Michelin apologises to Rossi, Yamaha.

After conducting a detailed analysis of the front tyre problem that forced MotoGP World Champion Valentino Rossi to retire from the Chinese Grand Prix on May 14, Michelin has publicly apologised to the Italian and his Camel Yamaha team.

Rossi had charged from 13th on the Shanghai grid to fifth - and looked set to take a podium finish - when a chunk of rubber was suddenly thrown from the front tyre of his YZR-M1 on lap 16 of 22, destroying the fender and leaving The Doctor with a severe vibration (top picture).

The #46 rode on for another lap before being forced to pit for a tyre change. Unfortunately, both Rossi and his team assumed it was the rear tyre which needed replacing and the error was only spotted when Valentino exited the pits. Rossi was thus forced to retire, but even if the correct tyre had been changed, the Italian would have been lucky to score points.

After the race, Michelin immediately announced an investigation into the cause of the tyre problem - the results of which have now been released:

"On lap 16 of last month's Shanghai GP, Valentino Rossi had to pit due to excessive vibration from his front tyre, which was found to have been caused by the loss of a small piece of tread. The tyre remained inflated despite the missing piece of tread," read a Michelin statement.

"The analyses conducted at Michelin's Clermont-Ferrand HQ did not show any fault in the tyre. The same tyre specification was used by seven other Michelin riders in the same race without any trouble throughout the 22 laps.

"The very high level of stress experienced at Shanghai by the centre part of the tyre is the highest during the whole MotoGP season, because of frequent decelerations from over 320km/h to 60km/h within less than eight seconds. It would appear that this tyre could not sustain that level of strain; the safety margin we always include when we develop a tyre was apparently not enough in this particular case. The parameters that influence the levels of stress that a tyre undergoes are, among others: track layout, grip level, riding style and bike set-up.

"We apologise wholeheartedly to Valentino and the Yamaha team for having failed in this case to provide a front tyre capable of being competitive throughout the race. We have, of course, already taken all necessary measures, where physically possible, to ensure that such an event doesn't happen again."

Rossi suffered a further blow when he was forced to retire with engine problems at the following French Grand Prix, but bounced back with victory last time out at Mugello.

Round seven of the 2006 MotoGP World Championship takes place this weekend in Catalunya, with Rossi now 34-points behind joint championship leaders Loris Capirossi and Nicky Hayden.