I'm trying to make simple truck physics... and I found out that CONVEX hull doesn't work for me...

Works perfectly when I set POLY hull on, but that's for static things only...
At the end, I can't get simple truck physics to work, it's simply sucks...
I don't know, I think I'm doing everything right, but still doesn't work properly..
Here is the demo:
Track source
Still, I haven't seen proper vehicle physics made on GS by PhysX...
I've learned from Knights on wheels from samples, but it sucks as well...and it has noting to do with original version from ODE which is awesome!