Recently I built a new PC, switching from an Intel CPU to an AMD CPU, a Ryzen 5 1600. I am still using the GTX 1060 6GB graphics card I had in the old machine as well, but everything else is a new part.
I hadn't had any crashing issues in Dirt 4 at all while playing on that Intel system. I started to see fairly regular crashing due to an access violation with dirt4.exe once I started playing on this new machine- with the AMD CPU. I checked everywhere I could think of for a fix. I reinstalled the Nvidia drivers, played with or without MSI Afterburner running, changed graphics settings (including turning off the mirrors) and nothing seemed to make a difference. I figured it was probably an issue regarding the motherboard, since most other options were eliminated.
I was having an issue occasionally in other games, the error message being that there was no video memory available. I know that the graphics card works fine and has 6gb of video memory, because I could confirm that through dxdiag or the Nvidia control panel. Unigine Superposition benchmark also worked fine.
I ended up going to AMD's website and getting the latest chipset drivers for my B350 chipset (socket AM4) motherboard, and installed those. Since then, I haven't had an issue, but that's only with about 30 minutes of playing time- a few stages in the rain. So I just wanted to write this post here in case someone hasn't considered that option yet and hope that it will help anyone who could also be having this issue.