Have you tried the tuning menu for the car when you select it? There are I believe ten ffb settings...5 is default... I used 3 but that was in the sauberI'd like to have a go, but when on the server tonight trying some lappage i found that the ffb on my Porsche went all weird at the end of the long back straight so i wasn't in control. I tried it with max aero at the front too, just to check that wasn't the issue. Vid below:
It's not very often i crash in simracing, but i was flying off the track constantly at the same corner because the ffb went floaty and weird!