9 ms·

Interesting that they say nothing about consumption. I would expect them to be less fuel efficient, but having some number to go by would be nice.

bkanber 5y ago
As a general rule, tweels are worse for fuel consumption -- they are both heavier and have more rolling resistance. (Edit: weight automatically adds rolling resistance, but so does flexion, which tweels have more of. So tweels are a double-whammy for fuel economy.)
- kbenson 5y ago
  I wonder how that breakdown works for under inflated and overinflated tires, and what percentage of the nations tires are in that state at any moment? For a consumer product like this I think it's probably more important to compare the common case than the optimal case, because I know my tires often aren't in an optimal state, and as much as we could save as a nation by making sure tires were inflated correctly, we just don't, and I don't expect that to change meaningfully.
  - bkanber 5y ago
    Overinflated tires will always have better economy than underinflated, all other things being equal. My guess is the average vehicle owner could improve overall fuel economy by about 0.5-1.0% by making sure their tires are at the correct pressure.
    - kbenson 5y ago
      So, my thought when I said that was back when Obama mentioned keeping tires inflated correctly and getting tuneups to reduce oil consumption, and looking into that lead to this[1], which puts it at 0.6% on average, but up to 3% in specific cases. So I guess the question is how does 0.6% fuel economy loss on average for current tires compare to the loss in efficiency for using a Tweel, but according to some data from Michelin here[2], it looks like they're actually projecting them to be more efficient than current tires? I didn't read through the whole analysis, so I'm not sure, but that's what Table 7 looks like to me at a cursory glance and reading a few paragraphs in that section. 1: https://www.fueleconomy.gov/feg/maintain.jsp https://www.fueleconomy.gov/feg/maintain.jsp 2: https://manufacturing.gatech.edu/sites/default/files/uploads/pdf/2011-01-0093.pdf https://manufacturing.gatech.edu/sites/default/files/uploads...
      - bkanber 5y ago
        Funny -- I presented a paper at that very same conference! Mine was 2011-01-0755. The money shot is here. Note that '5.5 kg/ton' refers to the rolling resistance of the tire. > At this point the 5.5 kg/ton value is still only a design target, and this study serves mainly to confirm the environmental value of achieving that target. Essentially, this conclusion is tautological. "If there were a tweel that had better rolling resistance than the best pneumatic tire on the market, then it will have a better fuel economy and environmental impact." Obviously! I seriously doubt Michelin's tweel is anywhere close to that 5.5 kg/T mark. It's more likely something like 12 kg/T. The purpose of this particular paper is not to show that tweels are better environmentally, it is to show an analytical framework for calculating the full-lifecycle environmental impact of tweels vs tires. Sort of like a "here are the equations, plug in real numbers later" kind of thing.
        kbenson 5y ago
        Ah, nice to know, and thanks for giving a professional's assessment of what's being said. :)
        bkanber 5y ago
        :) Not a problem! Your experience hangs a lantern on one of the problems in academia. The authors of that paper did not intend to mislead -- this paper was published in 2011, likely written in 2010, only a handful of years after Michelin's unveiling of their gen 1 tweel design. To me, having been in the authors' position, I can easily tell what the true purpose of the paper actually was (the analytical procedure). But the authors had a secondary purpose driven by 'hype', almost, you could even call it click-bait: they wanted to make the tweel exciting so that other researchers would get interested in it and continue the work. One way to do that is by showing, from a materials perspective, that it is theoretically possible to design a tweel with a low rolling resistance, and given that, it's possible that tweels will be better for the environment over the full-lifecycle, including manufacturing and materials. And sure, this absolutely did/does deserve more research. However, the other issues with tweels, like NVH/comfort/etc, were 'out-of-scope' for that paper, and so they ignored those. Solving for those issues is what makes that 5.5 kg/T figure difficult/possibly impossible to attain. When these papers are confined to academia, it all works out, because most of the people who read your paper are other people who are writing papers, and they get it. But once these types of papers are picked up by the press/media/general populous, they can be very quickly misinterpreted! (To be clear, you didn't do anything wrong here, I'm just griping a bit about academia and pretending like I'm 'adding context' ;)
  - bluGill 5y ago
    TPMS has been law in the US since 2007. People might be driving around with under inflated tires, but there is a light on if they are.
    - bkanber 5y ago
      My cold tire pressure is supposed to be 33PSI, my TPMS doesn't alert until it's below 28PSI, so there is a significant delta still. The TREAD law does not specify when TPMS must alert, other than the tire being 'significantly underinflated'.
      - loeg 5y ago
        The NHTSA has determined that the requirement is that TPMS alerts for 25% underinflation across any combination of tires, or 30% underinflation in a single tire.[1] Originally they wanted 20-25%, but determined that cheap TPMS sensors were not good enough to meet that threshold and did not want to impose the cost of better sensors. [1]: https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/TPMSfinalrule.pdf https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/TPMSfinalr...
    - loeg 5y ago
      TPMS doesn't alert until tires are something like 25-30% under pressure, which is pretty severe.[1] [1]: https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/TPMSfinalrule.pdf https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/TPMSfinalr... (page 10)

bkanber 5y ago

As a general rule, tweels are worse for fuel consumption -- they are both heavier and have more rolling resistance. (Edit: weight automatically adds rolling resistance, but so does flexion, which tweels have more of. So tweels are a double-whammy for fuel economy.)

kbenson 5y ago
I wonder how that breakdown works for under inflated and overinflated tires, and what percentage of the nations tires are in that state at any moment? For a consumer product like this I think it's probably more important to compare the common case than the optimal case, because I know my tires often aren't in an optimal state, and as much as we could save as a nation by making sure tires were inflated correctly, we just don't, and I don't expect that to change meaningfully.
- bkanber 5y ago
  Overinflated tires will always have better economy than underinflated, all other things being equal. My guess is the average vehicle owner could improve overall fuel economy by about 0.5-1.0% by making sure their tires are at the correct pressure.
  - kbenson 5y ago
    So, my thought when I said that was back when Obama mentioned keeping tires inflated correctly and getting tuneups to reduce oil consumption, and looking into that lead to this[1], which puts it at 0.6% on average, but up to 3% in specific cases. So I guess the question is how does 0.6% fuel economy loss on average for current tires compare to the loss in efficiency for using a Tweel, but according to some data from Michelin here[2], it looks like they're actually projecting them to be more efficient than current tires? I didn't read through the whole analysis, so I'm not sure, but that's what Table 7 looks like to me at a cursory glance and reading a few paragraphs in that section. 1: https://www.fueleconomy.gov/feg/maintain.jsp https://www.fueleconomy.gov/feg/maintain.jsp 2: https://manufacturing.gatech.edu/sites/default/files/uploads/pdf/2011-01-0093.pdf https://manufacturing.gatech.edu/sites/default/files/uploads...
    - bkanber 5y ago
      Funny -- I presented a paper at that very same conference! Mine was 2011-01-0755. The money shot is here. Note that '5.5 kg/ton' refers to the rolling resistance of the tire. > At this point the 5.5 kg/ton value is still only a design target, and this study serves mainly to confirm the environmental value of achieving that target. Essentially, this conclusion is tautological. "If there were a tweel that had better rolling resistance than the best pneumatic tire on the market, then it will have a better fuel economy and environmental impact." Obviously! I seriously doubt Michelin's tweel is anywhere close to that 5.5 kg/T mark. It's more likely something like 12 kg/T. The purpose of this particular paper is not to show that tweels are better environmentally, it is to show an analytical framework for calculating the full-lifecycle environmental impact of tweels vs tires. Sort of like a "here are the equations, plug in real numbers later" kind of thing.
      - kbenson 5y ago
        Ah, nice to know, and thanks for giving a professional's assessment of what's being said. :)
        bkanber 5y ago
        :) Not a problem! Your experience hangs a lantern on one of the problems in academia. The authors of that paper did not intend to mislead -- this paper was published in 2011, likely written in 2010, only a handful of years after Michelin's unveiling of their gen 1 tweel design. To me, having been in the authors' position, I can easily tell what the true purpose of the paper actually was (the analytical procedure). But the authors had a secondary purpose driven by 'hype', almost, you could even call it click-bait: they wanted to make the tweel exciting so that other researchers would get interested in it and continue the work. One way to do that is by showing, from a materials perspective, that it is theoretically possible to design a tweel with a low rolling resistance, and given that, it's possible that tweels will be better for the environment over the full-lifecycle, including manufacturing and materials. And sure, this absolutely did/does deserve more research. However, the other issues with tweels, like NVH/comfort/etc, were 'out-of-scope' for that paper, and so they ignored those. Solving for those issues is what makes that 5.5 kg/T figure difficult/possibly impossible to attain. When these papers are confined to academia, it all works out, because most of the people who read your paper are other people who are writing papers, and they get it. But once these types of papers are picked up by the press/media/general populous, they can be very quickly misinterpreted! (To be clear, you didn't do anything wrong here, I'm just griping a bit about academia and pretending like I'm 'adding context' ;)
- bluGill 5y ago
  TPMS has been law in the US since 2007. People might be driving around with under inflated tires, but there is a light on if they are.
  - bkanber 5y ago
    My cold tire pressure is supposed to be 33PSI, my TPMS doesn't alert until it's below 28PSI, so there is a significant delta still. The TREAD law does not specify when TPMS must alert, other than the tire being 'significantly underinflated'.
    - loeg 5y ago
      The NHTSA has determined that the requirement is that TPMS alerts for 25% underinflation across any combination of tires, or 30% underinflation in a single tire.[1] Originally they wanted 20-25%, but determined that cheap TPMS sensors were not good enough to meet that threshold and did not want to impose the cost of better sensors. [1]: https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/TPMSfinalrule.pdf https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/TPMSfinalr...
  - loeg 5y ago
    TPMS doesn't alert until tires are something like 25-30% under pressure, which is pretty severe.[1] [1]: https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/TPMSfinalrule.pdf https://www.nhtsa.gov/sites/nhtsa.gov/files/fmvss/TPMSfinalr... (page 10)