Hi! Just wanted to share some thoughts on your project:
First of all: nice idea, hope it works!
I see you have modeled the multibody assembly. If what you want to do is to assess the resistance of the parts, then I suggest to analyse each part separately. Start with the part that receives the tyre, fixing the support faces. Then translate the reactions as loads to the next part. In this way you will get simpler analysis (remember, divide and conquer).
If later you would like to simulate the lift/clamping behavior, then the multibody model is necessary. This is a more advanced simulation as you would have to apply physical contacts and time dependent boundary conditions. But don’t worry, it can be done.
Always start simple, then approach to the more realistic model by adding complexity in steps.
PD: By the way, 4000 lb are 1800 kg so 18 kN (give or take). I see you have 71 kN, and in three points, so 213 kN total, that’s a lot for this small part! Also, I think it would be more realistic to apply a face load where the tyre would rest.