ACC curbs ffb

Hello

Im trying to set up bassshakers for ACC, most of it works but there is a weird behaviour with the road rumble effect regarding curbs. When driving at high speeds there is no rumble output over simhub when going over curbs. You can hear the curb soundeffect in the audio but no rumble effect in the output graph in simhub. Grass works its only with the curbs. Is this a game limitation, since at speed lower then 80 kph it does rumble? Can anyone reproduce this? I tried to play with the max rumble speed setting, but no luck there either.

Thanks for any help :)!