First of all, make a copy of your controller config settings which are in your rF Userdata folder. I usually put the copy on my desktop. Then open up your controller config and scroll down to Force Feedback. Replace with the following values:
FFB Device Type="1"
FFB Effects Level="4"
FFB Gain="0.55862"
FFB Ignore Controllers="0"
FFB Throttle FX on steer axis="1"
FFB Brake FX on steer axis="1"
FFB steer vibe freq mult="0.00000"
FFB steer vibe zero magnitude="0.12000"
FFB steer vibe slope="0.00000"
FFB steer vibe wave type="0"
FFB steer force prediction="0.00000"
FFB steer force max change="100.00000"
FFB steer force neutral range="0.00000"
FFB steer force neutral function="0.00000"
FFB steer force exponent="0.78000"
FFB steer force input max="-11500.00000"
FFB steer force output max="1.00000"
FFB steer force grip function="0.00000"
FFB steer force grip weight="0.28000"
FFB steer force grip factor="1.00000"
FFB steer front grip fract="0.00000"
FFB steer update threshold="0.00000"
FFB steer friction coefficient="0.00000"
FFB steer friction saturation="0.00000"
FFB steer damper coefficient="0.00000"
FFB steer damper saturation="0.00000"
This should give you a nice starting point, but they are infinitely tweakable. For instance, you might prefer not to have the canned effects.
Alternatively there is this:
http://www.nogripracing.com/details.php?filenr=21410or this:
http://forum.racesimcentral.com/showthread.php?t=327696