ok guys i have this rim and one face detached but when i try to join all the objects the weiredest thing happens, anyone wants to help just open the file and try to join all the faces and you will see, almost like a weired web comes over the object8.3dm (1.0 MB) 
You’re getting a bad render mesh because some skinny little surface slivers are more than the mesher can handle. Here’s an image of one of the problem areas:
If the model were changes to eliminate these little slivers so it looked more like this then the mesher would be happier:
Thanks john, that did it