Ferrari technical director Ross Brawn has confirmed the role of his team in the Michelin complaint. The Italian team went to Charlie Whiting which resulted in the warning letter to the other F1 teams. The FIA said that "as Ferrari have confirmed, it was they who pointed out to the FIA Technical Delegate that tyres which had a tread width of 270mm when new, appeared to be using a greater tread width when in use. Having checked this information, Charlie Whiting warned the relevant tyre company informally immediately after the race in Hungary. On his return to the office three days later he wrote to inform all the teams.
"The rules are not concerned with parts of the tyre which make occasional contact with the track or kerbs, but parts which are in regular or systematic contact with the track and thus constitute tread. There is reason to believe that the tyres in question may not be identical to those in use at the start of the season. If they are used in Monza in combination with a car set-up which gives more than 270mm tread width, the stewards and, ultimately, the FIA Court of Appeal will have to decide if the rules have been broken."
Although Michelin has said that it has a written confirmation from the FIA that its tyres are legal, the validity may be voided if different car setups have been used to check that validity.