Mercedes driver Nico Rosberg

The German team reversed the specification in Hungary because recent track outings showed that the hot engine exhaust was melting the car -- particularly the all-important floor and diffuser.

"The car looked different when it left the pits to when it came back," Michael Schumacher is quoted by Bild newspaper.

Mercedes was waiting on an order of incombustible space-craft material called Pyrosic, made exclusively by Pyromeral Systems in France.

But there were problems with delivery, with Ross Brawn confirming: "We are now trying a different material."

In Hungary, Nico Rosberg joined Schumacher in writing off their chances of winning the titles in 2010.

And asked what he can learn from Germany's leading F1 driver Sebastian Vettel, Rosberg answered: "From Sebastian?  Nothing -- only the speed of his car."