Rigs of Rods

sounds odd... but its an open source vehicle physics simulator.
it looks like it was originally built for truck simulations, but its been expanded to do all sorts of vehicles. (Cars, planes, helicopters, boats)
http://www.rigsofrods.com
Theres some very impressive stuff in there, if you're really keen you can use its nods and beams logic to create your own chassis/suspension/steering geometries
Going to have more of a look at it when i get a chance.
it looks like it was originally built for truck simulations, but its been expanded to do all sorts of vehicles. (Cars, planes, helicopters, boats)
http://www.rigsofrods.com
Theres some very impressive stuff in there, if you're really keen you can use its nods and beams logic to create your own chassis/suspension/steering geometries
Going to have more of a look at it when i get a chance.