F1 EXPLAINED: What does Tread Wear Indicator mean?

With the Formula One spending its well-deserved summer break, F1Technical's senior writer Balazs Szabo explains how the sport's sole tyre manufacturer Pirelli measures tyre wear.

Pirelli has been the sole tyre supplier in Formula One since 2011 following Bridgestone's decision to withdraw from the role at the end of the 2010 season.

The Italian manufacturer previously competed in Formula One from 1950–1958, 1981–1986 and 1989–1991. In addition to his role at Formula One as sole tyre supplier, Pirelli also supplies tyres for the FIA Formula 2 Championship , FIA Formula 3 Championship and F1 Academy, that form the feeder series to Formula One.

Pirelli engineer often use the TWI acronym which stands for Tread Wear Indicator. Just like road tyres, Formula 1 slicks have a physical indication to measure tread wear.

On their surface are six small cylindrical holes spread across the width of the tyre, with varying depths depending on their position. They are numbered from one to six, the first one located on the inner edge of the tyre.

At the end of every session, the surface where these TWIs are located is scraped using a special tool to remove debris and reveal the holes. The Pirelli engineers then insert a depth gauge in each one on all four tyres and measure how much the tread has worn.

This data is then compared and a percentage wear scale can be created from it, for all tyres from all cars, starting obviously from zero in the case of a brand-new tyre. The teams are provided with data from their cars along with recommendations for tyre use over long distances.