire is preferable to the energy wasting bounce and ricochet of a hard tire. I ride a combination of dirt road and pavement and still lean toward the high PSI….but perhaps I am wrong in that. The soft is more comfortable, but feels slower.

        I compared 700c x narrow x 120psi, versus 26"x2.35" Big Apple (60psi), and the Big Apple had lower resistance. However, when the pressure is significantly down (below 40psi) I notice that it appears to be slower. At intermediate pressures I am not sure, but the front end is more prone to shimmy if I ride no-hands.

        What I have read in other places is that if equals are compared (meaning, equal sidewall tension, so 60psi in a 60mm tire, or 120psi in a 30mm tire, and tires otherwise the same) the fat tire will have lower rolling resistance. However, air resistance matters too, and the top edge of the tire front hits still air at double your road speed.

        David
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