This concerns the large pieces of rubber that come off the tires of semi tractors and trailers.
When my son was about five and we were driving on the freeway, I told him this was wild rubber that was run over while trying to cross the interstate at night. He believed that for a couple of more years before finding out the truth.
A childhood belief about cars

others believed things like this
- I used to believe that Electricity was chiped overseas in large thick rubber boxes on ships.Anon
- My dad told me that the reason Birds didn't get electrocuted on overhead wire was they had rubber feet!!— Derricki
- I had an 18 lb. cat who ate rubber bands, I used to believe she could bounce away if not careful.— Dawn
- I used to believe that your brain was a red rubber ball inside your head.— Greg
- I used to believe that if I swallow chewing gum, a rubber tree will grow on my head!— Farry Aprianto
- I believed travel trailers had a pool on top because the curved ladder was the same.Anon