If your system has one disk, then that is the place to start.
1's and spike at times, but not be over 1 for 10 seconds, etc.
You will probably see that disk at 100% a lot and disk queue length well over 1 - and that isn't good. Use windows resource monitor while you play. The system is not able to load textures from disk fast enough, and that will result in exactly this. Freezing while driving fast usually indicates disk I/O is the bottleneck.
