Milos Cadek wrote:
I have calculated the parts alone many times using inertia relief during "development phase"
Milos,
Why have you been using inertia relief? It should be possible to constrain a single part such as these fully. As I understand it, inertia relief would be used primarily in a case where acceleration of the mass of the part itself is a significant part of the free body diagram. For your bike frame, I wouldn't expect the inertia of the parts to be significant compared to the reaction loads between the suspension and the weight / mass of the rider.