Even before the season began, the 2002 tyre war between Michelin and Bridgestone was already well under way, with the French manufacturer building a new tyre with asymmetrical grooves. The tyre, however, was never used in a race after the FIA said it was illegal. Atlas F1's Will Gray talked exclusively to Michelin boss Pierre Dupasquier at the Malaysian Grand Prix, and the diminutive Frenchman explained why they don't agree with the sport's ruling body

Diminutive Frenchman Pierre Dupasquier has already achieved a great deal since his Michelin tyres arrived in Formula One last year, but as the season began he was pitched into a battle with the sport's governing body over a development which created controversy and led to suggestions that all the teams using his company's rubber would be disqualified in the season-opening Australian Grand Prix.

That, of course, did not happen, but after Dupasquier and his team backed down on their revolutionary groove plans to avoid problems with the FIA, he insists his designs were drawn to the word of the law. It is just a shame that Max Mosley and the technical rulers of Grand Prix racing put their foot down over an interpretation that was as clever as it was simple.

"The fact that we have to cope with grooves in the dry tyres is something that is very bad for the tyre," said Dupasquier. "For an engineer it is a pain in the neck because you like to put rubber on the ground not to put holes on the ground. We don't like it but it is a rule and we accept it, we understand it, and we have to minimise as far as possible the drawback from the grooves."

The aforementioned drawback is to do with the cornering ability of the grooved tyres. As the car travels around the corner, there is a sideways or lateral force that acts on the tyre. The four circumferential grooves on each tyre effectively split the tyre into five rubber ribs and because these ribs are narrow there is less support and the ribs deform.

"When the tyre goes around a corner it tries to push the rib and the poor tyre says 'oh, where am I?'" explained Dupasquier. "We were trying to reduce the effect when you give the order to the tyre and the poor thing doesn't know what to do.

"If you have a tread design like we have on the streets, they are designed to be strong laterally in the dry. But circumferential grooves are not like that and that is why we try to minimise the inconvenience. It was not an improvement in performance because we had less rubber on the ground and to put less rubber on the ground is negative, but it was supposed to give more stability to the tyre."

As diagram A shows, the standard tyre design has equal slopes on either side of the groove. But Michelin took advantage of the fact that the dimensions for the grooves are not strictly fixed, to develop a tyre which gave lateral support to the tyre in cornering.

"All the sizes are given as a minimum," explained Dupasquier. "They say 10mm minimum then 14mm minimum, which means you can go further than 14, you can have 18, 20, 21, why not? It just says that between those two dimensions you have to taper uniformly. And we asked English guys, we asked lawyers, what 'taper uniformly' means. It never said symmetrical. That is why we found it smart to propose this variant."

The design shown in diagram B shows that Michelin proposed different angles of taper for each side of the grooves, which reduced the contact patch (the amount of rubber which meets the track) but created a stiffer overall tyre. When tested by the teams, the prototypes were found to be a marked improvement on Michelin's previous offering as they reduced the drop-off in performance that appears to be solely associated with the French company's rubber.

"When you have a soft rubber and you push on the grooves, the rubber moves so at the beginning there is a scrubbing, a certain wear, and when this wear has lowered the ribs it behaves a bit differently," Dupasquier said of the Michelin tyres. "The level of performance was not better, but it was more constant, more stable, and the driveability was better.

"It was an attempt according to the words of the rule. Now we have been told (by the FIA) that we cannot do it, but we do not want to sue the FIA for anything. If they don't like it then fine, then we do something else. We spend our lives developing tyres so it is not a problem. There are many possible solutions.

"This subject is one of the thousands of technical discussions that we have with the FIA and the only reason why it is talked about is because the (FIA) president talked about it. He didn't say Michelin, he said 'tyre manufacturers are trying to do things' but somebody called me and said 'we asked Bridgestone this and they said it is not us, so it must be you'.

"It is only part of our development. When you are involved as an engineer in a mechanical sport you have a set of rules and you read it carefully and you try to interpret the rules the best possible way to have an edge on your competitors."

The chase for that edge, however, continually seems to end in controversy. It was a different concern that faced Dupasquier and his Bridgestone opposite number Hisao Suganuma in Malaysia as concerns developed that teams were running their grooved tyres down to a condition in which they virtually became slicks.

That is clearly not allowed, but the question is more about how far the FIA should go with policing it. Again, as in the case of the grooves, the difficulties are created by demands that the law is met to both letter and spirit.

"The rules say that the race will be held with grooved tyres, so if the tyre does not groove any more then it is not correct," said Dupasquier. But although it would be expected that as a tyre wears its performance deteriorates, the Michelin boss insisted that is not always the case.

"It depends what type of rubber you are talking about," he said. "On some types of rubber it may improve and some other kind it may, on the contrary, be deteriorating. We do not know about our rubber because we do not go as far as running them to slicks.

"Wearing down the grooves should show an improvement because there is more rubber on the track, but because of the degradation it is usually even. Normally we never see any improving during the race. With the load of fuel diminishing, it should be a significant level of improvement. They calculate it is between two tenths and five tenths per 10 kilos per lap, which is a lot, but you never see such an improvement because the car always degrades with the tyre wear."

These two controversies are not the first and they will surely not be the last to hit a pair of warring tyre manufacturers, but as the companies' development processes gather pace and the stakes become higher and higher, Michelin, Bridgestone and the FIA must all ensure they are speaking the law as well as reading it.