Mercedes pair Lewis Hamilton and Valtteri Bottas have both reported "challenges" with the tyres after they completed another half day of running each in Barcelona.
Bottas added 86 laps to his tally, while Hamilton racked up another 91 laps on Tuesday as they finishing P2 and P4 respectively in the day one standings.
However, the Mercedes W09 is struggling to get the medium tyres up to temperature and suffering from too much degradation on the soft tyres, causing them to blister.
“The biggest challenge we faced today was to get the tyres working properly on this new track surface,” Hamilton said.
“The medium tyre was difficult to get working; the soft tyre is better for warm-up, but suffered with degradation. We are learning all the time.
“It's been a good day. We've got through everything we needed and put good mileage on the car – it's been productive.”
Bottas echoed the thoughts of his team-mate, saying the tyres have presented issues which the team have had to manage.
“In these weather conditions we start to really work the tyres and we had a few issues to manage,” Bottas added. “So we had a few more challenges with the tyres than we had last week, but at least now they can warm up.
“We keep discovering more about the new car, learning how it reacts to different settings. We did more than 80 laps – so more than a race distance, a really good mileage.”
The Merc duo will continue to split duties on Wednesday, with Hamilton taking the morning session.