BARCELONA, Span - Pirelli has expressed concern about the alarming tyre failure suffered by Force India's Paul di Resta during Friday practice for the 2013 Spanish GP.The tread stripped off the Scot's still-inflated left rear tyre in second practice but Di Resta was able to bring the car safely to a halt.With drivers expressing safety concerns, Pirelli motorsport director Paul Hembery said the Italian company would investigate the issue.'IT LOOKS RUBBISH'"It obviously doesn't look pretty when you've the tread coming away like that," he told reporters at the Circuit de Catalunya. "Last year if we had failures it tended to collapse the tyre on to the rim so it still didn't look good. This year we are seeing the tread coming away so visually it looks rubbish. I don't like that."We're looking at it and seeing if there are things we can do to eliminate it.”Pirelli has already been attacked this season for introducing new compounds that wear and lose performance quickly, the idea being to increase the number of pit stops to liven up the on-track action..However there have been a number of failures, including one sudden deflation that led to Mercedes' Lewis Hamilton collecting a penalty in Bahrain for an unscheduled gearbox change."The tyre was still inflated from what I could see," said Hembery of the latest incident. "The structure didn't give way and that's what we've seen in a few other cases, that the tread is overheating and coming away." Stay with Wheels24 for the 2013 Formula 1 season – fresh reports every day.