Well, I don't really expect you to understand unless you've tried coding a 3D graphics engine. You'll just have to take my word for it.
So far you're not really trying.
Try to really understand the diagrams in my first post. if you don't listen, you won't learn. What you are calling a steel "rim" is actually a whole wheel, and the rim itself looks nothing like a real steel rim. A steel rim follows the yellow lines in the rim editor, which you are failing to observe.
You really need to try and learn to use the rim editor and then you will find there are plenty of triangles left for your spokes.
Also, go for a walk and have a look at some real steel wheels.