Williams working to cool 2015 car

Williams happy for cooler temps in Shanghai

(GMM) First, the good news about Valtteri Bottas — he is no longer worried about his bad back.

"It is not giving me any more trouble," the Finn said in Shanghai on Thursday.

"With the new seat, I am using different muscles, because the legs are positioned differently."

A bigger problem for Bottas now is that, unlike the very end of 2014, he is no longer 'best of the rest' behind the two Mercedes.

Ferrari has stepped up to that role, while Williams is some way behind in third place.

In Malaysia, the problem for the FW37 was overheating rear tires.

"Our rear tires were hotter than we expected," Bottas confirmed. "This has an effect on traction," he is quoted by Auto Motor und Sport.

As teammate Felipe Massa revealed to reporters in China, the team has some new parts on the car this weekend.

"The tire problem has priority," chief engineer Rob Smedley confirms. "We are doing everything that might help: aero balance, setup, brake temperatures, drivability."

Bottas continued: "The car was actually designed to look after the rear tires more, so the problems in Malaysia were surprising."

Luckily, high temperatures should not be a problem in chilly China.

"We should be closer to Mercedes and Ferrari here," Bottas agreed.