Corn-shaped detection on a vehicle

Translated question (from Japanese):

I’m trying out a vehicle and have an issue where a corn for detection appears unnecessarily. Though there is no such thing appearing when displaying collision (see the picture on the right), there seems to be a detection that is shown by purple lines (see the picture on the left).

If I enlarge the wheels in order to make the corn-shaped detection not contact the ground, the vehicle stops overturning. What is this thing that isn’t drawn for the collision? Thanks.

–Asked by jinushi

[Original Question][2]

Translation of the questioner’s comment:

When I rotate the collision, the vehicle contacts the ground properly as shown in the image below. Is there any problem with the FBX output?

[Original Comment][2]

Translation of the questioner’s comment:

The wheels in the above image don’t work properly, however.

Original Comment