Originally Posted by
Polaris OBark
I agree they are coupled, so that simplifies the problem. Why is the direction perpendicular to the bike frame of relevance? (Even if you really do need to treat it as a coupled, 3D system, that is hardly unusual, let alone fatally complicating.)
Coupled springs don't simplify the problem, they complicate it. For instance, a model with three uncoupled springs can be reduced to three independent 1 dimensional models. A model with 3 coupled springs cannot, in general, be reduced to simple independent models.