I see that you are using a concentrated force applied to a face. Make sure it’s what you want to achieve: Don't apply concentrated force load to surfaces
Regarding BCs, you could cut it in half in the XZ plane and apply symmetry BCs there. Then you could try something like this for now:
wheel on channel rail mod.pmx (7.7 MB)
The required prescribed displacement value can be determined iteratively by checking the reaction force (requested as output in the attached file).
Just consider how you want to constrain the wheel, e.g. if it should be able to deform in the X direction.