Ross Brawn believes the race-day woes Mercedes have struggled with for most of the season is related to the ban on tyre-swopping.
After appearing to make a breakthrough with the way the Mercedes cars managed their tyres with a victory at the British Grand Prix, drivers Lewis Hamilton and Nico Rosberg struggled at the Nurburgring this past weekend.
Hamilton started on pole but struggled with grip throughout the race, while Rosberg was unable to mount a challenge at any point in the race after a poor qualifying session left saw him start from 11th.
The Mercedes Team Principal believes the high track temperatures as well as the inability to swop rear tyres exposed the weakness within the W04.
"The construction of the tyre has changed and I think the ability to swap tyres before was a good way of offsetting the stress of the tyre," Brawn explained.
"You cannot do it with these tyres, and I think we were back into going over the limit of the temperature of the tyres 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 tyre, and we need to find solutions to overcome that."
Brawn admitted that he was unconvinced about the apparent Mercedes revival following strong performances in Monaco, Montreal and Silverstone.
"I never thought we were on top of the issues," he continued.
"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."