Hi Serge,
thank you for caring about my problems :-) But the problem with the rear brake was not about too much pedal travel or that i had to pump the pedal's pressure up. Because of that, I don't think that I need these residual valves.
Last year I used one master cylinder with two circles (0,75"). It was the same one as in the Porsche 911 from 1969, which has a great breaking performance. But this did not work very well. The Porsche has discs all around. The rear breaking of the Europa was insufficient. The brake shoes were as good as new after a three-hour-race. I tried to check the brake's effect in the workshop. When somebody stood on the brake and it was impossible to turn the front wheels, it was still not difficult to turn the rear ones.
In last winter I installed two different master cylinders (front: 0,7", rear: 0,625") and a balance bar system from Wilwood. I checked it again and rear braking seemed to be equal to front. Unfortunately I was not able to test it in a competition situation, because I had not even one lap with racing speed at the last race. So I'm still not sure, how to set the brakes up, yet. But it's interesting that Richard recommended the inverse master cylinder configuration that I am using. I am also using street shoes at the rear brakes.
Something good at the last race was that the braking was much more balanced than last year. In Hockenheim 2012 the front wheels stood immediately, while braking in rain. In 2013 there was never any standing wheel, while braking in rain. Although it was very slippery and I was not able to get the tyres warm.
What effect would it have, when I would switch the configuration of the master cylinders? I think that it would cause the fronts to break harder and the rears to brake less... But it that thought correct?
Best regards
Stefan