2-75. Where Did Your Tires Go?


Winter is coming. For those that live in the snow belt, it’s time to think about switching over to snow tires or at least check the all-seasons to make sure there’s enough tread there. Most modern tires have tread-wear indicators, but there’s always the tried and true Lincoln test…. stick an upside down US penny in the tread, and if you can see Lincoln’s hair, think about getting new tires.

But… when the tires were new, poor Lincoln had most of his head buried in there. Where did the rubber go? I first thought of this when I was staying with a friend in the city. Though she was fastidious, there was a fine layer of dirt on the windowsills. It was pure black—much blacker than the dust I was used to in the country. And there was a lot of it. Outside the window there was a constant stream of traffic, and I thought maybe the dust was caused by diesel exhaust. And no doubt, some portion of it was, but the bulk of it was rubber from tires.

Tires wear constantly as long as a vehicle is in motion. If you’re braking or cornering, they wear faster, and if your tires are under inflated, the wear MUCH faster. Snow tires have more traction, and that also means more rolling resistance, so they wear faster. And those big gnarly off-road tires? They wear really fast on pavement, as do the tires on four-wheel drive and all-wheel drive vehicles. There’s a trade-off between traction and tire conservation, and generally you want to err on the side of traction.

When the rubber wears, two things happen. Tiny particles enter the air and stay there until they hit something like a windowsill or the inside of your lungs. Large particles end up as dirt on the side of the road, and then eventually in our waterways as rain washes them away.

How much rubber are talking about? Millions of tons. And it’s not just latex—tire rubber is a mixture of compounds, including some heavy metals which can be harmful in quantity. Also, the latex itself can cause problems in people with a sensitivity.

So what do we do about this problem? There’s really not much we can do except reduce the number of cars on the road. Tires that don’t wear down don’t have traction, so better wearing tires can only offer so much of a solution. If you’re really sensitive, you might consider moving out of the city and away from highways.

Recently, when cleaning the windows inside our downtown Chicago mid-rise apartment, I notice something odd. Not only was the dirt very black, like tires, but it was also glittery. It seemed that there were tiny particles of metal in there as well. Could this be from the wheels of the elevated train that runs every five minutes just outside? Possibly. But rather than panic about all the substances that are “out to get me,” I think I’ll just take comfort in the fact that I’m living under these conditions with literally millions of neighbors, and we seem to be doing just fine.

And if I’m wrong, there’s very little that can be done about it.

Lincoln's thinkin' that it's time to get new tires.

Lincoln’s thinkin’ that it’s time to get new tires.


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