Here is patch for GP2 public release.
Patch includes:
New Physics by DaveSR1
The physics component of this update is as follows:
Tires have been tweaked to tighten up the mechanical (low speed) rear grip.
Brake optimum temperature range has been broadened to make the duct setting less critical This addresses the problem of the front brakes overheating into the fade range, making the rears tend to lock up. So now it is easier to set the brake duct so both front and rear remain in the right temperature zone. Still an important setup item though.
The aero package has changed to a setting range of 1 to 12, but with 3 DF packages, purchaseable in the upgrades section. There is the standard setup, (the default), and a High DF wing for tracks like Monaco or Hungary, and a Low DF wing for tracks like Monza. You will need to select the appropriate DF level before going to the track. Like they do IRL

http://www.drivingitalia.net/forum/index.php?app=downloads&showfile=785

Hard to believe no one has commented on this, amongst the regulars. From a quick try, this looks very nice and seems to drive well.

I am in business trip right now, so could not try it but checked thne link. Seems like there's lots of interesting stuff in that drivingitalia website.

Will try it when back home. Always interested in good open wheel mods

quite confused how to install this... the patch download gave me only SLS safety car

when I downloaded from other linked file, I got all selection of software folders but they did not look like something to copy/paste/extract into rFactor directory

From rFCentral, GP2 v2.0 COMPLETE, and then the separate Physics Fix seemed to do it. (No previous v1.0 install present.)
In the open-wheel slightly-less-than-fast-twitch-F1 category, this mod seems pretty good after a quick try with it.