How to model a skateboard?

I'm trying to make a very "loose" approximation of a skateboard.
The problem is that I do not really want to model the complex linkage 
between the trucks
and wheels because this causes my simulation to be too unstable.
So instead I'm just modelling it as a box with wheels that can only 
rotate in the axles axis.

I want to use the car turning model to turn the robot:
so basically you have 3 simple formulas:
change in angle of board = velocity * tan(steering angle)

How can I use ODE to simulate a body that would operate under these 
conditions.