What name is given to the small pieces of tyre rubber that gather by the side of a Formula 1 track?

Formula One (also known as Formula 1 or F1) is the highest class of international auto racing for single-seater formula racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The World Drivers' Championship, which became the FIA Formula One World Championship in 1981, has been one of the premier forms of racing around the world since its inaugural season in 1950.

As Formula 1 tyres are used, small pieces of rubber that are shredded from the tyres during cornering are throw off. These are little curls of rubber that accumulate on the side of the track. As a grand prix weekend goes on, especially during the race when the track can’t be cleaned, this build up of rubber off the racing line can become incredibly difficult to drive on. Running onto them mid-race can be treacherous as they prevent the tyre making proper contact with the road, thereby reducing grip.

Drivers liken it to racing on marbles – hence the name. This is one of the reasons why overtaking a rival off the racing line can be incredibly difficult.