Felipe Massa thinks Williams has solved the issue which caused two separate punctures in the opening practice session of the Chinese Grand Prix weekend.
Massa suffered identical left rear blowouts in FP1 which were later attributed to contact with the bodywork of the Williams FW38. Massa and teammate Valtteri Bottas returned to the track in the afternoon after Pirelli found the failures were not caused by a problem with the tyre itself.
Massa points to the fact FP2 passed without incident as proof Williams has rectified the problem.
Asked if he had concerns for the rest of the weekend, he said: "I did long runs and did many laps and didn't have the problem again, so I think we found it and understood it. That's the most important thing.
"Everything went normally [in FP2], but it was just one session for me so it was definitely not a positive day. At least we found the problem and we need to work really hard to understand the tyres and try to be better tomorrow."
Bottas admits he was lucky not to suffer a similar puncture in the opening session.
"I had the same issue as well but was just more lucky. We think we managed to find the problem and we think we fixed it. It seems it was a bit of a problem with the rim clearance but I think we're on top of it. There's something under the rim, too close to the rim, inside the rim, that can cause problems."
"I had a good chat with the engineers before the second practice and they explained to me in detail what they found between the sessions and I felt confident going in the car. They found the problem. If something happens then it happens. There's no point fearing ahead of it."