Audi expecting tough weekend

Audi were unable to get any of their 2007-specification cars into the top 10 during practice, although Mattias Ekstrom was second fastest in Saturday morning's session.

However, the 2004 champion had struggled on Friday, and he admitted that he was not surprised that Mercedes have an advantage.

"Compared with Mercedes we're still too slow," said Ekstrom. "But it comes as no surprise to us."

Audi have not won at the German street circuit since 2002, but Ekstrom believes that they have been making progress at the track in recent years.

"This will be one of the most interesting races, as we have a duck since 2002 to break here," the Swede told autosport.com.

"Last year I felt that we were getting closer, so I'm looking forward to giving Mercedes a fight. But it won't be easy."

Ekstrom's teammate Timo Scheider is less optimistic for this weekend, as he has not run higher than 10th in practice.

"We're all having a difficult time at the moment," said Scheider. "During practice we only used one set of tyres so we've still got a bit of potential left, but that won't cover everything we are lacking."