BARCELONA, Spain - Michael Schumacher has denied that frustration lay behind his criticism of Formula 1 tyre supplier Pirelli and said he was happy to have opened a wider debate about where the sport was heading.The seven-times World champion claimed the characteristics of the tyres had forced drivers to be more strategic and manage the rubber rather than being able to race flat-out every lap."They are so peaky and so special that we don't put the cars or ourselves to the limit," he asserted. "We drive like on raw eggs and don't want to stress the tyres at all.'I'M NOT FRUSTRATED'The Mercedes driver told reporters ahead of this weekend's 2012 Spanish F1 GP that he wanted to open a broader debate about "the principle of how Formula 1 should be".Schumacher said: "I am quite happy that we have initiated a discussion about how much influence one or another part should have in F1. It is certainly nothing to do with me being 'frustrated' because I haven't really been frustrated."I did a good race (in Bahrain) coming from 22nd and finishing 10th which I think was a positive result."Schumacher, winner of 91 races and the most successful driver in the history of the sport, has not been on the podium since he started his comeback with Mercedes in 2010 but said: "It's nothing to me, it's a general discussion that I wanted clearly to start to happen."TWO COMPOUNDSSchumacher won his last five titles at Ferrari with Bridgestone, a company particularly close to the Italian team, at a time when races were more like a series of flat-out sprints between pit stops. The Japanese manufacturer quit the sport at the end of 2010 and Pirelli returned as sole supplier.The Italian tyres are very different, Pirelli saying it was asked to make sure the rubber degraded more quickly to liven up racing and add another strategic element to the mix.With drivers having to use two compounds for each race, and their pace slowed by wear at different stages of that race, there is now a premium on tyre management.Stay with Wheels24 for the 2012 Spanish Formula 1 weekend.