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Every year millions of car tires are worn down on our highways, yet the roads are not all black from the rubber, neither are the sides of the roads black. Where does all the rubber go?

meowmafia
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    Tire dust. Into the air or onto the road (and then washed or blown away). Not a Physics SE question, I'd say. – Řídící Oct 11 '13 at 10:54
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    The rubber and the road surface annihilate each other. Potholes are proof of this. – Olin Lathrop Oct 11 '13 at 12:36
  • Let's say 5mm of rubber worn off a 150mm wide, 30cm diameter tyre in its $10^8m$ life. Each car therefore lays down about $5.7\times10^{-11}\mathrm{m^3}$ of rubber for every metre of road. A major major freeway with say 10 cars a second and this is about $500\mathrm{cm^3}$ of rubber laid down for every metre of road in $10^6$ seconds (about two weeks - in between rain storms) or about 25 grams per square metre. So there's a bit of dust on major highways, but not as much as you might think. – Selene Routley Oct 11 '13 at 12:55
  • To live with all of my left socks? – RBarryYoung Oct 27 '13 at 19:16
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    I'm voting to close this question as off-topic because it is not about physics. – ACuriousMind Dec 23 '15 at 18:02
  • @ACuriousMind Agreed that it's not strictly physics, but it's a pretty good Fermi question which Rod Vance took on well. And Fermi questions are always good physics-thinking exercises. – Bill N Dec 23 '15 at 18:18
  • @OlinLathrop :) Good hypothesis. What's your experiment, and how do you intend to falsify the hypothesis? – Bill N Dec 23 '15 at 18:19

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First, "all that rubber" is really a very small quantity when spread out over all the road surfaces. Second, you sometimes do see rubber marks on the road. This is especially true on concrete roads where the surface is light colored. Asphalt is dark, so much of the rubber markings are not obvious.

Since so little rubber gets deposited per time on a normal road under normal use, most of it gets washed away by rain or blown away by wind, then dispersed so much that we don't notice it. The sides of roads are more dusty places than a few meters further from the road.

Again though, in most cases the total quantity of tire rubber in any one place is so small that we don't notice it.

Olin Lathrop
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  • I'm not sure, but I would think that skid marks (on roads, but also especially on racetracks, airfields) are not of the normal dust-variety and are not as easily removed. – Řídící Oct 11 '13 at 13:18
  • @aufkag: Right, so that type of tire wear stays on the road such that we are more likely to see it. As I said, sometimes you do see rubber marks on the road, so I fail to see whatever point you are trying to make. – Olin Lathrop Oct 11 '13 at 13:46
  • No point whatsoever. Just a random remark. :) – Řídící Oct 11 '13 at 13:49
  • have to check whether new tyre and used tyre have the same mass i.e, the grooves are smoothened and leveled upto groove depth? –  Oct 11 '13 at 13:55
  • @Waqar: Obviously they don't have the same mass. Material is lost. That's the whole point of the question. – Olin Lathrop Oct 11 '13 at 14:48
  • It adds up to quite a large quantity and it ends up as microscopic particles of rubber/carbon/metals/sulfur compounds in water supplies near the roads. There is a lot of concern about what it does to marine life – Martin Beckett Oct 11 '13 at 15:40
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The rubber which wear's out from the tire's are very small in size and yes they are in very small quantities and it blow's way in he wind and goes away on a world wide trip

If you want see the wearing of the tire's and accumulating on the road the skid mark's are good example and you want to see even more then watch the starting points of the track of drag races where the racer's do the burnout you can see the weard-out rubber and if they allow you on the track you can event take them on your finger tip's.

Deiknymi
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Most of it is so small it goes into the atmosphere . It would probably show up on a good test.

Mike Murphy
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