I guess driver feedback isn't your strongpoint . . .
Okay, you've got a bottoming out problem. So the obvious thing to do is raise the ride-height and stiffen the suspension as much as is possible.
Beyond that . . . which circuit are you at? How is the car handling? Understeer? Oversteer? On entry or exit? What settings are you currently running? How are your tyre temperatures central, in and off? How do you like a car set up anyway?
We'd kinda need more info is what I'm getting at. Rfactor has got a pretty spiffing physics model and saying "My car don't work, you make it work" isn't going to cut the mustard.