5 ms·

Pneumatic tires are one of these things for which "reality has a surprising amount of detail" holds. Anyone who ever changed a standard tire on a bike can attes

by lqet 3y ago

Pneumatic tires are one of these things for which "reality has a surprising amount of detail" holds. Anyone who ever changed a standard tire on a bike can attest to that. There is so much going on: wires inside the tire for stability, cloth to withstand the air pressure (which the tube cannot), beads to interlock with the rim flanges to keep the tire in place (but only when pressurized), etc. I have witnessed bike tires where the bead/flange interlock wasn't perfect, and the inner tube was quickly swelling out between a small gap between rim and and bead until it burst with a bang that was louder than a gunshot. I once had a tire where the inner cloth was slightly damaged, and the tube was slowly creating a bulge in the tire over several days until it also burst. I found it amazing that all these counteracting forces still create something you can safely drive on, often for years, without problems.

repelsteeltje 3y ago
The movie clip of the Taiwan tire fabrication facility is very nice! We take so much of technology for granted.
tyingq 3y ago
The amount of energy in an inflated tire is surprising... https://www.youtube.com/watch?v=1VLhLcJJefo https://www.youtube.com/watch?v=1VLhLcJJefo
- gosub100 3y ago
  there's a whole subreddit for that (and other misadventures): /r/tiresaretheenemy
  - waterheater 3y ago
    Ever seen Rubber?
  - robocat 3y ago
    Apparently z-nails are inexpensive but excellent caltrops against cars and boy-racers.
- andrewflnr 3y ago
  To be fair, truck tires are an entirely different level than most car tires. More air at much higher pressure. I did some research on what actually happens if you try to slash a tire. A car tire is only slightly risky, but a truck tire can flay your hand.
  - ponector 3y ago
    And on the next level are tires of mining trucks, like that caterpillar 797 which can carry 300+ metric tons of rocks.
  - panarky 3y ago
    Please tell us more about your research. What is the safest method to vandalize car tires?
    - tyingq 3y ago
      Unscrew the inner valve stem and it's an annoyance that doesn't create permanent damage.
      - emodendroket 3y ago
        I suppose a more committed vandal could go on to do permanent damage after deflating the tires at reduced personal risk.
      - andrewflnr 3y ago
        One of the more evil variations I've heard of involves pinning a bb or pebble between the cap and valve pin, creating a slow leak that's invisible until you think to take off the cap.
    - TaylorAlexander 3y ago
      maybe a small drill bit in the sidewall
    - 00N8 3y ago
      NASA has actually looked into this & found the ideal method for safely vandalizing tires https://www.thedrive.com/news/nasa-built-a-tire-assault-vehicle-from-an-rc-tank-to-explode-space-shuttle-tires https://www.thedrive.com/news/nasa-built-a-tire-assault-vehi... (it's an RC robot w/ a drill, for testing how space shuttle tires perform when damaged)
- bumby 3y ago
  This is true for any compressible fluid. Work = -pressure * delta_volume. That amount of energy is why there are different standards for stress-testing something like a pipe, depending on the medium it's carrying. Occasionally you'll see an engineer or technician stress test a pipe carrying a compressible gas similar to one carrying a liquid. I can't remember the exact ASTM standards, but I think a compressed fluid should be tested to around 110% rated pressure and an incompressible fluid at 150%. If they use the wrong one on a compressible fluid, it's putting a lot more energy in the system. If it fails, it can be a bad day.
  - abfan1127 3y ago
    this is why people shouldn't pipe compressed air in PVC. PVC is rated for 300psi (iirc). However, it derates pretty quickly in cold temperature. If 150psi of air is pressurizing PVC pipe and it ruptures, its going to be a terrible day. Where if water pressurizes PVC pipe and it ruptures, its just a little messy.
bradley13 3y ago
Yup, pretty amazing. I had a bike that I rode a fair bit - same tires for 20 years. Back in the day, cars used to have flat tires pretty regularly - no longer - now some cars don't even come with the little donut wheels. It is genuinely amazing how reliable tires have become.
- jtbayly 3y ago
  Removing the spare tire is not an advance.
  - compiler-guy 3y ago
    Not having a spare is definitely a problem when you need it. But a spare is needed so rarely today. And that is a major, major advance. One hundred years ago, a car with two spare tires were not that unusual--tires were sufficiently unreliable that you might not manage a trip without _two_ flats, but tires improved, and now the only long-overland back-country adventurers carry two.
    - Syonyk 3y ago
      A hundred years ago, spare tires were also carried in a somewhat more visible and easy to access location. I'm sure "symmetry" was a consideration in having two as well.
  - kube-system 3y ago
    Spare tires under normal operation are dead weight which is the costliest possible engineering compromise to make on a vehicle, as it decreases every performance characteristic: acceleration, deceleration, cornering, fuel economy, etc. Their only reason for existing is to compensate for the historically poor observed reliability of tires. This has recently improved with TPMS mandates and better engineered tires.
    - jtbayly 3y ago
      AAA estimates 220 million flat tires annually in the US.[0] The existence of spare tires has nothing to do with poor observed reliability. It is because of lack of 100% reliability. It's because when people get a flat, they don't want to be stuck and have to be towed. They want to be able to do something about it and get back on the road. All my flats have happened not because I lacked TPMS sensors but because something poked right through. Low tire pressure only accounts for 15% of flats. [1] If you work for AAA, then sure, trying to convince people to get rid of their spares makes sense. But waiting around for AAA doesn't sound like a fun plan for me, especially when they won't be able to put a spare on for me, but will have to tow me somewhere. [0]: https://cluballiance.aaa.com/public-affairs/press-release https://cluballiance.aaa.com/public-affairs/press-release [1]: https://tiregrades.com/buying-guides/how-many-flat-tires-per-year-occur/#The_Importance_of_Spare_Tires https://tiregrades.com/buying-guides/how-many-flat-tires-per...
tpm 3y ago
Modern bike wheels and tires are also moving in an interesting direction: carbon rims are increasingly made 'hookless' (straight flange without the 'hook' which locks the tire bead) because it's easier to manufacture, lighter and more aerodynamic, while tires are tubeless, which is also lighter and less prone to punctures, but then the tires are harder to manufacture and more expensive. And lower pressures must be used so the tire does not pop off the hookless rim, so the rims and tires are also getting wider to hold more air, where once 17mm inner rim width was common for road bikes, we are now getting up to 25mm.
- ubermonkey 3y ago
  28mm is actually common. That's what I have on my brand-new Giant TCR (which is to say: an aggressive, go-fast road bike).
  - tpm 3y ago
    You are right 28mm is currently a common road tire width, but that's the total external tire width. What I mentioned rising from about 17 to (not yet common, but getting there) 25mm is the inner rim with - the narrowest measure between opposing rim flanges.
    - rhombocombus 3y ago
      As a recovering bike mechanic of 20 years (my retirement goal is to be able to afford doing that job again, it’s joyful but hard to make a living) the writing has been on the wall for several years about the many benefits of wider tires (and rims too I suppose). From fewer puncture flats, to greater comfort and traction, to actually lower rolling resistance, I dknt see a move back to narrower tires being something that ever happens and I couldn’t be happier about that fact! I’m too slow and old to reap any performance benefits, but my comfort and enjoyment of wider tires makes me ride my bike more. https://www.renehersecycles.com/bq-tire-test-results/ https://www.renehersecycles.com/bq-tire-test-results/
      - tpm 3y ago
slingnow 3y ago
If you found a bike tire this amazing, I can't wait for you to discover _anything even slightly more complicated than an inflated tube inside a rubber/cloth shell_. This reads like someone just came back from outer space and was stunned by the complexity of all of the systems that got them there. I'm all for appreciating the little things, but we have to draw the line with overdramatization somewhere.

by lqet 3y ago

repelsteeltje 3y ago

The movie clip of the Taiwan tire fabrication facility is very nice! We take so much of technology for granted.

tyingq 3y ago

The amount of energy in an inflated tire is surprising... https://www.youtube.com/watch?v=1VLhLcJJefo https://www.youtube.com/watch?v=1VLhLcJJefo

gosub100 3y ago
there's a whole subreddit for that (and other misadventures): /r/tiresaretheenemy
- waterheater 3y ago
  Ever seen Rubber?
- robocat 3y ago
  Apparently z-nails are inexpensive but excellent caltrops against cars and boy-racers.
andrewflnr 3y ago
To be fair, truck tires are an entirely different level than most car tires. More air at much higher pressure. I did some research on what actually happens if you try to slash a tire. A car tire is only slightly risky, but a truck tire can flay your hand.
- ponector 3y ago
  And on the next level are tires of mining trucks, like that caterpillar 797 which can carry 300+ metric tons of rocks.
- panarky 3y ago
  Please tell us more about your research. What is the safest method to vandalize car tires?
  - tyingq 3y ago
    Unscrew the inner valve stem and it's an annoyance that doesn't create permanent damage.
    - emodendroket 3y ago
      I suppose a more committed vandal could go on to do permanent damage after deflating the tires at reduced personal risk.
    - andrewflnr 3y ago
      One of the more evil variations I've heard of involves pinning a bb or pebble between the cap and valve pin, creating a slow leak that's invisible until you think to take off the cap.
  - TaylorAlexander 3y ago
    maybe a small drill bit in the sidewall
  - 00N8 3y ago
    NASA has actually looked into this & found the ideal method for safely vandalizing tires https://www.thedrive.com/news/nasa-built-a-tire-assault-vehicle-from-an-rc-tank-to-explode-space-shuttle-tires https://www.thedrive.com/news/nasa-built-a-tire-assault-vehi... (it's an RC robot w/ a drill, for testing how space shuttle tires perform when damaged)
bumby 3y ago
This is true for any compressible fluid. Work = -pressure * delta_volume. That amount of energy is why there are different standards for stress-testing something like a pipe, depending on the medium it's carrying. Occasionally you'll see an engineer or technician stress test a pipe carrying a compressible gas similar to one carrying a liquid. I can't remember the exact ASTM standards, but I think a compressed fluid should be tested to around 110% rated pressure and an incompressible fluid at 150%. If they use the wrong one on a compressible fluid, it's putting a lot more energy in the system. If it fails, it can be a bad day.
- abfan1127 3y ago
  this is why people shouldn't pipe compressed air in PVC. PVC is rated for 300psi (iirc). However, it derates pretty quickly in cold temperature. If 150psi of air is pressurizing PVC pipe and it ruptures, its going to be a terrible day. Where if water pressurizes PVC pipe and it ruptures, its just a little messy.

bradley13 3y ago

Yup, pretty amazing. I had a bike that I rode a fair bit - same tires for 20 years. Back in the day, cars used to have flat tires pretty regularly - no longer - now some cars don't even come with the little donut wheels. It is genuinely amazing how reliable tires have become.

jtbayly 3y ago
Removing the spare tire is not an advance.
- compiler-guy 3y ago
  Not having a spare is definitely a problem when you need it. But a spare is needed so rarely today. And that is a major, major advance. One hundred years ago, a car with two spare tires were not that unusual--tires were sufficiently unreliable that you might not manage a trip without _two_ flats, but tires improved, and now the only long-overland back-country adventurers carry two.
  - Syonyk 3y ago
    A hundred years ago, spare tires were also carried in a somewhat more visible and easy to access location. I'm sure "symmetry" was a consideration in having two as well.
- kube-system 3y ago
  Spare tires under normal operation are dead weight which is the costliest possible engineering compromise to make on a vehicle, as it decreases every performance characteristic: acceleration, deceleration, cornering, fuel economy, etc. Their only reason for existing is to compensate for the historically poor observed reliability of tires. This has recently improved with TPMS mandates and better engineered tires.
  - jtbayly 3y ago
    AAA estimates 220 million flat tires annually in the US.[0] The existence of spare tires has nothing to do with poor observed reliability. It is because of lack of 100% reliability. It's because when people get a flat, they don't want to be stuck and have to be towed. They want to be able to do something about it and get back on the road. All my flats have happened not because I lacked TPMS sensors but because something poked right through. Low tire pressure only accounts for 15% of flats. [1] If you work for AAA, then sure, trying to convince people to get rid of their spares makes sense. But waiting around for AAA doesn't sound like a fun plan for me, especially when they won't be able to put a spare on for me, but will have to tow me somewhere. [0]: https://cluballiance.aaa.com/public-affairs/press-release https://cluballiance.aaa.com/public-affairs/press-release [1]: https://tiregrades.com/buying-guides/how-many-flat-tires-per-year-occur/#The_Importance_of_Spare_Tires https://tiregrades.com/buying-guides/how-many-flat-tires-per...

tpm 3y ago

Modern bike wheels and tires are also moving in an interesting direction: carbon rims are increasingly made 'hookless' (straight flange without the 'hook' which locks the tire bead) because it's easier to manufacture, lighter and more aerodynamic, while tires are tubeless, which is also lighter and less prone to punctures, but then the tires are harder to manufacture and more expensive. And lower pressures must be used so the tire does not pop off the hookless rim, so the rims and tires are also getting wider to hold more air, where once 17mm inner rim width was common for road bikes, we are now getting up to 25mm.

ubermonkey 3y ago
28mm is actually common. That's what I have on my brand-new Giant TCR (which is to say: an aggressive, go-fast road bike).
- tpm 3y ago
  You are right 28mm is currently a common road tire width, but that's the total external tire width. What I mentioned rising from about 17 to (not yet common, but getting there) 25mm is the inner rim with - the narrowest measure between opposing rim flanges.
  - rhombocombus 3y ago
    As a recovering bike mechanic of 20 years (my retirement goal is to be able to afford doing that job again, it’s joyful but hard to make a living) the writing has been on the wall for several years about the many benefits of wider tires (and rims too I suppose). From fewer puncture flats, to greater comfort and traction, to actually lower rolling resistance, I dknt see a move back to narrower tires being something that ever happens and I couldn’t be happier about that fact! I’m too slow and old to reap any performance benefits, but my comfort and enjoyment of wider tires makes me ride my bike more. https://www.renehersecycles.com/bq-tire-test-results/ https://www.renehersecycles.com/bq-tire-test-results/
    - tpm 3y ago

slingnow 3y ago

If you found a bike tire this amazing, I can't wait for you to discover _anything even slightly more complicated than an inflated tube inside a rubber/cloth shell_. This reads like someone just came back from outer space and was stunned by the complexity of all of the systems that got them there. I'm all for appreciating the little things, but we have to draw the line with overdramatization somewhere.