Pirelli is considering changing the structure of its tyres in the wake of the latest failure this season.

Paul Di Resta yesterday became the fourth casualty this year to have an issue with the rubber, with the Scot losing the tread on the left rear tyre of his Force India in second practice ahead of tomorrow's Spanish Grand Prix.

It brought an early end to Di Resta's session at Barcelona's Circuit de Catalunya, forcing Pirelli into another investigation as to the cause, with the outcome appearing to be a debris-induced cut.

Pirelli motorsport director Paul Hembery has no concerns with regard to the safety aspect, but appreciates from a visual point of view the incidents so far are not a good reflection on the Italian company.

"As a consequence of this year having a much more resistant belt pack made of very-high-tensile steel, it's very hard for any object to penetrate," said Hembery.

"So, with the few incidents we've had this year, which is not exactly higher in terms of statistics compared to previous seasons, the mode of failure has changed.

"Last year the tyre would have deflated completely and dropped down on the wheel, which is a failure people are more accustomed to seeing - but which is equally not as nice.

"This year the tyre is remaining inflated and the weak point becomes the tread, so when you get a cut it heats up and then goes away in one piece.

"With Paul's tyre we still haven't put all the pieces together, but if we take what we've seen in all the other three cases we've had we have always found a cut or something that has created the situation.

"We would like to find a way of changing that because it doesn't look very good from an image point of view."

Although changes to the structure of the tyre could be made, there would be consequences, according to Hembery.

"We would have to look at changing some parts of the structure, which is something we can do," explained Hembery.

"But we would need to balance that with what impact it might have on the teams because they have a lot of data that's based on this year's structure which influences aerodynamics.

"Also there is a lack of testing. Some of the solutions we might need would need some more extensive testing, so we are caught in between a bit of a rock and a hard place.

"But we do take these things seriously. We're looking at it to see if we can change this mode of failure, the visibility of it and turn it into something that is less dramatic from a visual point of view.

"It's a tough job being in the tyre business because things like this tend to go on film highlights, along with crashes and things like that."