Pirelli's Paul Hembery believes that Mercedes has resolved the tyre issues which impacted its performance earlier in the season.
The German outfit struggled early on with its new-spec W08 and its ability to sustain the temperature of its tyres - mainly Pirelli's UltraSoft compound - in their optimum working window.
Following its under-performance in Monaco, Mercedes went all-out to understand and solve its tyre issues. Hembery confirms that the Brackley squad has indeed settled its issues.
"The hard work paid off," the Briton told Germany's Auto Bild.
"What they did between Monaco and Canada was impressive -- a dramatic step," Hembery said in Geneva.
Hembery also played down recent speculation that Mercedes' struggle was amplified by an alleged advantage gained by Sebastian Vettel over the winter, as the Ferrari driver participated heavily in Pirelli's 2017 test programme.
"We would have liked more top drivers as committed to work as Sebastian was (to join him)," Hembery said.
"He gave us important feedback from morning to night, pushing us in the direction the drivers wanted, and we have to thank him because it makes a difference whether an inexperienced driver or one of the best tests tyres," he added.
Still, he thinks any advantage Vettel got was fleeting.
"If there was an advantage, it was at the very first winter test this year," said Hembery.
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