Recently i have noticed a strange effect. In Project Cars2 i only have enabled: "gear shift", "wheels lock" and "wheels slip" however i receive vibrations  like (bzzzzz (1s), stop (1s), bzzzzz (1s)).

When car is not moving this effect is not active. Only when driving.

If you have any suggestions what that might be please let me know.

(Edit)

Now i checked it also in Dirt rally2 and it is also active. I tried to force the vibrations by maxing RPMs and turning hard on the gravel. For me it looks like the bass shaker cant produce constant vibrations for longer than 1s and it needs to take a break:)