Hi,
wheel, no naked edges, simple profiles rotate full.
export as dwg 2004solid, then import it, and declares invalid, why ?
wheel invalid when dwg export then import.3dm (7.0 MB)
Steve
Your tire assembly is made of of several nested Groups. This is hiding the duplicate tire surface.
UnGroup until you get down to surfaces and run SelDup.
Delete the duplicate tire surface.
Hi, got it 
had a duplicate tyre part.
all, others were ok, just my luck, didnt spot that.
Steve
I didn’t see it right off either.
Once I drilled down through the groups, I was selecting, Exploding, and Joining making sure that the joining tolerance has not been exceeded.
When I selected the tire, Rhino wanted to know which one.
Bingo