where do tires go as they wear out?

What happens to all the bits of tire as the tread wears out?

Are they stuck on the road?

Floating in the air as particulate air pollution?

Going home to Jesus?

All three.

Actually, the last one depends on what religion they adhere to (pun intended).

FWIW, when I lived in NY, my window sill would fill with grit in an hour when the window was open. I was on the ground floor and someone told me that tire guck was the main source of that pollution.

But with all the tires in the us alone, you’d think there would be billowing storms of tire guck.

yup, and those nice white snow banks in winter that turn to yucky grey black sludge in a day or so?? tires.

Mostly on the road. If you watch auto racing you can tell where the good “line” is through the turn by seeing where the track is darkest. Sometimes it’s very obvious.