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Hold on: The claim is this: > "Using a popular family hatchback running on brand new, correctly inflated tyres, we found that the car emitted 5.8 grams per ki
by ratel 7y ago
Hold on:
The claim is this:
> "Using a popular family hatchback running on brand new, correctly inflated tyres, we found that the car emitted 5.8 grams per kilometer of particles."
It does not seem to be a mistake:
> "Compared with regulated exhaust emission limits of 4.5 milligrams per kilometer, the completely unregulated tyre wear emission is higher by a factor of over 1,000."
A tire might way up to 15 kilograms for a 20 inch type. Lets assume 10 kilograms for a normal tire which is on the high side. 4 tires is 40 kilograms. Even if we assume half of the particals are not coming from the tire (but from where?). That still leaves 40,000 / 2.9 = 13793 kilometers for the tires to be completly consumed (weighing nothing anymore). That is definitely not happening.
So without an explanation on where the matter is coming from this does not read right.
- sschueller 7y agoMost of it must come from the asphalt.
- _rrnv 7y agoI agree. But tires do shed a lot. Consider a brand new tire has grove depth of about 8-10mm, and many drivers change tires when their groves are 0-2mm (yes, some idiots keep driving until they have slicks or "a pop").
- cormacrelf 7y agoTurns out you don’t need to measure air pollutants, you can just divide lost rubber by the distance travelled. It won’t be anywhere close to what was measured, but then again actual particles are a much more useful number because you can’t breathe a worn down groove.
- IshKebab 7y agoThen budget tyres surely wouldn't make a difference?
- kungtotte 7y agoThey're torn up from the road and rubbed off from the tyres themselves. The majority is obviously coming from the road. There's been studies done here in Sweden since we've banned studded winter tyres in some areas of Stockholm in an effort to reduce road wear and improve air quality. I don't know of any sources in English off the top of my head though. The last time I read an article about it though (2+ years ago, during Diesel-gate), the findings was that the danger in the particles comes from their size with smaller particles being more dangerous for humans. And that road particles were something like an order of magnitude larger than exhaust fume particles from diesel engines. We've since banned diesel engines inside Stockholm as well so the whole thing is moot here.
- blattimwind 7y agoThe studs in tyres are small carbide rods, which will easily chew through a soft material like asphalt. A rubber tyre would seem to be quite a bit softer than asphalt in colder conditions, so I have a hard time imagining the rubber wearing the asphalt down so significantly.
- gentleman11 7y agoI have been wearing studded slip on crampons when walking my dog this winter. The ice has been ridiculous, I’ve fallen twice already when not wearing them. Not great for the sidewalks, I know, but the dog needs his walks or he would... get sad
- thethrowboat 7y ago"Non-exhaust emissions (NEE) are particles released into the air from brake wear, tyre wear, road surface wear and resuspension of road dust during on-road vehicle usage."
- ehnto 7y agoRoads are filthy. Cody's Lab once did a video where he collected road dust from the side of a highway, and refined out all the precious metals from it. That's from one small section of highway, just imagine the scale of the pollution across the whole of the states. Concrete dust, rubber, metals, fuel, oil. Cars and car infrastructure is dirty business. https://www.youtube.com/watch?v=v5GPWJPLcHg https://www.youtube.com/watch?v=v5GPWJPLcHg
- stevenwoo 7y agoIf one are outside near any mountainous road here in Northern California, motor vehicles pass by with the odor of brake pad + brake disc (mostly brake pad?) near the bottom with a very strong, distinctive bitter sweet metallic odor and that's probably a tiny proportion of the material.
- jessaustin 7y agoNot sure if this test was set up to measure this, but brake dust, which contains all sorts of noxious particles, is a huge component of automobile emissions. This probably doesn't answer your question, however, because brake pads themselves only weigh so much...
- mycall 7y agoI thought brake pads use asbestos which contribute to the noxious particles. I do think Vehicle-to-vehicle communications will eventually minimize the all the chicken necking, evening out the traffic and thus less breaking.
- njarboe 7y agoElectric vehicles have regenerative braking when not braking hard. This dramatically reduces brake wear.
- Gibbon1 7y agoHybrids as well.
- cjensen 7y agoBrake pads have not used asbestos in several decades.
- jessaustin 7y agoNew pads on new passenger vehicles haven't, but it's still legal to use asbestos in aftermarket pads. https://parts.olathetoyota.com/what-are-brake-pads-made-of https://parts.olathetoyota.com/what-are-brake-pads-made-of
- gambiting 7y agoFitting or sale of automotive products containing asbestos has been banned in the EU since 2004 https://www.asbestosadvicehelpline.co.uk/is-asbestos-still-used-in-car-brake-pads/ https://www.asbestosadvicehelpline.co.uk/is-asbestos-still-u...
- npunt 7y agoExcellent use of back of the envelope math. I wonder if maybe the loss is non-linear, and a bit more is coming off because the tires are brand new. Perhaps there’s some coating on new tires before they ‘break in’?
- wool_gather 7y agoPerhaps, but that would have to be a pretty steep curve, and one would expect that kind of falloff to have shown up in the data here (unless they literally drove the car once for only 1km, which...would be its own problem for credibility).
- ta999999171 7y agoNot if everyone only reads the headline!
- allovernow 7y agoYep, I was going to say. I believe new tires may initially shed far material, the same way that they offgas for weeks.
- reidacdc 7y agoSome discussion down-thread about this also, somebody runs the numbers for the road itself. If the emissions numbers are right, it can't be matter that is being consumed or discarded, so it has to be matter that is being returned to the system and "emitted" again. Crap on the road itself meets this requirement -- a car drives by, throws up a bit of rubber off the tires, a bit of asphalt off the road, and a lot of junk from the road surface, and almost all of this stuff falls back on to the road to be thrown up again by the next car. The article doesn't say how the measurements were done, so it's possible they sampled a small fraction of the air and measured the density, so having the junk available to the sensor doesn't necessarily rule out the recirculation idea. But if the junk is mostly recirculating, then maybe the health threat is not as bad as if it's being emitted off the road and being lofted into the air with a long dwell-time? Lots of things are possible and consistent with what the article states, evidently more research is needed.
- salty_biscuits 7y agoRubber has a density of 1500 kg/m^3, a tyre wears about 5mm before it needs to be replaced. If I say a tyre has a radius of about 0.3 metres and a width of about 0.2 metres and plug this into the equation for an annular cylinder I get about 2kg of material lost between new and needs to be replaced per tyre. I don't know how long tyres last for most people, but I would guess about 50000km. So I would expect about 0.2 grams per km from tyres...
- Gibbon1 7y agoI did the calculation in Freedom Units and converted to grams per km. Assuming tires last 60,000 miles or 100,000km and got 0.1 gm/km. So matches your analysis closely. Notable I put 60,000 miles on my cars tires since I bought it. They are due for replacement kind of whenever.
- TheSpiceIsLife 7y agoI hadn’t heard the term Freedom Units before, seemed obvious what you meant, looked it up anyway. Universal measurements of American awesomeness. It encompasses all types of units (temperature, length, area, volume, speed, weight, GDP, etc). https://www.urbandictionary.com/define.php?term=freedom%20units https://www.urbandictionary.com/define.php?term=freedom%20un...
- WWLink 7y agoI would guess the measurement is more like how much dirt and dust is involved with a car driving driving down the road. Like brake dust, tire stuff.. and then that stuff being kicked up from the road surface by other cars and so on. And yes it's super filthy and gross. I live on a busy street (but not a main street, so not THAT busy)... and my bathroom windowsills turn black after about a month because of brake dust and other car grossness.
- telchar 7y agoA study linked last time this came up on HN indicated most of the particulate pollution is "resuspension", or previously generated particles kicked up by the car passing. It makes sense to consider in some cases but I think it's misleading to quote those numbers in some contexts, leading to confusion like this.
- nitin_flanker 7y agoCould there be an alternate way to measure the rubber wear off from vehicles? By considering the average distance after which a particular Sedan/SUV/Hatchback needs to change tyre, and then comparing the lost weights of old tyres and averaging that? I'm just wondering if there are any alternate ways to correctly measure this emission.
- yincrash 7y agoHypothesis: New tires have some break-in where they wear more than after the break-in period. To test- how much do 1 yr old tires emit?