Today with sunshine I was driving approx. 100 miles using different roads like motorway, nice mountain roads and streets in town. I feel ok with the decreased tire pressure to F 25 / R 27 psi. The grip is much better, as well as the response.
The new problem now is the vibration of the steerwheel passing 75 to 80 miles/hour. Back home I could find out that the wheels have to been balanced. The car came to me two months ago from the USA with new FIA wheels and brand new tires!!!!
That shows the good quality of the new tires
.
I hope balancing will stop the problem.
Thanks for your help.