Factory Ducati rider Jorge Lorenzo says he still does not feel comfortable on the Desmosedici GP18 after a difficult day’s testing in Thailand.
The Spaniard was 10th-quickest on the second day of the Buriram pre-season test - 0.760s off pace-setting Repsol Honda rider Marc Marquez - and was hampered by chassis issues in the morning.
“We’ve had some problems in the first bike this morning that [there] was some little fissure in the chassis, so we had to put away this bike and we exit with the second bike, something was broken,” Lorenzo said.
“Then it was very slow, I was one second slower than in the morning.
“Anyway I still don’t feel comfortable, even with a good bike I am still far from the fastest one, especially Marquez who is very strong here.
“But obviously in the afternoon with the other bike, I was even worse. So I think we need to understand the new bike because some points very positive but also some negative points.
"So we need to understand a lot of things.”
His reaction is in stark contrast to the Sepang test, during which Lorenzo topped the second day and said the Ducati was much closer to his natural riding style.
Teammate Andrea Dovizioso trialled a new chassis on Saturday - as well as getting further mileage with the new fairing he tried on Friday - ending the session one place ahead of Lorenzo in ninth.
“I'm happy about the speed we showed today but still we are working with the fairing and the chassis,” he said.
“We had a chance to make a lot of work today, new fairing we understood more and the chassis is very similar as the old one, but it is very difficult to fix something big normally when you change a chassis.
“We continue to work more in the details. Fortunately, everything we try, it works, still we didn't understand very well if it is better to use the new things or not, but in any case our speed is really good.”
A decision on fairings has split the riders, as while Lorenzo says it is “much better” with the new fairing, Dovizioso remains undecided.
“The fastest lap, I did with the fairing with the winglets but doesn't mean it is the right fairing to use,” Dovizioso said.
“I don't want to entry the details but there is a positive and negative and I think the work of the team and what the rider can understand, it is difficult to understand.
“It can make a big difference during the season like we did last year. We still didn't take a final decision but we are working very hard in that way.”
Additional reporting by Oriol Puigdemont