Springy Truck Wheels with Physics Hinge

Hi Folks,
I am tinkering with an idea for a game,
a side ways driving game kind of.

My game will have a rough dirt road,
so I want the tyres to bounce in (Y) a little.
Like Moon Patrol did.

I have had a look at Lizard-13’s Car Physics example.
Car.zip → download/file.php?id=3502
Which I understand how it works,
is there a way to make the hinge ‘a little bit sloppy’ ?

From what I gather I cant do an easy collision mask for the road surface,
but I can put little ‘rocks’ along the way that the wheels can bounce over.

However I would like the wheels to have a bit of spring like suspension.

Any help appreciated.



EDIT: On another note if I move the terrain to the left with a force (whilst the vehicle is stationary) the wheels do not spin. This is related to how I may do procedural backgrounds.