Terrain is the only mesh that doesn't have collisions? Does it collide with level blocks?

Edit: aside from all this, there is an example of how to setup vehicle called 'knights_on_wheels.c' it can be found in 'GStudio8\samples' folder. I strongly recommend you to take a look at that. As it's nearly impossible for us to guess what's causing troubles on yourside. It's better for you to take a closer look at how (more or less) correct example works. Also, terrain details (or any other customizable visual settings of the terrain) have nothing to do with collision detection, so don't waste your time. Simply learn from the working example that engine provides.

Best regards.