Today we have added a file by Wombat778 that attempts to fix the issue that many rFactor gamers have using an nVidia graphics card.
This is an attempt to fix an incompatibility that causes very low FPS in rFactor when using many NVIDIA cards (most common on the 8800 series). The problem is caused by the way that these cards allocate memory for vertex buffers.You can download this file from here.
Quite a few people have been using this fix for a while, and it seems to produce between a 50% to 100% improvement in FPS, especially at the back of the grid. For unknown reasons, however, certain people are not affected by this problem and actually see reduced performance with this file. Your mileage may vary. Please also note that a few people with ATI cards have reported an improvement.
Finally, this also appears to work in at least some other games based on ISIís engine, including GTR2.