Matt Somerfield writes:

The Bahrain Grand Prix saw a rise in tyre related issues with Ferrari's Felipe Massa seemingly coming off the worst, these were explained as being caused by debris when inspected at the circuit. The tyre failure of Lewis Hamilton however was the most controversial causing the Mercedes driver a grid penalty through virtue of a gearbox change. This couldn't be explained at the circuit and so went back to Pirelli's headquarters in Milan.

Paul Hembery of Pirelli subsequently had the following to say about the situation:

“We’ve had a detailed look at the tyre and debris from Hamilton’s car back at our research facility in Milan, and while we’ve been able to categorically rule out a structural failure of the tyre, we can’t exclude the possibility that the tyre was cut by some debris on the track.

“This seems to be very much the most likely explanation, particularly because Giedo van der Garde, who was following directly behind Hamilton, also sustained a very big cut on his tyre. From looking at the way the tyre broke up, it’s easy to see if the cause was internal or external in origin, and we can clearly see that it was external, which is why there is no reason for us to change any of our processes.

“Given the pattern of the other incidents during the same weekend, our 99% conclusion is that the tyre was damaged by debris on the track, which led to a rapid deflation.”

These failures seem consistent with the change in construction made by Pirelli for 2013 which allow the sidewall of the tyre to deform under load giving a more organic tread pattern as the tyre corners.

Debris collected by the tyre as it passes over it is given more freedom to cause damage by virtue of the tyre’s deformation. Tyre related failures are part of motorsport and not confined to open wheel categories so I see no reason for Pirelli to make adjustments to their product in the future.