Lowering vibration settings has no effect

Ok some progress: I have lowered "audioeffects" in G Hub to 0 and then checked the box "apply settings in game" (which for some reason greys-out audioeffects) and now the ingame settings seem to have an effect, I lowered curbs to 0 and there was no rumble anymore when going over the curbs.

However there is still some very annoying kinda rattling noise/vibration when driving in highspeeds and the purposing effect starts to kick in, you know when you also hear the pff pff pff on the TV, the worst is probably in Las Vegas, it's almost constant vibration on the straights. I thought that this are the onroad effects but now that I'm positive the ingame settings work, this seems to be caused by some hidden setting which can't be adjusted (I've everything set to 0, including onroad). Any way to tune this down?