Mercedes team principal Ross Brawn believes Formula 1's ban on tire swapping played a major part in the return of his team's race day woes.
Just a week after the team appeared to have made a breakthrough in tire management with victory in the British Grand Prix, Lewis Hamilton and Nico Rosberg endured a tough afternoon at the Nurburgring.
Pole position man Hamilton complained all race about a lack of grip as he was powerless to stop main rivals Red Bull, Lotus and Ferrari finishing ahead of him, while Rosberg never recovered from the team's qualifying error that left him 11th on the grid.
Brawn reckoned that a combination of not being able to swap rear tires, plus high track temperatures on Sunday, exposed the ongoing weakness of the W04. When asked to explain why the team struggled so much, Brawn said: "The construction of the tire has changed and I think the ability to swap tires before was a good way of offsetting the stress of the tire.
"You could use it in qualifying and then swap it, and have it in a different condition for the race. You cannot do it with these tires, and I think we were back into going over the limit of the temperature of the tires and suffering from it.
"The first half of the race was pretty horrible. In the second half, the fuel weight went down, it got a touch cooler and we got back in the window again. The times were respectable, so it shows how critical we are. On high fuel at the beginning of race when we were trying to push, we overstressed the tire, and we need to find solutions to overcome that."
Although Mercedes' strong form in Monaco, Canada and Britain pointed to big strides having been made in tire management, Brawn revealed that he still had doubts ahead of the German GP.
"I never thought we were on top of the issues," he said. "There were some things like swapping tires on the rear that was helpful and that has disappeared.
"Silverstone wasn't that warm, and Montreal was not warm. I said we would need a hot race, and this [the German GP] was like some of the races earlier in the year where we struggled until things cooled down a bit."