Barcelona MotoGP tyre situation complicated in heat - Jorge Lorenzo

The Yamaha rider set the pace on Friday afternoon, and was second to Suzuki's Maverick Vinales in the morning session.

Riders up and down the order expressed concerns over the durability of Michelin's tyres in hot conditions - even the hardest of the three rear compounds - when paired with the low-grip Barcelona surface.

With similar conditions expected for Sunday's 25-lap race, Lorenzo said teams and riders would have their work cut out.

"With the rear tyre Michelin has brought this weekend it's not easy," he said.

"It's quite complicated, everyone is struggling to keep a high pace.

"[Yonny] Hernandez did a small run, but apart from him nobody did more than five or six laps in a row.

"This will be very important, to understand the rear tyre when you have done more than seven, eight laps, what the pace will be.

"But for the moment we are the ones who have the pace, and we had 11 laps [in total on Friday] in the 1m42s, so this is great to have a great feeling for the race.

"We still have two practice sessions to do, we still have to decide which tyre is going to be the race tyre, especially in the rear."

Lorenzo set his time with the hardest rear tyre, while some near the top of the order, including Honda pair Cal Crutchlow and Dani Pedrosa, opted to try the softest on Friday afternoon.

Pedrosa's factory Honda team-mate Marc Marquez used the hard compound and finished ninth, 0.773 seconds off Lorenzo's pace.

He did, though, suggest that the medium tyre could be used on Sunday.

"I kept all the same tyres for each session to try to understand the set-up," Marquez said.

"After 15 laps, you are on the limit if you use the medium front, but I did all the sessions with the hardest front we have here and it looks better, much better.

"You have less confidence, but it looks like it will be the race tyre.

"The rear is more of a question mark. It's more open.

"The medium one looks like it's not so bad, for example I rode all the session with the hardest one and we must understand more."