2 Quadraxas
i didnt worked with cars yet, but i think you can try to make wheel's mass larger than car body...

2 Cowabanga maybe))) but i like Newton more smile and somedoy worked on PhysX, as i remember smile

1st prize: Lite-C and Newton 2.17 by Vasilenko Vitaliy

Newton2 videos: http://tinyurl.com/NewtonVideos
LiteC+Newton2 discussion: http://tinyurl.com/NewtonWrapperDiscussion
Latest LiteC+Newton2 version(v23, from 29.10.2009): http://depositfiles.com/files/ae1l0tpro