I finally found a good setup.
But I got a bad tire wear... the front and rear right tire becoming rills at the inside just after 10 runs. The car is then undriveable.. new tires and all is good.
All my club colleagues are running these tires (Solaris 35) without any problems for 30-40 runs. Of course the tires are slower then but its still the same feeling.
Whats wrong with my setup?
I use 17.5 motor... not too fast for the tires