Pirelli delay race debut of revised F1 tyres

London: Pirelli have shelved plans for Formula One teams to race with new-specification tyres in Canada next week, a company spokeswoman said on Wednesday. She said the modified rear tyres would now be used only in Friday practice in Montreal for evaluation purposes, with each team given two sets, with the hope that they could then be used in the race at the British Grand Prix at the end of June.

"The regulations allow us to bring a set of experimental tyres to Friday practice," explained the spokeswoman. "We decided to do it that way which gives everyone a chance to test them and hopefully all agree."

Pirelli want to restructure the tyres to incorporate a 2012-style inner belt made of kevlar, rather than steel, after a spate of failures caused by debris. The supplier is keen to eliminate 'delaminations' - where the tread separates from the body of the tyre without it deflating.

However any change would have to be approved by all the teams, unless the governing International Automobile Federation (FIA) orders it on safety grounds - which has not been the case.

Champions Red Bull have been vocal in calling for the 2013 tyres to be made more durable to reduce the number of pitstops and allow drivers to race harder. Others such as Lotus, Ferrari and Force India are against the changes because they have got their cars working well with the compounds.

Pirelli have also come under fire for carrying out a 'secret' tyre test in Spain with Mercedes after this month's Spanish Grand Prix. The matter has been referred to the FIA, who could pass it on to their international tribunal, after protests by Ferrari and Red Bull at last weekend's Monaco Grand Prix.

Testing is banned during the season, although Pirelli have it written into their contract that they can carry out a number of 1,000-km tests with a representative car. Red Bull principal Christian Horner said Mercedes, winners in Monaco, had acted in an 'underhand' manner by not telling others about the test. He suggested they had gained an advantage by running a current car on tyres to be used later in the season. Pirelli have disputed that, saying Mercedes did not know what they were testing.