Help with DiRT

[Blackhawk47]

so i started playing again and everything runs silky smooth until i start the races which have 6 other people playing or more which i guess is taxing my cpu heavily. i know dirt still needs a decent pc to run but its almost unplayable on these races. im running all high with 2xaa. im thinking one setting stresses the cpu a lot but what setting is it ???

would appreciate any help as i used to run everything on low with my old 7800gt and i didnt encounter this problem. im thinking its particle settings but i really dont have a clue when it comes to game settings.

 

[snowdog]

Been awhile but does the game have any physics or particles settings?
Lower the sound quality too for more cpu power ( unless you've got a good standalone sound card).
Try lowering shadows one notch lower too, usually a tiny difference but a massive performance boost if you drop the shadow quality.