Force on suspension when hitting a step

I’m trying to calculate the magnitude and direction of the force exerted on a wheel when encountering a step. The wheel and the steps are non-deformable.

I found two different approaches:

• energy approach, from which I can calculate the difference in speeds before and after, but I have no idea how to continue from there.
  https://engineering.stackexchange.com/questions/23524/vertical-component-of-force-for-rigid-wheel-hitting-a-step

• impulse and angular momentum, the procedure described by the user QiLinXue on the bottom of the post bellow roughly makes sense to me, but I have no idea what is the direction of the average force he calculates. I also don’t really understand what the velocity change represents.
  What is the term for “shock” absorbed by car suspension?

If anyone has any pointers how to continue from here, it would be much appreciated. I’m trying to calculate the vertical force to select the appropriate spring for the given speed.