I hit this thread 10 times while trying to figure stuff out, so if you are looking like me this might help.
One of the tutorials I was looking over was probably dated and that’s where my problem started.
If your custom righ is mysteriously floating but collision looks right just try and check the wheel blueprint again.
The value of the wheel is Radius and not Diameter. (As it very clearly states).
The issue in depth:
Unckecking the “update collision” checkbox shows the collision where you locked it via the entered values.
That gives you the impression everything is correct, but the car won’t touch the ground because the invisible wheel asset is 2x the size it should be if you typed in a diameter instead of a radius.
Stupidest issue to have, but it drove me up a wall for 2 days thinking the issue was the FBX… hopefully this helps someone in the same boat as me from pulling out hair 