What are those black marks on race tracks?

Question

They're caused by hot tyres, but what *are* they actually? Rubber tyre molecules (whatever compounds they're made of)? How are they formed? Can someone describe the process in detail?

I also want to know if the marks can be removed, and how?

Answer 1

Great question.

The black marks on race tracks are called skid marks. In motoring terms, a skid mark is the residue tire rubber leaves when a car brakes hard. Skid marks can also come about when a car suddenly accelerates on a slippery surface, or takes a hard corner. This is also possible on bicycles. Basically its like taking a 20-year-old hardened pink eraser and trying to erase 30-year-old lead on an old piece of paper. You will end up with a pink skid mark.

Are they removable? Well, the simple answer is really no. The residue from the tires plates itself onto the ground like a paint-job. And its not like there is any type of big research going on to figure out how to remove skid marks... But my expert opinion is that if anyone actually >wanted< to remove them, they would find a way to do so. Probably by using some type of strong corrosive solution.

Answer 2

Basically those tire marks are caused by melting / burning "rubber" bonding with the pavement.

In almost all cases, the pavement is asphalt, and the rubber bonds with the petrochemical base that holds the aggregate (rocks) together.

The "skid" marks caused by locked brakes usually go away fairly quickly -- within a year. However, you can still see the burnout marks from the victory celebrations, or F1-style starts, for years.

To remove those marks, you basically have to remove the bonded carbonized "rubber" that has been melted into the pavement -- scraping off the top 1/8" of the pavement should do it, but then that looks even worse than the tire marks.