Hi Stuggi,
I hope you understand English as I do not speak German. I had to translate your message using Google translator.
The Add On cars should not have caused a problem with your FFB (Force Feed Back) and as far as I know no one else has had it either so the cause could be that you installed something incorrectly. The only problem I had was with the sound but I think that was my fault.
Try this as it generally works for everyone: Go to the screen that the monitor is on and click on 'Options' <> 'Controller Force' (bottom right corner) and where it says 'Feedback Effects' change the value up or down and then back to it's original setting. You may feel the wheel jolt slightly. That's it now try it again.
If this does not work take your USB plug from the wheel out of your computer and put it back in again and try that.
If you still have problems trying re-installing the software that came with the wheel.
If all that fails then you could meticulously check that every Add On car file is in the right place, but I do not think that will effect your FFB at all.
Good luck and let me know how you get on.
Cheers,
Gee-Deeman
