F1 EXPLAINED: What does porosity mean?

With the Formula One spending its well-deserved summer break, F1Technical's senior writer Balazs Szabo explains how surface porosity can lead to premature degradation.

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.

Formula 1 tyres develop surface porosity as a result of the intense mechanical and thermal stress to which they are subjected. The tyre deforms, especially under acceleration and braking, more so on rough surfaces and this causes energy and heat to build up in the compound.

If temperatures exceed the optimal operating window, microcavities and surface irregularities can form and this surface porosity can lead to premature degradation.

Microcavities can also lead to the formation and expansion of gas or vapour bubbles, known as blisters, between the carcass and the tread. Excessive wear can partially separate the rubber layers and these bubbles can evolve into craters or holes on the tread surface.

This is known as blistering, visible usually as dark streaks or damaged areas on the tread. This phenomenon is more common on a track that is not rubbered-in much, with high surface temperatures and with a very aggressive driving style.