Can anyone tell me what the ground clearance under the front spoiler / bumper unit should be on my :--

1993, Mercedes Benz, 320E, AMG.

I am now on my second spoiler unit, the first having been demolished by our so-called 'traffic calming' anti speed bumps.
This new unit is now grounding, which means there are lots of places I can't go !!!

Unable to get this information from Official Mercedes sources, because 'its an AMG.' !!!

Anyone else had this problem ??

__________________
ALBUK