Valentino Rossi admits Michelin's MotoGP tyres have not so far suited the Yamaha, as post-season testing on the new rubber kicks off at Valencia.
Michelin returns to MotoGP next season after a seven-year absence, replacing former tyre war rival Bridgestone as the championship's control supplier.
After a number of tests through the season, the full field is making the switch for this week's two-day test in Spain.
Rossi, who is one of several riders to have crashed during the Michelin tests, said the early signs had not been good for Yamaha.
Asked how he thought the tyre change might affect form in 2016, Rossi replied: "It's impossible to say now because we don't know, but the first test with Michelin gave us some worries.
"It looks like our bike is not well balanced for those tyres.
"I hope it will just be a matter of time to set the bike up to work and make the Michelins work in the best way."
Earlier this year Michelin Motorsport director Pascal Couasnon told Autosport he was not surprised some leading riders were struggling to adapt to the French tyres' characteristics after so long on Bridgestones.
"We have to realise what we are asking of the riders is extremely difficult," he said.
"Sometimes they test during a week, then race at full speed on a specific tyre at the weekend, and then on a
Monday we ask them to switch, usually with a bike not totally tuned to our tyres to discover a different philosophy.
"It's true for every discipline each tyre maker has a different feel and philosophy, which is even more true for bikes.
"So for me it's not surprising we need a bit of time for the riders to get used to our signature, let's say."
The Valencia test runs through Tuesday and Wednesday, and is expected to feature the full 2016 MotoGP field.
The November sessions are traditionally the first chance for new rider and team combinations to get acclimatised, though this year there has been little movement during the 'silly season'.
The leading factory riders are all staying put, with the most notable changes being Scott Redding's switch to Pramac Ducati to replace Yonny Hernandez, and Tito Rabat graduating from Moto2 to take Redding's place at Marc VDS, where he is joined by ex-LCR rider Jack Miller on a new second Honda.
Lorenzo: “We are half a second slower than the last GP”
The new MotoGP™ World Champion Jorge Lorenzo talks about his relationship with Movistar Yamaha teammate Valentino Rossi.
Jorge Lorenzo discussed a variety of topics at the end of the official two day MotoGP™ test at the Ricardo Tormo circuit in Valencia.
On his relationship with teammate Valentino Rossi, Lorenzo admitted: “We have not yet spoke. I guess accepting not being able to win the championship will be tough, as it is for everyone. I imagine he will have to spend a few months away to return to normal.”
The subjects for discussion quickly returned to testing: “The test was very interesting because there have been many changes. The first day we only did one outing with the new electronics and the truth it that was a very radical change and I was a little scared. But the second there was not such a big difference form the old and little by little we were able to improve both the setting of the bike and the electronics.
“At this moment we must improve the electronics because we are half a second slower than the last GP. In this test I understood how to be faster with Michelin; the bike has improved, but we are still missing with electronics. The bike we tested in this test was more or less the same as Aragon. The fuel tank is located at the rear under the seat.
“The rear tyre has a lot of grip, especially in the central part, much more than before. In braking the front does not give much stability and you can’t push very hard. This is what happens when we spend many years running with a very good front tyre. With the new one we have not yet reached the level we had. There will still be falls until riders understand at what point in the corner there is more risk and adapt their style. “
