YEONGAM, South Korea - Pirelli came under fire once more Sunday at the Korean Grand Prix, with Mark Webber lashing out at the tyre manufacturer and Sergio Perez warning a crash was "only a matter of time".In the build-up to the race Ferrari's Fernando Alonso had also hit out at the tyres, which have been the focus of criticism from drivers several times during the season for being too fragile.The front-right tyre on the McLaren of Perez exploded during the grand prix, with Webber picking up a puncture from the debris. Asked if it had been dangerous, Perez said: "Very. At the end of the day nothing happened (nobody was hurt)... but one day something will happen."'WE WILL REGRET IT'And asked if a rethink was needed for 2014, he answered: "Definitely, definitely. Nothing happened so after today nobody will comment on the situation, but one day something will happen so we will regret it."A clearly unhappy Webber, a plain-speaking Australian, was quoted as saying by Autosport.com: "That is how it is. The drivers aren't super-important - it is what other people want."He did not elaborate on to whom he was referring. However, it is understood that Pirelli was required by Formula 1 supremo Bernie Ecclestone to produce tyres that demand different strategies to make races more entertaining. Webber, who retired from the race over a separate incident (his car caught fire) not long after the puncture, said: "The tyres are wearing a lot and they also explode a bit - but that is for Pirelli to sort out."Webber, whose race was over when his Red Bull went up in flames, added: "Pirelli will put the puncture of Perez down to a lock-up but the reason the drivers are locking up is because there's no tread left."UNDER FIREPaul Hembery, Pirelli's under-fire motorsport director, defended the Italian manufacturer. Hembery said: "Regarding Sergio Perez's front-right tyre issue, we have been able to determine very quickly that it was the result of a flat spot caused by a lock-up under heavy braking."We're on exactly the same construction as we raced here in 2012, so there's no underlying problem, while flat spots or punctures have just always been an integral part of racing."Autosport reported that Hembery had apologised to Alonso before Sunday's race after the two-time World champion had similarly criticised the Pirelli tyres. An unamused Hembery had suggested in reply that Alonso ask World champion Sebastian Vettel if he wanted to know how to better manage his tyres, a key strategy of F1.Pirelli changed the design of the tyres after a series of dramatic tyre failures at the 2013 British GP in June, after which drivers had threatened to boycott the German Grand Prix if the problem was not solved.But drivers have continued to voice their displeasure. Stay with Wheels24 for the 2013 F1 season – fresh reports every day.